Hierarchical design and scalable production of radiative cooling film featuring multispectral camouflage

Domain: physics
Published: 2026-02-02
Editorial outcome: major_revision

Abstract
Various outdoor scenarios demand both temperature control and self-protection from environment, which are often contradictory from the optical perspective, thus inspiring many material designs on multispectral camouflage and radiative cooling performance. However, these methods on the basis of one-dimensional photonic crystals or meta-surfaces always rely on stringent fabrication and may result in strong angular dependence. Here, we demonstrate an aluminum-polyamide 66 metal-based polymer bilayer thin film through hierarchical design at both the molecular and microscale levels and scalable production, enabling camouflage in infrared (3-5 μm and 8-14 μm) and laser (10.6 μm) bands with efficient radiative cooling in the non-atmospheric window (5-8 μm and 14-20 μm) while possessing weak angular dependence between −60° to 60°. Furthermore, our films can be tailored with specific emissivity and color to balance camouflage and cooling across diverse environments. This work provides a scalable, low-cost radiative cooling polymer film, advancing practical solutions for multispectral camouflage.

Introduction
Under various outdoor scenarios, appearance or optical properties of objects (human, animals, facility, etc) often need to serve two major purposes, cooling comfort and self-protection from environment, at the same time. Both of them are crucial in modern society that cooling technology is beneficial amidst the escalating impacts of global warming and rising peak daytime temperatures1,2 while camouflage provides protection, just as animals disguise themselves against predators 3–7. However, these two requirements are often contradictory, as they share similar wave bands.

As a typical example, radiative cooling and infrared camouflage both cover mid-infrared band (MIR band, 2.5–20 μm) but require different optical properties. To achieve great cooling performance, radiative cooling materials efficiently emit heat into the outer space (~3 K) through the atmospheric transparency window (3–5 μm and 8–14 μm) and exchange heat with the ambient (~298 K) through the non-atmospheric transparency window (5–8 μm and 14–20 μm) by infrared thermal radiation. Recently, radiative coolers have been widely used in various fields such as fabric8, building9,10, glacier conservation11, and electronic equipment12. For personal thermal management, radiative cooling textiles have gradually moved from research to practical use, with advanced structures including hierarchical fiber membrane13, bump textured structure14, particle distributed system15 and photon-engineered optical device like the broadband or selective emitters16. However, high infrared radiation in the atmospheric transparency window of materials indicates distinct signal in thermal imagers, which is not beneficial to infrared camouflage. Especially for objects between 30 and 100 °C such as human bodies17,18, electronic equipment19, base stations20, and tent camps21, they can be easily detected as primary targets due to their elevated temperature and emissivity different from the background, as dictated by Stefan-Boltzmann law. Infrared stealth fabrics have also been studied with several representative strategies like reducing the infrared emissivity or the temperature of the surface. The infrared optical performance regulation often relies on materials like metals, semiconductors and MXenes with broadband low emittance, while surface temperature can be controlled by thermal insulation material like aerogel and hollow structure22–24. However, these two methods will both cause thermal discomfort in the human body due to their poor heat dissipation in radiative and conductive capacity, respectively. Therefore, it is essential to develop camouflage materials that not only suppress infrared signatures but also maintain radiative cooling performance in the non-detection window.

With the development of diversified detection technologies combining thermal imagers, laser detectors, and visible telescopes25,26, it is urgent to realize multispectral compatible camouflage across different bands from various viewing angles. For this purpose, first, the ideal stealth target should have low emittance in the mid-wavelength infrared (MWIR, 3–5 μm) and the long-wavelength infrared (LWIR, 8–14 μm) to minimize thermal radiation contrast with the background in the atmospheric window24,27–30. Second, high absorbance at 10.6 μm is required for laser camouflage to interfere with the laser detector receiving a back signal31,32. In addition, the color of the stealth object in the visible band (Vis band, 0.38–0.78 μm) should be consistent with that of the background33,34. Lastly, it should have high emittance in the non-atmospheric window (5–8 μm and 14–20 μm) for radiative cooling to alleviate thermal issues as clarified above35–42. Figure 1a illustrates the ideal spectrum of camouflage from the Vis to MIR band. Such selective spectra have been previously realized through top-down methods such as one-dimensional photonic crystals or meta-surfaces43–47. These complex optical structures typically not only require stringent top-down fabrication processes with nanometer precision, but also lead to high angular dependence.

Here, through the hierarchically cross-scale design both at the molecular-level and micro-structure, we demonstrate an aluminum-polyamide 66 metal-based polymer bilayer thin film (X-film) by a scalable roll-to-roll electrospinning method that can simultaneously achieve MIR/laser camouflage and radiative cooling well matched with the ideal spectrum. Additionally, it also exhibits weak angular dependence between −60° to 60° in the mid-infrared band due to its randomly stacked structure. A series of samples with different thicknesses in field tests exhibited varying degrees of MIR camouflage while achieving a cooling temperature of 5–10 °C compared with conventional materials with broadband low emittance. Laser camouflage performance is also verified by a simulation experiment. Therefore, this hierarchical X-film with multispectral camouflage and radiative cooling can be well-designed in the face of the varying environmental conditions, providing a scalable, low-cost, and sustainable alternative to the conventional stealth scheme (Supplementary Table 1).

Results
Hierarchical design
The randomly stacked structure always exhibits no optical orientation in a specific direction, thus contributing to uniform color like white or dark in appearance such as nanofiber membranes or porous coatings48. It is not only suitable for visible band, but also creates possibilities for an infrared performance scheme with weak angle dependence. However, current materials are usually highly emissive in the mid-infrared band, not satisfying the requirements on multispectral camouflage above. Hence, to achieve low emissivity in MWIR and LWIR with weak angle dependence (Fig. 1b), it is vital to seek elaborate molecular-level design on appropriate material.

Polymers are made up of the basic chain and various functional groups which are the foundation classification of organics (Fig. 1c). Further, functional groups consist of different atoms with diverse bond combinations whose vibration mostly determines the mid-infrared absorption spectrum (Fig. 1d)13,49. Thus, we plot the MIR distribution of possible absorption peaks in 18 common organic compounds (alkyl, olefin, alkyne, arene, halohydrocarbon, alcohol, phenol, ether, aldehyde, ketone, carboxylic acid, ester, anhydride, acid halide, amide, nitrile, nitryl and amine) composed of carbon, hydrogen, oxygen, nitrogen and halogen elements (Fig. 1e, Supplementary Table 2 and Supplementary Note 1)50–54. To satisfy the requirements of multispectral camouflage in Fig. 1a, the polymers should consist of functional groups that have absorption peaks in the range of 2000–1250 cm−1 and 714–500 cm−1 (equivalent to 5–8 μm and 14–20 μm) while possess none or weak absorption in the other MIR band (3–5 μm and 8–14 μm) firstly. Therefore, amide and ketone possess the most appropriate functional groups. Alkyl is also taken into account in polymer composition because it acts as the basic element to make up long chains. In summary, the ideal polymer for multispectral camouflage is preferably comprised of alkyl, acylamino, and carbonyl. It is expected that polyamide, also named nylon, meet the requirements above very well55,56. The MIR spectrum of polymers is also affected by the absorption peak from crystallization or hydrogen bond interaction in the fabrication process56–59. Hence, in simultaneous consideration of laser camouflage at 10.6 μm (~943 cm−1), polyamide 66 (nylon 66 or PA66), which has crystalline peak at 935 cm−1 that are more closely to 10.6 μm in comparison with other polyamides like PA6, PA11 and PA12 verified by both references and experimental measurement (Supplementary Fig. 1)60–62, presents the most desirable absorption band close to the selective MIR spectrum in Fig. 1a.

Fabrication and characterization
With the significant advancement on electrostatic spinning, large-scale films can be produced by a roll-to-roll strategy. Figure 2a shows a flexible meter-scale X-film that exhibits white color and selectively emits infrared light on 5–8 μm and 14–20 μm. Specifically, the absorption property of PA66 and the scattering effect of the plicated aluminum foil substrate jointly contribute to the laser camouflage at 10.6 μm. The fiber diameter of PA66 film was controlled at ~100 nm shown in Fig. 2b so that it would not contribute to the scattering efficiency in the MIR band according to Mie theory, which is further verified by the detailed calculation in Fig. 2c (Supplementary Note 2). Thus, the MIR spectrum of PA66 film is mostly decided by its vibrational absorptions. Note that the FTIR spectrum of PA66 showed its characteristic absorption peak at 1630 cm−1 (amide band Ⅰ), 1534 cm−1 (amide band Ⅱ), 1274 cm−1 (amide band Ⅲ), 935 cm−1 (crystalline peak), 685 cm−1 (bending vibration of N-H) and 577 cm−1 (bending vibration of C=O) (Supplementary Fig. 1), which is consistent with the screening result in Fig. 1e.

Then, we fabricated a series of aluminum-PA66 metal-based polymer bilayer thin films with different thicknesses, named as XN film that N means the thickness of PA66 film. The thickness of the aluminum foil substrate is 25 μm. Figure 2d shows the optical spectrum of the X-films with varying N, with a low emissivity in MWIR and LWIR, high emissivity outside the atmospheric transparency window, and high absorbance at 10.6 μm, ideal for multispectral camouflage and radiative cooling. The MWIR/LWIR reflection varies from 96.0%/92.5% to 80.7%/59.3% against the thickness of PA66 film from 15 μm to 75 μm, which presents a relationship of gradient descent (Supplementary Fig. 2, Supplementary Note 3 and Supplementary Table 3).

A theoretical model based on the structure of X-films was further constructed to evaluate the angular sensitivity on the spectrum of X-films. It demonstrated that the reflection varied a little when the angle changed from −60° to 60° in both MWIR and LWIR, which indicated the infrared camouflage potential at a broad detection viewing angle range (Fig. 2e and Supplementary Note 4). Then, take X30 for example, we monitored the angle-dependent reflection spectrum in the LWIR. It is found that the positions of absorption peaks (especially in 10.6 μm) and overall reflection intensity are nearly unchanged between 10° to 60° of angles, suggesting that the spectrum of X-films has a weak angular dependence, which is significant for practical applications since the observation angle of infrared camera varies greatly in the processing of moving (Fig. 2f).

Considering visible camouflage, we loaded pigments on the X-films by a scalable spraying process (Supplementary Fig. 3). As shown in Supplementary Fig. 4, the pigments should selectively absorb visible light complementary to the desired color while having no effects on the MIR property of X-films, especially having no absorbance in MWIR and LWIR so that it can achieve infrared, laser, visible camouflage, and radiative cooling simultaneously. Iron oxide (Fe2O3), α-hydroxyl oxidize iron (α-FeOOH), and ferric ferrocyanide (Fe4[Fe(CN)6]3) were selected as three primary colors (red, yellow, and blue, respectively) due to their weak absorption in the MWIR and LWIR (Supplementary Fig. 5). The as-prepared films in various colors were exhibited in Fig. 2g, showing white, red, brown, yellow, cyan, blue, and dusty blue from left to right. White is the bottom color of X-films and red, yellow, blue are basic colors by adding a single pigment. Brown, cyan, and dusty blue are secondary colors by mixture of two in the three primary colors. Then, we measured the MIR spectrum (Fig. 2h) and visible spectrum (Supplementary Fig. 6) of X-films with three primary colors. The MIR spectra kept a similar trend with the spectrum in Fig. 2d, maintaining high reflectance in 3–5 μm and 8–14 μm, high emittance in 5–8 μm and 14–20 μm, and high absorbance at 10.6 μm. The visible spectra revealed the dominant reflection peaks around 750 nm, 600 nm, and 450 nm, matching the colors of red, yellow, and blue, respectively, which were further shown in the CIE color space plot (Fig. 2i). The colored X-films gradually darkened as the concentrations of pigments increased, while remaining the selective spectra in the MIR wavelength range and corresponding reflection peaks in the visible wavelength range (Supplementary Figs. 7–9). This spectral property had also been verified effective in X-films with other colors such as brown, cyan, and dusty blue (Supplementary Fig. 10).

Multispectral camouflage, radiative cooling performance and increased durability
The MIR camouflage and radiative cooling effects of the X-films were then evaluated via indoor experiments firstly. A heating sheet connected with X-films by thermal compounds was designed as an experimental setup, which is insulated from heat conduction by foam. X-films with different thicknesses of PA66 (X30, X45, X62, X72), an aluminum foil (X0), and a case without any covering (bare) were used as controls (Fig. 3a and Supplementary Fig. 11) while the initial temperature of heating sheets before covering is set as 55 °C. The infrared photographs in LWIR indicated that compared with the bare control, all X-films exhibited different potentials of camouflage performance (Fig. 3b). The stealth effect became better with the thinning of PA66 film and the aluminum foil showed the most complete camouflage due to its low-emissivity. The same trend was also demonstrated in MWIR photographs (Fig. 3c). However, the MIR property of aluminum foil is broadband low emissive so that it possessed a temperature increase of 15 °C in comparison with initial state when covered on the heating sheet, which may cause thermal problems or extra cooling energy consumption (Supplementary Fig. 12 and Fig. 3d). X-films are expected to alleviate this phenomenon because they had a cooling temperature of 5–10 °C compared to X0. Contrary to the relation between camouflage performance and the thickness of PA66 film, the heat dissipation capacity of X-films was correlated positively with the thickness of PA66 film, where it existed a balance. Thus, in situations where stealth is not as demanding, various X-films can be selected to meet the basic requirements on camouflage and further enlarge cooling performance. Then, a heating power test was also conducted to demonstrate the MIR property of different controls (Fig. 3e). To maintain the temperature of the heating sheet at 55 °C, the bare control demanded the heating power up to 428 W m−2 due to its high MIR emissivity while the case covered with X0 film required the lowest (272 W m−2). The controls with X-films fell in between (316 W m−2, 336 W m−2, 362 W m−2, and 374 W m−2 for X30, X45, X60, and X72, respectively) by virtue of their great radiative cooling performance in the non-atmospheric window. Thus, both the temperature test and heating power test verify that X-films can achieve MIR camouflage and radiative cooling effects, which are corresponding to the optical spectra above.

We also evaluated the camouflage and cooling performance using the same device outdoors at night. It could focus more on the MIR spectrum because there was no sunlight to bring the extra energy input. In comparison with indoors, convection was also taken into consideration to reflect the actual situation outdoors. Similarly, all the X-films exhibited good stealth effects and the trend with the thickness of PA66 film was consistent with the indoor test (Supplementary Fig. 13). In the temperature test, the cases with X30, X45, X62, and X72 film were 5 °C, 9 °C, 10 °C, and 12 °C cooler than the case with X0 film, respectively, showing good cooling capacity as well (Supplementary Fig. 14). Then, we further assessed the temperature control of X-films under solar exposure. The nylon fiber can scatter solar radiation by Mie theory, thus exhibiting high reflectivity in solar band (Supplementary Fig. 15). During the field temperature test in the daytime, the cases with X45 and X72 films were 7 °C and 11 °C cooler than the case with X0 film, maintaining superior cooling performance. All the results consistently demonstrate the splendid properties of X-films, further illustrating the importance of material selection on PA66.

To demonstrate the weak angular dependence of X-films, infrared photographs in different observation angles between 10° to 60° were captured. An X30 sample with the dimension of 3 cm * 3 cm is tightly connected with a heater whose temperature is ~75 °C. We ensured the precise observation angles by holding the infrared camera still and rotating the heating sheet to the corresponding angles. It is found that the colors of the sample remain nearly unchanged between 10° to 60°, suggesting that the X-films have weak angular dependence and exhibit great camouflage performance in varying observation angles (Fig. 3f).

Having verified the infrared camouflage and radiative cooling capacity of X-films, it is important to evaluate the other requirements such as laser camouflage. We designed an indoor simulated experiment against the outdoor test to demonstrate the laser camouflage effect that less back signal received means better laser camouflage. As shown in Fig. 3g, a quantum cascade laser was used to emit light at 10.6 μm and the strength of the back signal was recorded by an optical power meter. Samples with PA66 spun on the smooth aluminum plates and on the plicated aluminum foils were used to clarify the influences on laser camouflage by the absorbance of the PA66 layer and the Geometric scattering effect of substrates at 10.6 μm, respectively (Supplementary Fig. 16). As shown by optical path transmission schematic in Supplementary Figs. 17 and 18, the sample with absorption or scattering effect both can weaken the received signal strength in the optical power meter. The detailed results illustrated that the reflection strength of the back signal of X-films with different thicknesses of PA66 films on the plicated aluminum foils decreased rapidly compared to bare aluminum foils under the combined action of absorption and scattering, which all exhibited good laser camouflage potential (Fig. 3h).

Durability is also an important problem in practical applications. X-films have good mechanical properties under mechanical stress (Supplementary Figs. 19 and 20). For further optimization, we increased the stability of X-films by polyethylene (PE) film encapsulation on the surface, named as XNP film (N means the thickness of PA66 film). Figure 3i demonstrated that the curve shapes of MIR spectra were similar between XNP film and XN film because polyethylene showed high mid-infrared transmission which has only C-C and C-H bonds. Then, a series of tests were conducted to verify the environmental durability, including low-temperature tests, high-temperature tests, acid tests, alkali tests, water flushing tests, UV exposure tests, and wind tests. The mass changes were less than 1.0% after each of these seven tests, indicating the films were well preserved (Fig. 3j). Additionally, the reflection in LWIR also remained nearly unchanged so that the MIR property of XNP films would work for a long time (Fig. 3k and Supplementary Fig. 21). The scratch and abrasion resistance test also verified that the XNP film possessed good durability (Supplementary Figs. 22 and 23). These satisfactory results all illustrate that the durability of XNP films has been increased, which is expected to stand up to practical use.

Well-designed camouflage
It is common to carry electronic equipment like batteries or communication devices on a few-day journey. Thus, when encountering unexpected surveillance in the field, timely camouflage against visible and infrared detection is necessary due to the vivid color differences in optical photographs and the temperature-induced contrasts (~37 °C for human body and more than 70 °C for electronic equipment while 20 °C for environment) in infrared image in comparison with background. Meanwhile, efficient radiative cooling performance is beneficial to humans on long-term standby and devices in prolonged operation, which is mainly focused on non-atmospheric window (5–8 μm and 14–20 μm) when satisfying infrared camouflage. Additionally, it is necessary to decrease the back signal strength at 10.6 μm for laser camouflage.

Then, cotton woven fabrics attached by X-films (X-fabric) and aluminum films (Al-fabric) were worn on dummies with heating sheets on the main parts such as chest and abdomen for temperature regulation as a comparison to clarify the multispectral camouflage and cooling performance. The X-fabric not only exhibited infrared camouflage effect similar with the Al-fabric (Fig. 4a) but also owned a better visible camouflage than the Al-fabric (Fig. 4b). Meanwhile, the temperatures of chest and abdomen under the X-fabric were both lower than those under the Al-fabric due to its extra radiative heat dissipation capacity in the non-atmospheric window (Fig. 4c). The laser camouflage potential was evaluated via the detected temperature of the bright spot which was caused by the emitted light at 10.6 μm of a quantum cascade laser in the captured infrared images. Higher temperatures meant higher echoed signals, further representing lower absorptive ability and worse laser camouflage of samples. As shown in Fig. 4d, the X-fabric had a lower temperature than the Al-fabric at the same power, indicating a better laser camouflage effect. Also, the laser signal on the X-fabric disappeared in the background as the emitter power decreased from 0.1 P to 0.018 P (P stands for the original laser power) while that of the Al-fabric not, which implied that the X-fabric could suffer shorter maximum detection distance in actual use. Then, infrared images were taken from −60° to 60° at a distance of ~2 m (Fig. 4e). It was verified that the X-fabric had good infrared camouflage performance from various angles and maintained a consistent color due to its weak angular dependence, which was beneficial to flexibly cope with mobile detectors in practical applications.

The X-fabric was also well-designed by body region with different color and emissivity against various actual scenarios like shrubberies. Figure 4f presented the infrared and optical images of a human wearing garments made of three different textiles on a cloudy day. The images showed that although the green cotton fabric exhibited a similar color to the shrubberies in comparison with the white cotton fabric, it still could not achieve infrared camouflage due to its high emissivity as the same as the white cotton fabric. However, the regionalized well-designed green X-fabric displayed a similar color to the background in both infrared and optical photographs.

Additionally, the requirements on multispectral camouflage are changing for integrating into the various environmental backgrounds (Supplementary Figs. 24, 25 and Supplementary Note 5). Thus, the X-films can be well-designed by adjusting the thickness of PA66 film, the mass ratio of loaded pigments, and the selection of PE film to achieve appropriate reflectivity or emissivity for better integrating into environments (Supplementary Fig. 26 and Supplementary Note 6). The recommended thickness range of PA66 film balancing camouflage and cooling performance is from 30 μm to 75 μm. As an example, the devised brown X-film showed a similar color to sand and it could provide good infrared camouflage for electronic equipment like a fully operational mobile phone (Supplementary Fig. 27). Furthermore, the surface treatment of substrate is also beneficial for X-films to achieve better infrared camouflage performance against various surroundings63.

Methods
Fabrication of the X-films
PA66 (Rhawn, Mw = 679) was dissolved in formic acid/acetic acid with a temperature of 40 °C and magnetic stirring at 500 rpm until it formed a clear solution. The ratio of solute and solvent is 1g PA66: 2.5ml formic acid: 2.5ml acetic acid. The as-prepared solution was electrospun at a tip-to-collector distance of 15 cm, a voltage difference of 25.5 kV, and a flow rate of 0.1 ml h−1 with 18-gauge needle tips. A drum wrapped with a layer of aluminum film was used for collecting the PA66 nanofibers. The rotation speed of the collector was 80 rpm. All electrospinning experiments were conducted at a room temperature of 20 °C and a relative humidity of ~40%. The thickness of X-films was measured with a micrometer caliper which was mainly determined by spinning time. The XNP films were fabricated by XN films hot pressed with PE film (~30 μm) at 110 °C.

Fabrication of the colored X-films
The pigments (Iron oxide (Aladdin, 99.5% metals basis), α-hydroxyl oxidize iron (Sigma-Aldrich, 30–63% Fe), ferric ferrocyanide (Aladdin, biological stain)) for corresponding colors (a mixture of one or more pigments) were dispersed in ethanol by magnetic stirring and ultrasonic cleaning. The X30 films were selected as the spraying substrate. The as-prepared solution was sprayed onto the pre-heated X30 films by a spray gun (SATHN, W-71). The depth of color was determined by the mass loading of pigments that could be adjusted through spray time and spray speed. The initial mass of the X30 film was recorded as m1 and the final mass of the colored X30 film after evaporating ethanol was recorded as m2. The mass ratio of the loaded pigments ωcolor was calculated by (m2 − m1)/m2.

Material characterizations
The microscopic image of PA66 nanofibers was captured by scanning electron microscopy (SEM; TESCAN, MIRA3). The FTIR spectrum was measured by Nicolet IS10. The mid-infrared spectrum (2.5–20 μm) was measured using a Fourier transform infrared spectrophotometer (Thermo Fisher Scientific, Nicolet IS50R) loaded with an integrating sphere (Pike, 4P-GPS-020-SL). The angle-dependent mid-infrared spectrum was measured by the Fourier transform infrared spectrophotometer (VERTEX 80v, Bruker) coupled with a thermal emission collection setup while keeping different tilt angles of the tested sample. The solar spectrum (0.3–2.5 μm) was measured by an ultraviolet-visible spectroscopy (SHIMADZU, UV3600) equipped with an integrating sphere (ISR-310). The infrared photographs in 8–14 μm were captured by an LWIR camera (Fluke, TiX580). The infrared photographs in 3–5 μm were captured by a MWIR camera (Telops, FAST M200).

Measurement of radiative cooling performance and infrared camouflage performance
The temperature was monitored by K-type thermocouples and real-time recorded by a recorder (Asmik, MIKR6000C). A Kapton heater sheet was used as an internal heat source with a size of 10 cm × 10 cm. The initial temperatures of heating sheets before covering were set as 55 °C in all control groups with a heating power of ~5.2 W. The heating power test was conducted with a temperature feedback circuit. The temperature of the tested sample was controlled at 55 °C by heating. Through the temperature controller and power meter (Chroma, 66205), the heating power of the sample could be achieved, which was equivalent to radiative cooling performance. The outdoor temperature was monitored through the same method used in the indoor test as mentioned above. All the temperature tests, power tests, and LWIR image captures were conducted in Nanjing (32.12° N, 188.96° E) while the MWIR image capture was conducted in Zhejiang (30.26° N, 120.12° E).

Measurement of laser camouflage performance
A quantum cascade laser (Block Engineering, LaserTune) was controlled to emit 10.6 μm light and an optical power meter (MKS Ophir 3A) was used to record the strength of the back signal. The power of the back signal with the aluminum plate or foil was recorded as Pr. The power of the back signal with samples was recorded as Ps. The reflection strength of the back signal was calculated by Ps/Pr.

Environmental durability tests
(1) Low-temperature test: the samples were put in a freezer with a constant temperature of −40 °C for 1 week. (2) High-temperature test: the samples were put on a heating stage with a constant temperature of 80 °C for 1 week. (3) Acid test: the samples were immersed in sealed hydrochloric acid aqueous solution with pH = 4 for 1 week. (4) Alkali test: the samples were immersed in a sealed potassium hydroxide aqueous solution with pH = 10 for 1 week. (5) Water flushing test: the samples were fixed with a tilt angle of ~45° from the water faucet with a water flow rate of 50 ml s−1. The water flowed over the samples into the pool. The flushing process was 10 min. (6) UV exposure test: the samples were illuminated by a UV lamp (6 W) in a closed chamber for 1 week. (7) Wind test: the samples were fixed on a glass in front of the fan with the gas flow of 83 cubic feet per minute (CFM) for 1 h. The mass changes and spectral changes before and after the experiments above were recorded to evaluate the durability of the samples. (8) Scratch resistance test: sharpened pencils with different hardness levels were pushed on the sample’s surface to create a scratch over 1 cm in length at a 45° angle. The test was conducted until a pencil ruptured the coating, which meant the hardest pencil that did not cause rupture was recorded as the hardness level of the coating. The load weight was 500 g during the test. (9) Abrasion resistance test: a glass with the sample attached was placed upside down on the sandpaper (grit size 400). A 100 g weight was placed on the surface of the glass. The glass was moved around a 10 cm square as one cycle (from position 1 to 2 to 3 to 4 and then back to position 1). The infrared spectra and visual appearance were recorded before and after the test.

On-body camouflage effects
A volunteer wore three different textiles in front of the shrubberies, which are white cotton fabric, green cotton fabric and cotton woven fabric attached by green X-films, respectively. The optical photographs and infrared images were captured to evaluate the visible and infrared camouflage performance. Written and informed consent was received from all volunteers.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This study introduces a groundbreaking advancement in multispectral camouflage technology through a bioinspired hierarchical architecture of aluminum-PA66 bilayer films. The innovative design synergizes molecular-level functional group engineering of PA66 with microscale disordered fibrous structures, effectively resolving the inherent trade-off between radiative cooling efficiency and multispectral (infrared/laser) stealth performance. Notable achievements include demonstrated angular insensitivity of optical properties, field-validated thermal regulation with concurrent camouflage effectiveness, industrial scalability via roll-to-roll electrospinning technology, and environmental adaptability through parameter customization. The developed functional group screening methodology represents a significant contribution to polymer-based photonic material design. This work establishes a paradigm-shifting platform that integrates sophisticated optical engineering with large-scale production capabilities, offering transformative potential for thermal management and stealth applications in challenging outdoor environments. The following are my comments, with the hope of further improving the quality of the manuscript:\n1. In the Introduction section, the summary of the current research status of multispectral infrared stealth in the paper is somewhat insufficient. In fact, there have been many related studies on infrared stealth or radiation cooling fabrics in recent years. Suggest providing a more comprehensive supplementary introduction to the research status section.\n2. Fig.1b only shows weak angular correlation and cannot indicate that the structure has stealth properties. Does the invisibility mentioned here refer to the visible light spectrum? Suggest modifying the relevant description.\n3. How was the absorption peak obtained in Supplementary Fig. 2? Suggest supplementing relevant information and direct measurement data, rather than just providing the band positions of the features.\n4. Supplementary Note 4: The accuracy and feasibility of the Kubelka-Munk approximate theory model need to be discussed, especially in the calculation of angle correlation. The traditional KM theory is an approximate solution method for the radiative transfer equation based on a series of assumptions. This method cannot accurately characterize the reflectivity in different directions. It is recommended to verify this conclusion using more accurate solving methods, such as directly solving electromagnetic scattering or solving the radiative transfer equation more accurately.\n5. The paper seems to only clearly indicate the thickness of the aluminum foil in Fig.2. Suggest clearly stating the thickness of the aluminum foil used in the main text.\n6. Line 292: The introduction of a series of environmental durability tests is too brief. Suggest providing specific testing conditions and testing time, rather than just displaying results before and after.\n7. X-films are prepared by electrospinning and are actually more like porous films composed of filamentous fabrics. Can the thickness alone fully characterize this film? Additionally, can films of the same thickness prepared multiple times maintain consistent film properties?", "reviewer_2": "This work presents a manufacturable approach to multispectral camouflage through roll-to-roll fabricated aluminum-PA66 bilayer films. The material demonstrates compelling optical performance, balancing infrared stealth capabilities with radiative cooling functionality. The systematic experimental characterization provides evidence for the film's dual-mode operation across critical wavelength bands. The proposed technology shows particular idea for applications requiring adaptive thermal management and visual-infrared concealment.\n1. The manuscript presents spectral trends for X-films with varying PA66 thicknesses. Please include a consolidated summary table reporting for each thickness: (i) average emissivity in MWIR and LWIR bands, (ii) reflectance (or return signal strength) at 10.6 μm, and (iii) average emissivity in the non-atmospheric windows (5–8 μm and 14–20 μm). A recommended thickness range balancing camouflage and cooling performance should also be provided.\n2. While the study demonstrates the feasibility of color customization, the side effects of pigment loading on mid-infrared performance are not quantitatively summarized.\n3. The “plicated aluminum foil” substrate is credited with enhancing laser camouflage via scattering, but no quantitative surface morphology (e.g., roughness, wrinkle wavelength/amplitude) is provided.\n4. In Fig. 1e caption, symbols “√” and “×” are mentioned but not present in the figure.\n5. The citation for Supplementary Fig. 14 appears to refer to Supplementary Fig. 15. A thorough proofreading is needed.\n6. Mie scattering theory requires strict assumptions regarding wavelength and particle size. Given the fiber diameter (~100 nm) and MIR wavelengths (3–20 μm), the applicability of Mie theory is questionable. The authors should justify its use or employ a more suitable model to support the claim that scattering is negligible in the MIR regime.\n7. The bio-inspired aspect is underdeveloped and appears disconnected from the main technical content. The term “bio-inspired” appears in the title, but the Introduction does not adequately motivate this perspective, and the link to insect cocoons feels tenuous.\n8. The manuscript states that laser camouflage at 10.6 μm results from both PA66 absorption and substrate scattering. More detailed discussion is expected.\n9. The method of bonding between the PA66 layer and the aluminum substrate is not clearly described. The interfacial adhesion and long-term stability of the bilayer structure under mechanical stress or thermal cycling should be discussed.\n10. The study acknowledges a trade-off between MIR camouflage and radiative cooling performance depending on PA66 thickness. However, the manuscript does not sufficiently address how this trade-off limits simultaneous optimization. The research gap regarding materials that truly combine both functions without compromise is not fully resolved by this work.\n11. The claim that “the heat dissipation capacity of X-films was correlated negatively with the thickness of PA66 film” is misleading. Both experimental and spectral data show that thicker PA66 layers lead to higher emissivity in the non-atmospheric windows, which should enhance radiative cooling.", "reviewer_3": "This paper presents a composite film material for camouflage purpose with radiative cooling performance. The context is clear and the logic is smooth. Due to current technical issues in the manuscript, I suggest revision.\n1. The proposed film is “an aluminum-PA66 metal organic bi-layer thin film”. “Metal” is a noun and thus is not properly used here. Please consider another way to describe the composite film.\n2. Line 66 states that metals/semiconductors with low emittance have poor heat dissipation, which is not accurate. They have poor radiation loss but can dissipate heat by their high thermal conductivity. Please elaborate or correct the statement.\n3. Fig 1e caption: there is no √ or × in the figure.\n4. Line 131-132, please provide evidence or reference.\n5. Please provide data on mechanical properties and/or mechanical durability.\n6. Please provide performance comparison with existing literature in terms of camouflage and cooling performance.\n7. I notice some improper expressions. Please go through the manuscript to avoid such typos or mistakes.\n• Typo in line 21: “human activity” should be “human activities”.\n• Line 26: “these designs based on top-down one-dimensional photonic crystals or meta-surfaces always require”. Please check grammar.\n• Line 31: “camouflage on … bands”. “On” should be “in”.\n• Line 59: “just as animals disguise themselves to evade predators”. Please check grammar.\n• Line 61, the objects should be plural.\n8. In the introduction, the authors mention “temperature comfort” as a main purpose here, but only cooling performance is presented. No heating comfort in a cold environment is involved. Please justify this point or revise the context. Also, the authors should elaborate in the first paragraph on why the two purposes are important and why they contradict each other.\n9. What is the mechanism that PA66 is a perfect fit here rather than nylon 6, nylon 11, and nylon 12. Please explain and elaborate.\n10. For Fig 2i, a CIE color space plot should be better.", "reviewer_4": "Comments to NCOMMS-25-60184\nThis work reports a PA66 electrospinning nanofiber film combined with aluminum foil to realize a camouflage membrane. The design leverages the infrared optical properties of nylon66, achieving the desired high reflectance in the 3–5 μm and 8–14 μm atmospheric windows while maintaining strong absorption in other thermal infrared bands, thus offering a low-cost stealth solution. Moreover, the absorption peak of nylon 66 at 10.6 μm—though relatively weak and of questionable effectiveness—may impart some capability for laser detection stealth. It should be noted that the core material, electrospinning nylon nanofibers, has previously been reported in the Nature Communications (doi.org/10.1038/s41467-025-57366-9) for radiative cooling textiles, with quite similar material properties. This study, however, nicely repurposes those same infrared optical characteristics for stealth applications and investigates them in detail. However, the idea of camouflaging and radiatively cooling hot objects by emission in the 5-8 and > 13 μm is a well known idea, with several papers detailing this concept reported in the literature. Therefore, from both a material and conceptual standpoint, the work appears to have limited novelty. Furthermore, the cooling ability of this design is likely limited because of its emittance outside the window. On the scalability front, this is a nice advance, but perhaps more suited for a more discipline specific journal. \nSpecific comments on the manuscript are as follows:\n1. Nylon fibers as a longwave transmissive but otherwise thermally emissive material has been previously discussed by others.1,2 So materially, this is not very new, even though the authors detail the properties of nylon. This was discussed as early as 2015.\n2. The idea of combining radiative cooling with camouflage has been quite well explored. See, for example, H Zhu et. al., Nat Comm, 12(1), 2021. Deng et. al, Adv. Func. Mat., 2500122, 2025, and Wang et. al., Opt Mat Express, 13(10), 2023. The authors’ material is likely more scalable than some of the previously deployed designs, and potentially better for humans. But the concept is known.\n3. For humans, is radiative cooling outside the LWIR window practical? Previous works have shown that outside the window, humans gain rather than lose heat.3 Indeed for vertical surfaces, it seems that it is better to have the opposite spectral profile of what the authors suggest.4 Thus, the cooling ability of the design seems to be limited.\n4. Frankly, the use of “Bio-inspired” in the title seems somewhat overstated. Although the design is described as inspired by cocoons, cocoons do not function by reflecting infrared radiation for camouflage, so the connection in terms of functionality or material design is weak.\n5. While electrospinning can indeed be scaled to roll-to-roll production, the manuscript does not actually demonstrate any roll-to-roll process. It may be advisable to reconsider how this is framed in the title.\n6. The work does not present any solar reflection data. Since aluminum absorbs to some extent in the UV–visible range and has low thermal emissivity, it tends to heat up under sunlight. If the nylon fiber layer can scatter solar radiation and significantly reduce absorption by the aluminum foil, this would be highly beneficial for practical temperature control under solar exposure. Based on only the modest thermal emittance in the non-atmospheric window, the cooling effect in the outdoor may not be so ‘efficient’ as claimed in the Abstract.\n7. Camouflage by reflection is tricky, because the reflected temperature has to be the same as the background temperature. Given that the average diameter of the nylon fibers is only 0.1 μm, one can infer that they are transmissive in the longwave IR, i.g. reflection by the underlying Al is primarily specular. For example, in Fig. 4f, the cold infrared signal observed at the shoulder may originate from reflection of the sky’s thermal radiation. But does it not stand out from the warm background, defeating the very point of the design? This is a potential issue worth discussing. Surface treatments of the aluminum foil could perhaps mitigate this problem.\n8. There seems to be a clear tradeoff between LWIR camouflage and laser reflection at 10.6 μm. Can the design proposed by the authors simultaneously do both well? That seems a somewhat doubtful.\n9. Does thermal camouflage and laser camouflage collectively qualify as multispectral camouflage? The first is multispectral for their design, and the second actually occurs within the LWIR. So line 275 of their manuscript should be edited accordingly.\n10. Is is not more likely for technologies like LIDAR (cheaper light sources and detectors) to be used to detect humans rather than 10.6 μm lasers (LWIR reflective camouflage gear seems a relatively unused concept)? If yes, then would this textile not be counterproductive?\n1. Tong, J. K. et al. Infrared-Transparent Visible-Opaque Fabrics for Wearable Personal Thermal Management. ACS Photonics 2, 769–778 (2015).\n2. Chen, Z. et al. An infrared-transparent textile with high drawing processed Nylon 6 nanofibers. Nat Commun 16, 2009 (2025).\n3. Wu, R. et al. Spectrally engineered textile for radiative cooling against urban heat islands. Science 384, 1203–1212 (2024).\n4. Xie, F. et al. Subambient daytime radiative cooling of vertical surfaces. Science 386, 788–794 (2024).", "reviewer_5": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Response to Reviewer #1\nThis study introduces a groundbreaking advancement in multispectral camouflage\ntechnology through a bioinspired hierarchical architecture of aluminum-PA66 bilayer\nfilms. The innovative design synergizes molecular-level functional group engineering\nof PA66 with microscale disordered fibrous structures, effectively resolving the\ninherent trade-off between radiative cooling efficiency and multispectral (infrared/laser)\nstealth performance. Notable achievements include demonstrated angular insensitivity\nof optical properties, field-validated thermal regulation with concurrent camouflage\neffectiveness, industrial scalability via roll-to-roll electrospinning technology, and\nenvironmental adaptability through parameter customization. The developed functional\ngroup screening methodology represents a significant contribution to polymer-based\nphotonic material design. This work establishes a paradigm-shifting platform that\nintegrates sophisticated optical engineering with large-scale production capabilities,\noffering transformative potential for thermal management and stealth applications in\nchallenging outdoor environments. The following are my comments, with the hope of\nfurther improving the quality of the manuscript:\nResponse:\nWe very appreciate the Reviewer #1 for the great efforts on this manuscript. We\nare delighted that the reviewer recognizes that “The innovative design synergizes…\nNotable achievements include… The developed functional group screening\nmethodology represents a significant contribution to… This work establishes a\nparadigm-shifting platform that…”. Below, we present our detailed point-by-point\nresponses to all the constructive comments and suggestions.\n1. In the Introduction section, the summary of the current research status of\nmultispectral infrared stealth in the paper is somewhat insufficient. In fact, there have\nbeen many related studies on infrared stealth or radiation cooling fabrics in recent years.\nSuggest providing a more comprehensive supplementary introduction to the research\nstatus section.\nResponse:\nWe thank the reviewer for this helpful suggestion. A more comprehensive\nsupplementary introduction has been revised to the research status section on infrared\nstealth and radiation cooling fabrics in recent years.\nPage 3, Line 44\n“Under various outdoor scenarios, appearance or optical properties of objects (human,\nanimals, facility, etc) often need to serve two major purposes, cooling comfort and self-\nprotection from environment, at the same time. Both of them are crucial in modern\nsociety that cooling technology is beneficial amidst the escalating impacts of global\nwarming and rising peak daytime temperatures 1-2 while camouflage provides\nprotection, just as animals disguise themselves against predators 3-7. However, these\ntwo requirements are often contradictory, as they share similar bandwidth.\nAs a typical example, radiative cooling and infrared camouflage both cover mid-\ninfrared band (2.5-20 μm) but require different optical properties. To achieve excellent\ncooling performance, radiative cooling materials efficiently emit heat into the outer\nspace (~3 K) through the atmospheric transparency window (3-5 μm and 8-14 μm) and\nexchange heat with the ambient (~298 K) through the non-atmospheric transparency\nwindow (5-8 μm and 14-20 μm) by infrared thermal radiation. Recently, radiative\ncoolers have been widely used in various fields such as fabric 8, building 9,10, glacier\nconservation 11, and electronic equipment 12. For personal thermal management,\nradiative cooling textiles have gradually moved from research to practical research,\nwith advanced structures including hierarchical fiber membrane 13, bump textured\nstructure 14, particle distributed system 15 and photon-engineered optical properties like\nbroadband or selective emitters 16. However, high infrared radiation in the atmospheric\ntransparency window of materials indicates distinct signal in thermal imagers, which\nis not beneficial to infrared camouflage. Especially for objects between 30 ℃ and 100 ℃\nsuch as human bodies 17,18, electronic equipment 19, base stations 20, and tent camps 21,\nthey can be easily detected as primary targets due to their elevated temperature and\nemissivity different from the background, as dictated by Stefan-Boltzmann law. Infrared\nstealth fabrics have also been studied with several representative strategies like\nreducing the infrared emissivity or the temperature of the surface. The infrared optical\nperformance regulation often relies on materials like metals, semiconductors and\nMXenes with broadband low emittance, while surface temperature can be controlled\nby thermal insulation material like aerogel and hollow structure 22-24. However, these\ntwo methods will both cause thermal discomfort in the human body due to their poor\nheat dissipation in radiative and conductive capacity, respectively. Therefore, it is\nessential to develop camouflage materials that not only suppress infrared signatures\nbut also maintain radiative cooling performance in the non-detection window.\nWith the development of diversified detection technologies combining thermal imagers,\nlaser detectors, and visible telescopes 25,26, it is urgent to realize multispectral\ncompatible camouflage across different bands from various viewing angles. For this\npurpose, first, the ideal stealth target should have low emittance in the mid-wavelength\ninfrared (MWIR, 3-5 μm) and the long-wavelength infrared (LWIR, 8-14 μm) to\nminimize thermal radiation contrast with the background in the atmospheric window\n27-31. Second, high absorbance at 10.6 μm is required for laser camouflage to interfere\nwith the laser detector receiving a back signal 32,33. In addition, the color of the stealth\nobject in the visible band (Vis band, 0.38-0.78 μm) should be consistent with that of the\nbackground 34,35. Lastly, it should have high emittance in the non-atmospheric window\n(5-8 μm and 14-20 μm) for radiative cooling to alleviate thermal issues as clarified\nabove 36-43. Fig. 1a illustrates the ideal spectrum of camouflage from the Vis to MIR\nband. Such selective spectra have been previously realized through top-down methods\nsuch as one-dimensional photonic crystals or meta-surfaces 44-48. These complex\noptical structures typically not only require stringent top-down fabrication processes\nwith nanometer precision, but also lead to high angular dependence.”\n2. Fig.1b only shows weak angular correlation and cannot indicate that the structure has\nstealth properties. Does the invisibility mentioned here refer to the visible light\nspectrum? Suggest modifying the relevant description.\nResponse:\nWe are very sorry for the misleading. Fig. 1b is used as illustration to show weak\nangular correlation and emphasize on invisibility in the infrared spectrum. We have\nadded a schematic in material structure and optical performance as shown in Fig. R1.\nFig. R1. A schematic of the revised Fig. 1b. Page 6 in the revised manuscript.\nTo clarify the problem, we have revised the manuscript as follows:\nPage 5, Line 108\n“The randomly stacked structure always exhibits no optical orientation in a specific\ndirection, thus contributing to uniform color like white or dark in appearance such as\nnanofiber membranes or porous coatings 49. It is not only suitable for visible band, but\nalso creates possibilities for an infrared performance scheme with weak angle\ndependence. However, current materials are usually highly emissive in the mid-\ninfrared band, not satisfying the requirements on multispectral camouflage above.\nHence, to achieve low emissivity in MWIR and LWIR with weak angle dependence (Fig.\n1b), it is vital to seek elaborate molecular-level design on appropriate material.”\nPage 7, Line 144\n“(b) Schematic of micro-structure of the fibrous membrane. The randomly stacked\nstructure on substrate brings low emissivity in MWIR and LWIR with weak angular\ndependence.”\n3. How was the absorption peak obtained in Supplementary Fig. 2? Suggest\nsupplementing relevant information and direct measurement data, rather than just\nproviding the band positions of the features.\nResponse:\nThanks very much for this kind reminder and we apologize for the misleading.\nOriginal Supplementary Fig. 2 is aimed at exhibiting the position of crystalline\nabsorption peak of nylon 6, nylon 66, nylon 11 and nylon 12 to estimate the best suitable\nmaterial for laser camouflage at 10.6 μm, where the data is obtained from the reported\nliteratures [1-4]. To further verify the infrared properties of these features, we measured\nthe FTIR spectra of PA6, PA66, PA11 and PA12 (Fig. R2) and they agree well with\nresults from literatures.\nFig. R2. FTIR spectra of PA6, PA66, PA11 and PA12. The crystalline peak of PA6 is at\n930 cm-1 and 960 cm-1. The crystalline peak of PA66 is at 935 cm-1. The crystalline\npeak of PA11 is at 582 cm-1, 628 cm-1 and 688 cm-1. The crystalline peak of PA12 is at\n580 cm-1, 626 cm-1 and 681 cm-1. The crystalline peak of PA66 is closer to the laser\nband (10.6 μm).\nThis is also the new Supplementary Fig. 1 in the revised manuscript (Page 10).\nTo clarify this problem, we have revised the manuscript as follows:\nPage 5, Line 134\n“Hence, in simultaneous consideration of laser camouflage at 10.6 μm (~ 943 cm-1),\npolyamide 66 (nylon 66 or PA66), which has crystalline peak at 935 cm-1 that are more\nclosely to 10.6 μm in comparison with other polyamides like PA6, PA11 and PA12\nverified by both references and experimental measurement (Supplementary Fig. 1) 61-\n63, presents the most desirable absorption band close to the selective MIR spectrum in\nFig. 1a.”\n[1] Y. Ma, T. Zhou, G. Su, Y. Li, A. Zhang, Understanding the crystallization behavior\nof polyamide 6/polyamide 66 alloys from the perspective of hydrogen bonds: projection\nmoving-window 2D correlation FTIR spectroscopy and the enthalpy. RSC Adv. 6,\n87405-87415 (2016).\n[2] G. Zhang, Y. Li, D. Yan, Polymorphism in nylon-11/montmorillonite nanocomposite.\nJ. Polym. Sci. Pt. B-Polym. Phys. 42, 253-259 (2004).\n[3] N. Ma et al., Crystal transition and thermal behavior of Nylon 12. e-Polymers 20,\n346-352 (2020).\n[4] N. Vasanthan, D. Salem, Infrared spectroscopic characterization of oriented\npolyamide 66: band assignment and crystallinity measurement. J. Polym. Sci. Pt. B-\nPolym. Phys. 38, 516-524 (2000).\n4. Supplementary Note 4: The accuracy and feasibility of the Kubelka-Munk\napproximate theory model need to be discussed, especially in the calculation of angle\ncorrelation. The traditional KM theory is an approximate solution method for the\nradiative transfer equation based on a series of assumptions. This method cannot\naccurately characterize the reflectivity in different directions. It is recommended to\nverify this conclusion using more accurate solving methods, such as directly solving\nelectromagnetic scattering or solving the radiative transfer equation more accurately.\nResponse:\nThank you very much for the pertinent comment. The calculation method used\nhere is not the “traditional KM theory”, but based on hyperbolic solutions of radiative\ntransfer equation for planar films with isotropic scattering. Hence, the primary\napproximation is the isotropic scattering of the scatterer, resulting in the direction\nindependent and incoherent scattering waves. This approximation is reasonable for a\nhighly scattered nanofiber-based medium, which has been widely tested and employed\nto evaluate the reflection and transmission through nanofibers-based turbid media [1-\n2]. More details on this method can be checked in the original paper [3].\nThe phase function is a constant (correlated to scattering and absorption\ncoefficients) for an isotropic scatterer. As a result, the phase of scattered wave is\nindependent of scattering directions. In the calculation, only incident angle is involved\nsince the light propagation distance of in the film is proportional to . In other\nwords, for the oblique incidence, the effective film thickness is large1r ⁄thcaons t𝜃𝜃he normal\nincidence, enhancing the reflection or transmission.\n[1] Y. Lim, J. Jin, B. Bae, Optically transparent multiscale composite films for flexible\nand wearable electronics. Adv. Mater. 32, 1907143 (2020).\n[2] X. Li et al., Strain-adjustable reflectivity of polyurethane nanofiber membrane for\nthermal management applications. Chem. Eng. J. 461, 142095 (2023).\n[3] K. Klier, Absorption and scattering in plane parallel turbid media. J. Opt. Soc. Am.\n62, 882-885 (1972).\n5. The paper seems to only clearly indicate the thickness of the aluminum foil in Fig.2.\nSuggest clearly stating the thickness of the aluminum foil used in the main text.\nResponse:\nWe appreciate the reviewer’s reminder. The thickness of the aluminum foil used\nin this work is all 25 μm and we have revised the manuscript to state it clearly.\nPage 7, Line 172\n“Then, we fabricated a series of aluminum-PA66 metal-based polymer bilayer thin\nfilms with different thicknesses, named as XN film that N means the thickness of PA66\nfilm. The thickness of the aluminum foil substrate is 25 μm.”\n6. Line 292: The introduction of a series of environmental durability tests is too brief.\nSuggest providing specific testing conditions and testing time, rather than just\ndisplaying results before and after.\nResponse:\nThanks a lot for this comment. We provide the detailed environmental durability\ntest information in the section of Materials and Methods: 1) Low-temperature test: the\nsamples were put in a freezer with a constant temperature of -40 ℃ for one week. 2)\nHigh-temperature test: the samples were put on a heating stage with a constant\ntemperature of 80 ℃ for one week. 3) Acid test: the samples were immersed in sealed\nhydrochloric acid aqueous solution with pH=4 for one week. 4) Alkali test: the samples\nwere immersed in a sealed potassium hydroxide aqueous solution with pH=10 for one\nweek. 5) Water flushing test: the samples were fixed with a tilt angle of ~45 ° from the\nwater faucet with a water flow rate of 50 ml s-1. The water flowed over the samples into\nthe pool. The flushing process was 10 min. 6) UV exposure test: the samples were\nilluminated by a UV lamp (6 W) in a closed chamber for one week. 7) Wind test: the\nsamples were fixed on a glass in front of the fan with the gas flow of 83 cubic feet per\nminute (CFM) for one hour. The mass changes and spectral changes before and after\nthe experiments were recorded to evaluate the durability of the samples.\nTo further present the test process more intuitively, we have added illustrations for\nschematic in Fig. R3.\nFig. R3. MIR spectrums of X-films before and after environmental durability tests. (a)\nLow-temperature test. (b) High-temperature test. (c) acid test. (d) alkali test. (e) water\nflushing test. (f) UV exposure test. (g) wind test. The illustrations show the test device\nand process as schematic.\nThis is also the new Supplementary Fig. 22 in the revised manuscript (Page 31).\n7. X-films are prepared by electrospinning and are actually more like porous films\ncomposed of filamentous fabrics. Can the thickness alone fully characterize this film?\nAdditionally, can films of the same thickness prepared multiple times maintain\nconsistent film properties?\nResponse:\nMany thanks for this question. Under the same preparation parameters, the\nthickness alone can fully characterize this film, which is controlled by electrospinning\ntime. In this work, the influence factors such as solution concentration (1 g PA66: 2.5\nml formic acid: 2.5 ml acetic acid), voltage difference (25.5 kV), flow rate (0.1 ml hour-\n1), tip-to-collector distance (15 cm) and the rotation speed of the collector (80 rpm) are\nconstant, thus controlling fiber diameter of PA66 film at ~100 nm and making the air\nporosity of membrane about 83%. On this basis, the thickness of film becomes the\ndecisive factor in regulating the infrared performance. We also conducted the film\npreparation multiple times using the same conditions. As shown in Fig. R4, films of the\nsame thickness can maintain consistent film properties.\nFig. R4. The infrared properties of films with the same thickness prepared multiple\ntimes.\nResponse to Reviewer #2\nThis work presents a manufacturable approach to multispectral camouflage through\nroll-to-roll fabricated aluminum-PA66 bilayer films. The material demonstrates\ncompelling optical performance, balancing infrared stealth capabilities with radiative\ncooling functionality. The systematic experimental characterization provides evidence\nfor the film's dual-mode operation across critical wavelength bands. The proposed\ntechnology shows particular idea for applications requiring adaptive thermal\nmanagement and visual-infrared concealment.\nResponse:\nThanks very much to the Reviewer #2 for these insightful suggestions, which are\ncrucial to further improve the work. We are also delighted that the reviewer recognizes\nthat “The material demonstrates compelling optical performance… The proposed\ntechnology shows particular idea for applications requiring adaptive thermal\nmanagement and visual-infrared concealment.”. Below is our point-to-point response.\n1. The manuscript presents spectral trends for X-films with varying PA66 thicknesses.\nPlease include a consolidated summary table reporting for each thickness: (i) average\nemissivity in MWIR and LWIR bands, (ii) reflectance (or return signal strength) at 10.6\nμm, and (iii) average emissivity in the non-atmospheric windows (5–8 μm and 14–20\nμm). A recommended thickness range balancing camouflage and cooling performance\nshould also be provided.\nResponse:\nWe appreciate the reviewer for the constructive advice. A consolidated summary\ntable reporting infrared properties for each PA66 thickness of X-films is shown in Fig.\nR1.\nX-films ε ε R ε\nMWIR LWIR 10.6 μm NAW\nX15 4.0% 7.5% 93.4% 14.3%\nX30 7.0% 15.1% 86.4% 27.9%\nX45 10.3% 23.7% 77.6% 39.2%\nX60 13.0% 30.6% 69.6% 48.0%\nX75 19.3% 40.7% 59.4% 58.7%\nε : average emissivity in MWIR band; ε : average emissivity in LWIR band;\nMWIR LWIR\nR : reflectance at 10.6 μm; ε : average emissivity in the non-atmospheric\n10.6 μm NAW\nwindows (5–8 μm and 14–20 μm).\nTable R1. The infrared properties of X-films with varying PA66 thicknesses in different\nbands.\nThis is also the new Supplementary Table 3 in the revised manuscript (Page 40).\nAs described in the revised Supplementary Fig. 23-24 (see Fig. R1-2 for a\nscreenshot), we calculated the required emissivity of object for well-designed\ncamouflage in different environments with varying object temperature and background\nemissivity. It can be seen that in most simulated scenarios, the requirement on\nemissivity in both MWIR and LWIR of target object should be less than 0.6. Hence, X-\nfilms from X15 to X75 all can satisfy the camouflage demand. The radiative cooling\nperformance of X15 film may be a little lacking, so the recommended thickness range\nof PA66 film balancing camouflage and cooling performance is from 30 μm to 75 μm.\nCertainly, the average emissivity in LWIR band of X75 is just 0.4 (<0.6), and thus the\nthickness of X-films can still be slightly increased to enlarge radiative cooling\nperformance while maintaining infrared camouflage in specific scenario.\nFig. R1. A screenshot of the revised Supplementary Fig. 23 (Page 32).\nFig. R2. A screenshot of the revised Supplementary Fig. 24 (Page 33).\nTo clarify the recommended thickness range balancing camouflage and cooling\nperformance, we have revised the manuscript as follows:\nPage 15, Line 378\n“Additionally, the requirements on multispectral camouflage are changing for\nintegrating into the various environmental backgrounds (Supplementary Fig. 23-24\nand Supplementary Note 5). Thus, the X-films can be well-designed by adjusting the\nthickness of PA66 film, the mass ratio of loaded pigments, and the selection of PE film\nto achieve appropriate reflectivity or emissivity for better integrating into environments\n(Supplementary Fig. 25 and Supplementary Note 6). The recommended thickness range\nof PA66 film balancing camouflage and cooling performance is from 30 μm to 75 μm.”\n2. While the study demonstrates the feasibility of color customization, the side effects\nof pigment loading on mid-infrared performance are not quantitatively summarized.\nResponse:\nWe appreciate the reviewer’s comment. We are sorry that the quantitative\nsummarization on the side effects of pigment loading on mid-infrared performance are\nnot clearly presented. As shown in the revised Supplementary Note 6 and\nSupplementary Fig. 25 (see Fig. R3-4 for a screenshot), the relationship between the\ninfrared reflectivity of X-films and the mass ratio of loaded pigments is expressed to\nquantitatively summarize the optical influence of pigments. The slope represents the\ndegree of side effects. In MWIR band, the side effects of red/yellow/ blue pigments are\n-1.331/-2.584/-10.309 %/% respectively. And in LWIR band, the side effects of\nred/yellow/ blue pigments are -2.129/-7.991/-5.784 %/% respectively. Thus, it is\nimportant to control the mass ratio of loaded pigments to achieve appreciate reflectivity\nor emissivity for better integrating into environments.\nFig. R3. A screenshot of the revised Supplementary Note 6 (Page 9).\nFig. R4. A screenshot of the revised Supplementary Fig. 25 (Page 34).\nTo clarify the problem, we have revised the Supplementary Information as follows:\nPage 8, Line 204\n“The reflectivity of X-films is mainly influenced by three parts: the\nthickness of PA66 film ( ), the 𝑅𝑅m(a𝑡𝑡s,s𝜔𝜔 r,a𝛿𝛿t)io of loaded pigments ( ) and the selection of\nPE film ( ) (Supplementa𝑡𝑡ry Fig. 25). The relative functions can 𝜔𝜔be expressed as follows:\n𝛿𝛿\n100.239−0.243𝑡𝑡 𝑖𝑖𝑖𝑖 𝑀𝑀𝑀𝑀𝑀𝑀𝑅𝑅\n𝑅𝑅(𝑡𝑡) = \n101.088−0.547𝑡𝑡 𝑖𝑖𝑖𝑖 𝐿𝐿𝑀𝑀𝑀𝑀𝑅𝑅\n93.416−1.331𝜔𝜔𝑟𝑟𝑟𝑟𝑟𝑟 𝑖𝑖𝑖𝑖 𝑀𝑀𝑀𝑀𝑀𝑀𝑅𝑅\n𝑅𝑅(𝜔𝜔𝑟𝑟𝑟𝑟𝑟𝑟) = \n86.856−2.129𝜔𝜔𝑟𝑟𝑟𝑟𝑟𝑟 𝑖𝑖𝑖𝑖 𝐿𝐿𝑀𝑀𝑀𝑀𝑅𝑅\n93.380−2.584𝜔𝜔𝑦𝑦𝑟𝑟𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 𝑖𝑖𝑖𝑖 𝑀𝑀𝑀𝑀𝑀𝑀𝑅𝑅\n𝑅𝑅𝜔𝜔𝑦𝑦𝑟𝑟𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 = \n84.354−7.991𝜔𝜔𝑦𝑦𝑟𝑟𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦 𝑖𝑖𝑖𝑖 𝐿𝐿𝑀𝑀𝑀𝑀𝑅𝑅\n90.811−10.309𝜔𝜔𝑏𝑏𝑦𝑦𝑏𝑏𝑟𝑟 𝑖𝑖𝑖𝑖 𝑀𝑀𝑀𝑀𝑀𝑀𝑅𝑅\n𝑅𝑅(𝜔𝜔𝑏𝑏𝑦𝑦𝑏𝑏𝑟𝑟) = \n84.090−5.784𝜔𝜔𝑏𝑏𝑦𝑦𝑏𝑏𝑟𝑟 𝑖𝑖𝑖𝑖 𝐿𝐿𝑀𝑀𝑀𝑀𝑅𝑅\n0.834 𝑖𝑖𝑖𝑖 𝑏𝑏𝑏𝑏𝑡𝑡ℎ 𝑀𝑀𝑀𝑀𝑀𝑀𝑅𝑅 𝑎𝑎𝑖𝑖𝑎𝑎 𝐿𝐿𝑀𝑀𝑀𝑀𝑅𝑅 𝑤𝑤𝑖𝑖𝑡𝑡ℎ 𝑃𝑃𝑃𝑃\nwhere the slope𝛿𝛿 r(e𝑃𝑃p𝑃𝑃re)s=ents the side effects on mid-infrared performance.”\n1 𝑖𝑖𝑖𝑖 𝑏𝑏𝑏𝑏𝑡𝑡ℎ 𝑀𝑀𝑀𝑀𝑀𝑀𝑅𝑅 𝑎𝑎𝑖𝑖𝑎𝑎 𝐿𝐿𝑀𝑀𝑀𝑀𝑅𝑅 𝑤𝑤𝑖𝑖𝑡𝑡ℎ𝑏𝑏𝑜𝑜𝑡𝑡 𝑃𝑃𝑃𝑃\n3. The “plicated aluminum foil” substrate is credited with enhancing laser camouflage\nvia scattering, but no quantitative surface morphology (e.g., roughness, wrinkle\nwavelength/amplitude) is provided.\nResponse:\nThanks a lot for this constructive comment. Due to the randomness of the plicated\naluminum foil, we have selected a representative location and captured the optical\nphotograph and scanning electron microscopy image of the cross-section of the plicated\naluminum foil (Fig. R5). It can be seen that the wrinkle amplitude of the plicated\naluminum is within the range of 0.2 to 1 mm while the wrinkle wavelength is within\nthe range of 2 to 10 mm. The microscopic roughness of pure aluminum surface is\napproximately at the level of several hundred nanometers as shown in Fig. R6.\nFig. R5. The cross-section morphology of the plicated aluminum foil. (a) Optical\nphotograph of the plicated aluminum foil. (b) Scanning electron microscopy image of\nthe plicated aluminum foil. It is a representative location for reference because the\nsurface morphology of the plicated aluminum foil is random.\nThis is also the new Supplementary Fig. 16 in the revised manuscript (Page 25).\nFig. R6. Surface profile map of pure aluminum foil (Scan size is 10 μm).\n4. In Fig. 1e caption, symbols “√” and “×” are mentioned but not present in the figure.\nResponse:\nWe apologize for our mistake and thank the reviewer very much for this reminder.\nWe have revised “√” and “×” into “Yes” and “No” in Fig. 1e caption to make it uniform.\n5. The citation for Supplementary Fig. 14 appears to refer to Supplementary Fig. 15. A\nthorough proofreading is needed.\nResponse:\nThanks a lot for this kinder reminder. We have carefully checked the citation for\nSupplementary Fig. 14 (Supplementary Fig. 13 in the revised manuscript) and\nSupplementary Fig. 15 (Supplementary Fig. 14 in the revised manuscript), which are\nright in the manuscript. Supplementary Fig. 14 exhibits infrared photographs in LWIR\noutdoors to show the outstanding stealth effects and the camouflage trend with the\nthickness of PA66 film. Supplementary Fig. 15 demonstrates the temperature measured\noutdoors for ambient air, bare control and the cases with X-films to show excellent\ncooling capacity. Thus, the citations are corresponding to the text and we express our\ngratitude to the reviewer for the reminder again.\n6. Mie scattering theory requires strict assumptions regarding wavelength and particle\nsize. Given the fiber diameter (~100 nm) and MIR wavelengths (3–20 μm), the\napplicability of Mie theory is questionable. The authors should justify its use or employ\na more suitable model to support the claim that scattering is negligible in the MIR\nregime.\nResponse:\nWe appreciate the reviewer’s comment. Mie solution is the exact analytical\nsolution of Maxwell's equations for a spherical particle or an infinite long cylinder (this\nwork), which is rigorously valid for all sizes [1-5]. Specifically, Rayleigh scattering is\nthe small-size approximation of Mie scattering when the object size is much smaller\nthan the wavelength. Hence, the scattering efficiency shown in Fig. 2c is the exact result\nwithout any assumption or approximation. Evidently, when a fiber with a small\ndiameter is used (~100 nm), the scattering efficiency is negligible in the long\nwavelength like MIR.\n[1] H. C. Hulst, H. C. van de Hulst, Light scattering by small particles. (Courier\nCorporation, 1981).\n[2] C. F. Bohren, R. H. Donald, Absorption and scattering of light by small particles.\n(John Wiley & Sons, 2008).\n[3] J. Schaefer, S. C. Lee, A. Kienle, Calculation of the near fields for the scattering of\nelectromagnetic waves by multiple infinite cylinders at perpendicular incidence. J.\nQuant. Spectrosc. Ra. 113, 2113-2123 (2012).\n[4] K. Klier, Absorption and scattering in plane parallel turbid media. J. Opt. Soc. Am.\n62, 882-885 (1972).\n[5] https://www.oceanopticsbook.info/view/theory-electromagnetism/level-2/mie-\ntheory-overview\n7. The bio-inspired aspect is underdeveloped and appears disconnected from the main\ntechnical content. The term “bio-inspired” appears in the title, but the Introduction does\nnot adequately motivate this perspective, and the link to insect cocoons feels tenuous.\nResponse:\nThanks very much for this comment and we apologize for the fuzziness of the bio-\ninspired aspect which appears disconnected from the main technical content and has\ntenuous link to insect cocoons. Hence, to avoid this problem, we have deleted\ncorresponding description about bio-inspired aspect and revised text in the manuscript.\nPage 1, Line 1\n“Hierarchical design and scalable production of radiative cooling film featuring\nmultispectral camouflage”\nPage 2, Line 28\n“Here, we demonstrate an aluminum-PA66 metal organic bi-layer thin film through\nhierarchical design at both the molecular and microscale levels and scalable\nproduction, enabling camouflage in infrared (3-5 μm and 8-14 μm) and laser (10.6\nμm) bands with efficient radiative cooling in the non-atmospheric window (5-8 μm\nand 14-20 μm).”\nPage 5, Line 107\n“Hierarchical design\nThe randomly stacked structure always exhibits no optical orientation in a specific\ndirection, thus contributing to uniform color like white or dark in appearance such as\nnanofiber membranes or porous coatings 49. It is not only suitable for visible band, but\nalso creates possibilities for an infrared performance scheme with weak angle\ndependence. However, current materials are usually highly emissive in the mid-\ninfrared band, not satisfying the requirements on multispectral camouflage above.\nHence, to achieve low emissivity in MWIR and LWIR with weak angle dependence (Fig.\n1b), it is vital to seek elaborate molecular-level design on appropriate material.”\n8. The manuscript states that laser camouflage at 10.6 μm results from both PA66\nabsorption and substrate scattering. More detailed discussion is expected.\nResponse:\nWe appreciate the reviewer for this comment. The laser camouflage is related to\nthe received back signal in the laser detector, thus influenced by sample absorption and\nsubstrate scattering. As shown in Fig. R7a and Fig. R8a, a sample with no absorption\nand scattering can enable the optical power meter (detector) to receive the signals of all\nthe emitted light from quantum cascade lasers (emitter). If possessing absorption at 10.6\nμm, the sample will partially reduce the light intensity by absorption and weaken the\nreceived signal strength in optical power meter (Fig. R7b). Similarly, plicated substrate\nwill cause the incident light to scatter in all directions deviating from the light path that\nenters the detector, thereby reducing the received signal (Fig. R8b). Based on these two\nfactors, the X-films exhibit excellent laser camouflage potential.\nFig. R7. The laser camouflage effect influenced by sample absorption. (a) Optical path\ntransmission schematic of the sample with no absorption. (b) Optical path transmission\nschematic of the sample with absorption. It is clear that the sample with absorption at\n10.6 μm will partially reduce the light intensity and weaken signal strength received by\noptical power meter.\nThis is also the new Supplementary Fig. 17 in the revised manuscript (Page 26).\nFig. R8. The laser camouflage effect influenced by sample scattering. (a) Optical path\ntransmission schematic of the sample with no scattering. (b) Optical path transmission\nschematic of the sample with scattering. It is clear that plicated substrate will cause the\nincident light to scatter in all directions deviating from the original light path that enters\nthe detector, thereby reducing the received signal.\nThis is also the new Supplementary Fig. 18 in the revised manuscript (Page 27).\nTo clarify the influence of PA66 absorption and substrate scattering on laser\ncamouflage at 10.6 μm, we have revised the manuscript as follows:\nPage 12, Line 289\n“Samples with PA66 spun on the smooth aluminum plates and on the plicated aluminum\nfoils were used to clarify the influences on laser camouflage by the absorbance of the\nPA66 layer and the Geometric scattering effect of substrates at 10.6 μm, respectively\n(Supplementary Fig. 16). As shown by optical path transmission schematic in\nSupplementary Fig. 17-18, the sample with absorption or scattering effect both can\nweaken the received signal strength in the optical power meter. The detailed results\nillustrated that the reflection strength of the back signal of X-films with different\nthicknesses of PA66 films on the plicated aluminum foils decreased rapidly compared\nto bare aluminum foils under the combined action of absorption and scattering, which\nall exhibited excellent laser camouflage potential (Fig. 3h).”\n9. The method of bonding between the PA66 layer and the aluminum substrate is not\nclearly described. The interfacial adhesion and long-term stability of the bilayer\nstructure under mechanical stress or thermal cycling should be discussed.\nResponse:\nThanks a lot for the constructive comment. The bond between the PA66 layer and\nthe aluminum substrate is regarded as intermolecular forces such as van der Waals force\n[1]. The electrospinning process could also incorporate electrostatic adhesion to the\ninterface between polymer fibers and substrate matrix [2]. Finally, the interfacial\nadhesion of the bilayer structure is 128 mN measured by universal testing machine\n(Instron 3366). To further improve the performance on interfacial adhesion, it can be\nachieved by substrate modification such as adding the chain entanglements on the\ninterface or precursor solution modification such as introducing chemical adhesive\ntogether with thermal treatment [3-4]. However, these methods should ensure that\nadded materials have negligible impact on mid-infrared properties. Then, we have\ntested the long-term stability of the bilayer structure under mechanical stress. It can be\nseen that the mechanical strength and optical performance remain almost no change\nafter the bending test (Fig. R9). Additionally, we have measured the infrared spectra of\nX-films before and after thermal cycling, also verifying the excellent long-term stability\nof the bilayer structure (Fig. R10).\nFig. R9. Bending test of the X-film. (a) A schematic of the test. The sample is bent and\nstraightened repeatedly for 100 times. (b) Stress-strain curves of the sample before and\nafter the bending test. (c) Infrared spectra of the sample before and after the bending\ntest. They together prove that the bilayer structure of the sample has excellent long-\nterm stability under mechanical stress.\nThis is also the new Supplementary Fig. 20 in the revised manuscript (Page 29).\nFig. R10. Thermal cycling test of the X-film. The sample undergoes five temperature\ncycles between -40 ℃ and 80 ℃ over a period of five days. It verifies that the bilayer\nstructure of the sample has excellent long-term stability under thermal cycling.\nThis is also the new Supplementary Fig. 21 in the revised manuscript (Page 30).\n[1] A. Baji, L. Zhou, Y. Mai, Z. Yang, H. Yao, On the Adhesion performance of a single\nelectrospun fiber. Appl. Phys. A 118, 51-56 (2015).\n[2] C. H. Lee, A. Khalina, S. H. Lee, Importance of interfacial adhesion condition on\ncharacterization of plant-fiber-reinforced polymer composites: a review. Polymers 13,\n438 (2021).\n[3] Q. Shi et al., Effect of Surface Interactions on Adhesion of Electrospun Meshes on\nSubstrates. Langmuir 30, 13549-13555 (2014).\n[4] G. Animi, A. A. Gharehaghaji, Improving adhesion of electrospun nanofiber mats\nto supporting substrate by using adhesive bonding. Int. J. Adhes. Adhes. 86, 40-44\n(2018).\n10. The study acknowledges a trade-off between MIR camouflage and radiative cooling\nperformance depending on PA66 thickness. However, the manuscript does not\nsufficiently address how this trade-off limits simultaneous optimization. The research\ngap regarding materials that truly combine both functions without compromise is not\nfully resolved by this work.\nResponse:\nWe thank the reviewer very much for this helpful suggestion. The tradeoff between\nMIR camouflage and radiative cooling performance can be further gained by adding\ninorganic particles to combine both functions without compromise. Take the red\npigment α-Fe O for example, we have sprayed particles with the same mass on X-films\n2 3\nwith different PA66 thickness. It can be seen the radiative cooling performance of X-\nfilms can be promoted greatly although the PA66 thickness is thin, especially in the\nband from 14 to 20 μm (Fig. R11). Thus, when increasing the thickness of PA66 film,\nthe radiative cooling performance can remain excellent while the MIR camouflage\npotential will be adjusted with variable emissivity. Consequently, by selecting different\npigments that have infrared properties of high emissivity in non-atmospheric window\nand low-emissivity in atmospheric window, the research gap that truly combine both\nfunctions without compromise may be fully resolved.\nFig. R11. The infrared spectra of X-films with different PA66 thicknesses by spraying\nthe same mass of α-Fe O .\n2 3\n11. The claim that “the heat dissipation capacity of X-films was correlated negatively\nwith the thickness of PA66 film” is misleading. Both experimental and spectral data\nshow that thicker PA66 layers lead to higher emissivity in the non-atmospheric\nwindows, which should enhance radiative cooling.\nResponse:\nWe are very sorry for this mistake and thank the reviewer for this kind reminder.\nWe have revised the corresponding description in the manuscript.\nPage 10, Line 247\n“Contrary to the relation between camouflage performance and the thickness of PA66\nfilm, the heat dissipation capacity of X-films was correlated positively with the thickness\nof PA66 film, where it existed a balance.”\nResponse to Reviewer #3\nThis paper presents a composite film material for camouflage purpose with radiative\ncooling performance. The context is clear and the logic is smooth. Due to current\ntechnical issues in the manuscript, I suggest revision.\nResponse:\nWe thank the Reviewer #3 very much for the constructive report, which is very\nimportant for us to further improve the quality of this manuscript. We are also delighted\nthat the reviewer recognizes that “The context is clear and the logic is smooth”. Below\nis our point-to-point response to the professional comments.\n1. The proposed film is “an aluminum-PA66 metal organic bi-layer thin film”. “Metal”\nis a noun and thus is not properly used here. Please consider another way to describe\nthe composite film.\nResponse:\nWe appreciate the reviewer’s comment. To describe the composite film more\nclearly, we have revised “an aluminum-PA66 metal organic bi-layer thin film” into “an\naluminum-PA66 metal-based polymer bilayer thin film” in the manuscript.\n2. Line 66 states that metals/semiconductors with low emittance have poor heat\ndissipation, which is not accurate. They have poor radiation loss but can dissipate heat\nby their high thermal conductivity. Please elaborate or correct the statement.\nResponse:\nThanks very much for this kind reminder. To clarify this problem, we have revised\nthe statement in the manuscript as follows.\nPage 3, Line 67\n“Infrared stealth fabrics have also been studied with several representative strategies\nlike reducing the infrared emissivity or the temperature of the surface. The infrared\noptical performance regulation often relies on materials like metals, semiconductors\nand MXenes with broadband low emittance, while surface temperature can be\ncontrolled by thermal insulation material like aerogel and hollow structure 22-24.\nHowever, these two methods will both cause thermal discomfort in the human body due\nto their poor heat dissipation in radiative and conductive capacity, respectively.”\n3. Fig 1e caption: there is no √ or × in the figure.\nResponse:\nWe are very sorry for our mistake and thank the reviewer for this kind reminder.\nWe have revised “√” and “×” into “Yes” and “No” in Fig. 1e caption to make it uniform.\n4. Line 131-132, please provide evidence or reference.\nResponse:\nThanks a lot for this comment. Take polyamide 6 as example, it has two common\ncrystal structures (α-phase and γ-phase) with differences in the molecular chain\narrangements, conformations, and intermolecular interactions [1, 2]. Then, to explore\nthe relationship between these differences and bond vibrations in the IR region, it has\nbeen researched by the work [Nat. Commun. 16, 2009 (2025)] in both simulation and\nexperiment results [3]. As shown in Fig. R1 (a screenshot of the cited literature), the\nabsorption peaks and intensity of PA6 in two phases exist distinct differences on\nsimulated vibrational spectra (Fig. R1f and Fig. R1g), thus exhibiting high IR\ntransmission by stable fabrication in γ-phase while low IR transmission by drop-casting\nprocess mostly in α-phase (Fig. R1i). Thus, to provide evidence on the claim “The MIR\nspectrum of polymers is also affected by the absorption peak from crystallization or\nhydrogen bond interaction in the fabrication process”, we have cited these works in the\nrevised manuscript (Ref. 57-59 in Page 5).\nFig. R1. A screenshot of the cited literature [3]. (d, e) The crystal structure of α-phase\nand γ-phase of PA6. (f, g) Simulated vibrational spectra of α-phase (f) and γ-phase (g)\nin the IR region. The molecular bond vibrational intensity in the α-phase is much higher\nthan that of the γ-phase. (h) A schematic diagram of the high drawing process, and this\neffect results in the high orientation of molecular chains for the changes of chain\nconformations and crystal structures. (i) Total transmission of infrared and visible light\nfor two processes resulting in α-phase and γ-phase.\n[1] D. Holmes, C. Bunn, D. Smith, The crystal structure of polycaproamide: nylon 6. J.\nPolym. Sci. 17, 159-177 (1955).\n[2] R. Seguela, Overview and critical survey of polyamide6 structural habits:\nmisconceptions and controversies. J. Polym. Sci. 58, 2971-3003 (2020).\n[3] Z. Chen et al., An infrared-transparent textile with high drawing processed Nylon 6\nnanofibers. Nat. Commun. 16, 2009 (2025).\n5. Please provide data on mechanical properties and/or mechanical durability.\nResponse:\nWe appreciate the reviewer’s comment. We have tested mechanical properties of\nX-films by universal testing machine (Instron 5944) (Fig. R2). Then, the mechanical\ndurability is verified and it can be seen that the mechanical strength and optical\nperformance remain almost no change after the bending test (Fig. R3).\nFig. R2. Stress-strain curves of the X-films with different PA66 thicknesses.\nThis is also the new Supplementary Fig. 19 in the revised manuscript (Page 28).\nFig. R3. Bending test of the X-film. (a) A schematic of the test. The sample is bent and\nstraightened repeatedly for 100 times. (b) Stress-strain curves of the sample before and\nafter the bending test. (c) Infrared spectra of the sample before and after the bending\ntest. They together prove that the bilayer structure of the sample has excellent long-\nterm stability under mechanical stress.\nThis is also the new Supplementary Fig. 20 in the revised manuscript (Page 29).\n6. Please provide performance comparison with existing literature in terms of\ncamouflage and cooling performance.\nResponse:\nThanks a lot for this kind reminder. We have compared the performance of our\nwork with existing literature in terms of camouflage and cooling performance as\nfollows:\nReference Structure C C C P\nVis MIR Laser Cooling\nOur work Metal-based polymer √ √ √ √\nbilayer thin film\n[1] Composite fabric √\n[2] Composite fabric √\n[3] Composite fabric √\n[4] Meta-surface √ √\n[5] Meta-surface √ √\n[6] Meta-surface √ √ √\n[7] Meta-surface √ √\n[8] Photonic crystal √ √\n[9] Photonic crystal √ √ √\n[10] Photonic crystal √ √\n[11] Photonic crystal √ √ √\n[12] Photonic crystal √ √ √\n[13] Photonic crystal √ √ √\n[14] Photonic crystal √ √ √ √\n[15] Photonic crystal √ √ √\n[16] Photonic crystal and √ √\nmeta-surface\n[17] Photonic crystal and √ √\nmeta-surface\n[18] Photonic crystal and √ √ √ √\nmeta-surface\n[19] Photonic crystal and √ √\nmeta-surface\n[20] Photonic crystal and √ √ √ √\nmeta-surface\n[21] Photonic crystal and √ √ √\nmeta-surface\n[22] Photonic crystal and √ √\nnano-mesh pattern\n*C : Visible camouflage performance; C : Mid-infared camouflage performance;\nVis MIR\nC\nLaser\n: Laser camouflage performance; P\nCooling\n: Cooling performance; “√” means that\nthe structure has corresponding property.\nTable R1. The performance comparison with existing literature in terms of camouflage\nand cooling performance.\nThis is also the new Supplementary Table 1 in the revised manuscript (Page 36).\n[1] Y. Zhang et al., A waste textiles-based multilayer composite fabric with superior\nelectromagnetic shielding, infrared stealth and flame retardance for military\napplications. Chem. Eng. J. 471, 144679 (2023).\n[2] H. Ma et al., Double-sided functional infrared camouflage flexible composite fabric\nfor thermal management. Ceram. Int. 49, 16422-16432 (2023).\n[3] G. Cui et al., Freestanding graphene fabric film for flexible infrared camouflage.\nAdv. Sci. 9, 2105004 (2022).\n[4] S. Fang et al., Self-assembled skin-like metamaterials for dual-band camouflage.\nSci. Adv. 10, eadl1896 (2024).\n[5] Z. Lin et al., Flexible meta-tape with wide gamut, low lightness and low infrared\nemissivity for visible-infrared camouflage. Adv. Mater. 36, 2410336 (2024).\n[6] Q. Kang, D. Li, W. Wang, K. Guo, Z. Guo, Multiband tunable thermal camouflage\ncompatible with laser camouflage based on GST plasmonic metamaterial. J. Phys. D:\nAppl. Phys. 55, 065103 (2022).\n[7] X. Feng et al., Large-area low-cost multiscale-hierarchical metasurfaces for\nmultispectral compatible camouflage of dual-band lasers, infrared and microwave. Adv.\nFunct. Mater. 32, 2205547 (2022).\n[8] X. Huang et al., Engineered spectrally selective and spatially segmented emittances\nfor infrared camouflage textiles. J. Mater. Chem. C 12, 6240 (2024).\n[9] W. Xi et al., Ultrahigh-efficient material informatics inverse design of thermal\nmetamaterials for visible-infrared-compatible camouflage. Nat. Commun. 14, 4694\n(2023).\n[10] H. Zhu et al., High-temperature infrared camouflage with efficient thermal\nmanagement. Light-Sci. Appl. 9, 60 (2020).\n[11] L. Huang et al., Multiband camouflage design with thermal management.\nPhotonics Res. 11, 839-851 (2023).\n[12] Q. Kang, K. Guo, Z. Guo., A tunable infrared emitter based on phase-changing\nmaterial GST for visible-infrared compatible camouflage with thermal management.\nPhys. Chem. Chem. Phys. 25, 27668 (2023).\n[13] B. Qin, Y. Zhu, Y. Zhuo, M. Qiu, Q. Li, Whole-infrared-band camouflage with\ndual-band radiative heat dissipation. Light-Sci. Appl. 12, 246 (2023).\n[14] H. Zhu et al., Multispectral camouflage for infrared, visible, lasers and microwave\nwith radiative cooling. Nat. Commun. 12, 1805 (2021).\n[15] X. Jiang et al., Implementing of infrared camouflage with thermal management\nbased on inverse design and hierarchical metamaterial. Nanophotonics 12, 1891-1902\n(2023).\n[16] J. Huang et al., Large-area and flexible plasmonic metasurface for laser–infrared\ncompatible camouflage. Laser Photonics Rev. 17, 2200616 (2023).\n[17] J. Kim, C. Park, J. W. Hahn, Metal–semiconductor–metal metasurface for\nmultiband infrared stealth technology using camouflage color pattern in visible range.\nAdv. Opt. Mater. 10, 2101930 (2022).\n[18] M. Pan et al., Multi-band middle-infrared-compatible camouflage with thermal\nmanagement via simple photonic structures. Nano Energy 69, 104449 (2020).\n[19] J. S. Lim et al., Multiresonant selective emitter with enhanced thermal\nmanagement for infrared camouflage. Appl. Mater. Inter. 16, 15416-15425 (2024).\n[20] X. Li et al., Multispectral camouflage nanostructure design based on a particle\nswarm optimization algorithm for color camouflage, infrared camouflage, laser stealth,\nand heat dissipation. Opt. Express 31, 44811-44822 (2023).\n[21] M. Luo et al., Tunable infrared detection, radiative cooling and infrared-laser\ncompatible camouflage based on a multifunctional nanostructure with phase-change\nmaterial. Nanomaterials 12, 2261 (2022).\n[22] H. K. Woo et al., Visibly transparent and infrared reflective coatings for personal\nthermal management and thermal camouflage. Adv. Funct. Mater. 32, 2201432 (2022).\n7. I notice some improper expressions. Please go through the manuscript to avoid such\ntypos or mistakes.\n• Typo in line 21: “human activity” should be “human activities”.\n• Line 26: “these designs based on top-down one-dimensional photonic crystals or\nmeta-surfaces always require”. Please check grammar.\n• Line 31: “camouflage on … bands”. “On” should be “in”.\n• Line 59: “just as animals disguise themselves to evade predators”. Please check\ngrammar.\n• Line 61, the objects should be plural.\nResponse:\nWe appreciate these kind reminders. The corresponding revisions are as follows:\n1) Page 2, Line 21\n“Various outdoor scenarios from human activities to equipment operations demand\nboth temperature control and self-protection from environment, which are often\ncontradictory from the optical perspective.”\n2) Page 2, Line 26\n“However, these methods on the basis of one-dimensional photonic crystals or meta-\nsurfaces always rely on complex design and stringent fabrication process, and result\nin strong angular dependence.”\n3) Page 2, Line 28\n“Here, we demonstrate an aluminum-PA66 metal-based polymer bilayer thin film\nthrough hierarchical design at both the molecular and microscale levels and scalable\nproduction, enabling camouflage in infrared (3-5 μm and 8-14 μm) and laser (10.6\nμm) bands with efficient radiative cooling in the non-atmospheric window (5-8 μm\nand 14-20 μm).”\n4) Page 3, Line 46\n“Both of them are crucial in modern society that cooling technology is beneficial amidst\nthe escalating impacts of global warming and rising peak daytime temperatures 1-2\nwhile camouflage provides protection, just as animals disguise themselves against\npredators 3-7.”\n5) Page 3, Line 64\n“Especially for objects between 30 ℃ and 100 ℃ such as human bodies 17,18, electronic\nequipment 19, base stations 20, and tent camps 21, they can be easily detected as primary\ntargets due to their elevated temperature and emissivity different from the background,\nas dictated by Stefan-Boltzmann law.”\n8. In the introduction, the authors mention “temperature comfort” as a main purpose\nhere, but only cooling performance is presented. No heating comfort in a cold\nenvironment is involved. Please justify this point or revise the context. Also, the authors\nshould elaborate in the first paragraph on why the two purposes are important and why\nthey contradict each other.\nResponse:\nWe thank the reviewer for this comment and apology for the misleading. We have\nrevised “temperature comfort” into “cooling comfort” in the manuscript. Then, to\nelaborate why cooling and camouflage purposes are important and why they contradict\neach other, we have also revised the statement as follow:\nPage 3, Line 44\n“Under various outdoor scenarios, appearance or optical properties of objects (human,\nanimals, facility, etc) often need to serve two major purposes, cooling comfort and self-\nprotection from environment, at the same time. Both of them are crucial in modern\nsociety that cooling technology is beneficial amidst the escalating impacts of global\nwarming and rising peak daytime temperatures 1-2 while camouflage provides\nprotection, just as animals disguise themselves against predators 3-7. However, these\ntwo requirements are often contradictory, as they share similar bandwidth.\nAs a typical example, radiative cooling and infrared camouflage both cover mid-\ninfrared band (2.5-20 μm) but require different optical properties. To achieve excellent\ncooling performance, radiative cooling materials efficiently emit heat into the outer\nspace (~3 K) through the atmospheric transparency window (3-5 μm and 8-14 μm) and\nexchange heat with the ambient (~298 K) through the non-atmospheric transparency\nwindow (5-8 μm and 14-20 μm) by infrared thermal radiation. Recently, radiative\ncoolers have been widely used in various fields such as fabric 8, building 9,10, glacier\nconservation 11, and electronic equipment 12. For personal thermal management,\nradiative cooling textiles have gradually moved from research to practical research,\nwith advanced structures including hierarchical fiber membrane 13, bump textured\nstructure 14, particle distributed system 15 and photon-engineered optical properties like\nbroadband or selective emitters 16. However, high infrared radiation in the atmospheric\ntransparency window of materials indicates distinct signal in thermal imagers, which\nis not beneficial to infrared camouflage. Especially for objects between 30 ℃ and 100 ℃\nsuch as human bodies 17,18, electronic equipment 19, base stations 20, and tent camps 21,\nthey can be easily detected as primary targets due to their elevated temperature and\nemissivity different from the background, as dictated by Stefan-Boltzmann law. Infrared\nstealth fabrics have also been studied with several representative strategies like\nreducing the infrared emissivity or the temperature of the surface. The infrared optical\nperformance regulation often relies on materials like metals, semiconductors and\nMXenes with broadband low emittance, while surface temperature can be controlled\nby thermal insulation material like aerogel and hollow structure 22-24. However, these\ntwo methods will both cause thermal discomfort in the human body due to their poor\nheat dissipation in radiative and conductive capacity, respectively. Therefore, it is\nessential to develop camouflage materials that not only suppress infrared signatures\nbut also maintain radiative cooling performance in the non-detection window.”\n9. What is the mechanism that PA66 is a perfect fit here rather than nylon 6, nylon 11,\nand nylon 12. Please explain and elaborate.\nResponse:\nThanks a lot for this comment. The MIR spectrum of polymers is affected by the\nabsorption peak from crystallization or hydrogen bond interaction in the fabrication\nprocess. Take polyamide 6 as example, it has two crystal structures (α-phase and γ-\nphase) with differences in the molecular chain arrangements, conformations, and\nintermolecular interactions [1-3]. The α-phase which is the most common and stable\ncrystal phase possesses the molecular chains fully unfolding in a straight chain\nconformation and arranging in an antiparallel manner. In comparison, in the case of γ-\nphase, the amid groups are rotated and no longer coplanar to the carbon chains, and the\nchains are arranged in a parallel manner to form hydrogen bonds. These two phases\nexhibit different absorption peaks in FTIR spectra (Fig. R4). Then, we have statistically\nanalyzed and measured the infrared spectra of PA6, PA66, PA11 and PA12 by both\nreferences and experiment results (Fig. R5) [4-7]. The crystalline peak of PA6 is at 930\ncm-1 and 960 cm-1. The crystalline peak of PA66 is at 935 cm-1. The crystalline peak of\nPA11 is at 582 cm-1, 628 cm-1 and 688 cm-1. The crystalline peak of PA12 is at 580 cm-\n1, 626 cm-1 and 681 cm-1. Hence, in simultaneous consideration of laser camouflage at\n10.6 μm (~ 943 cm-1), PA66, which has crystalline peak at 935 cm-1 that are more\nclosely to 10.6 μm in comparison with other polyamides like PA6, PA11 and PA12,\npresents the most desirable absorption band close to the selective MIR spectrum in Fig.\n1a.\nFig. R4. A screenshot of the cited literature [3]. (d, e) The crystal structure of α-phase\nand γ-phase of PA6. (f, g) Simulated vibrational spectra of α-phase (f) and γ-phase (g)\nin the IR region. The molecular bond vibrational intensity in the α-phase is much higher\nthan that of the γ-phase. (h) A schematic diagram of the high drawing process, and this\neffect results in the high orientation of molecular chains for the changes of chain\nconformations and crystal structures. (i) Total transmission of infrared and visible light\nfor two processes resulting in α-phase and γ-phase.\nFig. R5. FTIR spectra of PA6, PA66, PA11 and PA12. The crystalline peak of PA6 is at\n930 cm-1 and 960 cm-1. The crystalline peak of PA66 is at 935 cm-1. The crystalline\npeak of PA11 is at 582 cm-1, 628 cm-1 and 688 cm-1. The crystalline peak of PA12 is at\n580 cm-1, 626 cm-1 and 681 cm-1. The crystalline peak of PA66 is closer to the laser\nband (10.6 μm).\nThis is also the new Supplementary Fig. 1 in the revised manuscript (Page 10).\n[1] D. Holmes, C. Bunn, D. Smith, The crystal structure of polycaproamide: nylon 6. J.\nPolym. Sci. 17, 159-177 (1955).\n[2] R. Seguela, Overview and critical survey of polyamide6 structural habits:\nmisconceptions and controversies. J. Polym. Sci. 58, 2971-3003 (2020).\n[3] Z. Chen et al., An infrared-transparent textile with high drawing processed Nylon 6\nnanofibers. Nat. Commun. 16, 2009 (2025).\n[4] Y. Ma, T. Zhou, G. Su, Y. Li, A. Zhang, Understanding the crystallization behavior\nof polyamide 6/polyamide 66 alloys from the perspective of hydrogen bonds: projection\nmoving-window 2D correlation FTIR spectroscopy and the enthalpy. RSC Adv. 6,\n87405-87415 (2016).\n[5] G. Zhang, Y. Li, D. Yan, Polymorphism in nylon-11/montmorillonite nanocomposite.\nJ. Polym. Sci. Pt. B-Polym. Phys. 42, 253-259 (2004).\n[6] N. Ma et al., Crystal transition and thermal behavior of Nylon 12. e-Polymers 20,\n346-352 (2020).\n[7] N. Vasanthan, D. Salem, Infrared spectroscopic characterization of oriented\npolyamide 66: band assignment and crystallinity measurement. J. Polym. Sci. Pt. B-\nPolym. Phys. 38, 516-524 (2000).\n10. For Fig 2i, a CIE color space plot should be better.\nResponse:\nWe appreciate the reviewer’s comment. The CIE color space plot is drawn\naccording to the visible spectrum of X-films with three primary colors (Fig. R6), which\nis better to describe the color intuitively.\nFig. R6. A CIE color space plot of X-films with three primary colors.\nThis is also the new Fig. 2i in the revised manuscript (Page 9).\nResponse to Reviewer #4\nThis work reports a PA66 electrospinning nanofiber film combined with aluminum foil\nto realize a camouflage membrane. The design leverages the infrared optical properties\nof nylon66, achieving the desired high reflectance in the 3–5 μm and 8–14 μm\natmospheric windows while maintaining strong absorption in other thermal infrared\nbands, thus offering a low-cost stealth solution. Moreover, the absorption peak of nylon\n66 at 10.6 μm—though relatively weak and of questionable effectiveness—may impart\nsome capability for laser detection stealth. It should be noted that the core material,\nelectrospinning nylon nanofibers, has previously been reported in the Nature\nCommunications (doi.org/10.1038/s41467-025-57366-9) for radiative cooling textiles,\nwith quite similar material properties. This study, however, nicely repurposes those\nsame infrared optical characteristics for stealth applications and investigates them in\ndetail. However, the idea of camouflaging and radiatively cooling hot objects by\nemission in the 5-8 and > 13 μm is a well known idea, with several papers detailing this\nconcept reported in the literature. Therefore, from both a material and conceptual\nstandpoint, the work appears to have limited novelty. Furthermore, the cooling ability\nof this design is likely limited because of its emittance outside the window. On the\nscalability front, this is a nice advance, but perhaps more suited for a more discipline\nspecific journal. Specific comments on the manuscript are as follows:\nResponse:\nWe appreciate the Reviewer #4 very much for the great efforts on this manuscript\nand we are delighted that the reviewer recognizes that “… nicely repurposes those same\ninfrared optical characteristics for stealth applications and investigates them in\ndetail… On the scalability front, this is a nice advance”. The problem on core material\n(electrospinning nylon nanofibers) is clarified in detail in Question #1 in terms of\nmaterial screening mechanism, specific material category and performance pursuit\nindicator. Additionally, the problem on the concept of multispectral camouflage and\nradiative cooling is illustrated in detail in Question #2 in material system, scalability\nand angle dependence compared to previous works. Below, we present our point-by-\npoint responses to all the constructive comments and suggestions.\n1. Nylon fibers as a longwave transmissive but otherwise thermally emissive material\nhas been previously discussed by others.1,2 So materially, this is not very new, even\nthough the authors detail the properties of nylon. This was discussed as early as 2015.\nResponse:\nThanks very much for this constructive comment. Here we would like to clarify\nthat the material in our work is carefully selected and well designed in terms of material\nscreening mechanism, specific material category and performance pursuit indicator\ncompared to previous works although nylon fibers have been discussed as a longwave\ntransmissive but otherwise thermally emissive material. The detailed innovations of our\nmaterial are demonstrated as follows:\n1) Material screening mechanism\nThe material screening method is new for polymer-based complex spectral design,\nwhich are focused on functional groups rather than single chemical bond. Previous\nworks usually analyze the effect of few bond vibrations on mid-infrared absorption\nperformance using enumeration method and then introduce suitable material directly,\nwhich lacks universal screening principle and process. The functional groups are the\nfoundation classification of organics and can systematically represent some basic\nproperties of polymers in comparison with chemical bonds. Here, in our work, we hope\nthat the research on functional groups for material screening in mid-infrared\nperformance will propose a universal spectral design strategy for polymers and opens\nup tremendous opportunities for polymer based photonic devices. When treating\nfunctional group as a whole, it can not only alleviate the influence of the chemical bond\nby other bonds, but also more intuitively display the effect on mid-infrared spectrum\nby different types of polymers. Meanwhile, this new functional group screening method\ncan be suitable to many fields such as selective radiative cooling (ether) [1],\nnon-selective radiative cooling (halohydrocarbon, carboxylic acid, ester) [2],\ninfrared-transparent textile (alkyl, amide, nitrile) [3-5] or future diverse applications other than\nmultispectral infrared camouflage.\nFurthermore, nylon fibers used in previous works [4, 6] are mainly focused on the\nband from 8 to 14 μm, which is near the peak of human body thermal radiation. The\nthermal emissive performance in other bands is ignored and not mentioned although it\nis an inherent property of the material. Our work pay attention to multispectral\nselectivity within a wider band, thus utilizing the whole infrared property of nylon\nmaterial. In fact, polymer composed of carbonyl (polyketone) may be also an\nappropriate candidate as shown in Fig. 1e (see Fig. R1 for a screenshot) but less\ncommon than nylon. Thus, we choose nylon, which is widely available and used in\ndaily life, as the raw material.\nFig. R1. A screenshot of the revised Fig. 1e (Page 6).\n2) Specific material category\nAlthough nylon material has been proposed and used in personal thermal\nmanagement, it is a broad category and has many branches. In our work, the\nrequirements on multispectral camouflage include high absorbance at 10.6 μm for laser\ncamouflage to interfere with the laser detector receiving a back signal. Thus, we further\nstudy the absorption peak from crystallization or hydrogen bond interaction between\ndifferent nylon materials and finally ensure that PA66 which has crystalline peak at 935\ncm-1 that are more closely to 10.6 μm in comparison with other polyamides like PA6,\nPA11 and PA12 is more desirable material. Additionally, we contrast the spectra of PA6\nand PA66 fibrous membranes with similar emissivity in LWIR as shown in Fig. R2.\nIt can be seen that PA66 also has better radiative cooling performance in the non-\natmospheric window (5-8 μm and 14-20 μm) than PA6. Therefore, we choose PA66 as\nexperimental subject rather than other nylon materials.\nFig. R2. The comparison on mid-infrared spectra of PA66 and PA6 fibrous membranes\nwith similar emissivity in LWIR. The transmission spectrum data of PA6 fibrous\nmembrane is from the literature [Nat. Commun. 16, 2009 (2025)][4].\n3) Performance pursuit indicator\nThe angle dependence of nylon fibrous membrane has not been proposed and\nresearched in the previous works. Here, we think the randomly stacked structure\nexhibits no optical orientation in a specific direction and thus may contribute to weak\nangle dependence. Then, both optical simulation and field tests are conducted to verify\nour opinion (Fig. R3). It can be seen that PA66 fibrous membrane indeed possesses\nweak angle dependence, which is significant for practical applications since the\nobservation angle of infrared camera varies greatly in the processing of moving.\nFig. R3. Simulation and experimental results to verify the weak angle dependence of\nPA66 fibrous membrane. (a) A screenshot of the revised Fig. 2e (Page 9). (b) A\nscreenshot of the revised Fig. 2f (Page 9). (c) A screenshot of the revised Fig. 3f (Page\n12). (d) A screenshot of the revised Fig. 4e (Page 16).\nIn conclusion, we think PA66 is used in our work with careful selection and\nelaborate design in terms of material screening mechanism, specific material category\nand performance pursuit indicator in comparison with previous works. However, there\nis no doubt that previous works have brought us much inspiration and we have cited\nrelevant literatures in the revised manuscript (Ref. 56-57 in Page 5).\n[1] D. Li et al., Scalable and hierarchically designed polymer film as a selective thermal\nemitter for high-performance all-day radiative cooling. Nat. Nanotechnol. 16, 153-158\n(2021).\n[2] S. Son, Y. Liu, D. Chae, H. Lee, Cross-linked porous polymeric coating without a\nmetal-reflective layer for sub-ambient radiative cooling. ACS Appl. Mater. Interfaces\n12, 57832-57839 (2020).\n[3] P. Hsu et al., Radiative human body cooling by nanoporous polyethylene textile.\nScience 353, 1019-1023 (2016).\n[4] Z. Chen et al., An infrared-transparent textile with high drawing processed Nylon 6\nnanofibers. Nat. Commun. 16, 2009 (2025).\n[5] H. Kim, S. McScherry, B. Brown, A. Lenert, Selectively enhancing solar scattering\nfor direct radiative cooling through control of polymer nanofiber morphology. ACS\nAppl. Mater. Interfaces 12, 43553-43559 (2020).\n[6] J. K. Tong et al., Infrared-transparent visible-opaque fabrics for wearable personal\nthermal management. ACS Photonics 2, 769-778 (2015).\n2. The idea of combining radiative cooling with camouflage has been quite well\nexplored. See, for example, H Zhu et. al., Nat Comm, 12(1), 2021. Deng et. al, Adv.\nFunc. Mat., 2500122, 2025, and Wang et. al., Opt Mat Express, 13(10), 2023. The\nauthors’ material is likely more scalable than some of the previously deployed designs,\nand potentially better for humans. But the concept is known.\nResponse:\nWe appreciate the reviewer’s comment. Here we would like to clarify that our\nwork has quite difference and improvement in material system, scalability and angle\ndependence compared to previous works although the concept of combining radiative\ncooling with camouflage has been proposed and there are some research works in recent\nyears.\nPrevious works always rely on photonic crystals or meta-surfaces, which require\nstringent top-down fabrication processes with nanometer precision. Thus, the cost on\nraw materials (such as germanium) and fabrication process (such as physical vapor\ndeposition) is high and the scalability is limited to achieve large-area preparation.\nWe hope to enhance the large-scale process by using low-cost and easily available polymers\nso that the camouflage technology with radiative cooling will further move towards\napplication.\nAdditionally, photonic crystals or meta-surfaces generally exhibit strong angle\ndependence due to their periodic structure or resonant cavity. We have designed a one-\ndimensional photonic crystal with the combination of the\nGe/ZnS/Ge/ZnS/Ge/ZnS/Ge/ZnS/Ge/Silica substrate which meets the requirements on\nmultispectral camouflage with radiative cooling (Fig. R4). It can be seen that this\ndesigned photonic crystal has strong angle dependence especially at 10.6 μm against\nlaser detection. In our work, the randomly stacked structure of polymer fibrous\nmembrane provides new solution for weak angle dependence, which is also verified\neffective in both simulation and experiments.\nFig. R4. The possible problem on angle dependence of one-dimensional photonic\ncrystals. (a) Schematic of a designed one-dimensional photonic crystal structure for\nmultispectral camouflage with radiative cooling. (b) The mid-infrared spectrum of the\ndesigned one-dimensional photonic crystal at the incident angle of 0°. (c, d) The mid-\ninfrared spectrum of the designed one-dimensional photonic crystal at the incident\nangle of 0° and 50° in the transverse electric (TE) mode and transverse magnetic (TM)\nmode, respectively.\nFinally, just as the history of research on daytime radiative cooling materials, the\nconcept was introduced by Prof. Fan by one-dimensional photonic crystal [1] and then\nmany works based on polymers were studied for better performance and scalability [2-\n5]. By now, radiative cooling technology has moved towards practical use and brought\nsome commercial products. Therefore, we hope that our work can also advance\npractical solutions for multispectral camouflage with radiative cooling by a scalable\nand low-cost polymer film, then inspiring more creative ideas to promote this field.\n[1] A. P. Raman, M. A. Anoma, L. Zhu, E. Rephaeli, S. Fan, Passive radiative cooling\nbelow ambient air temperature under direct sunlight. Nature 515, 540-544 (2014).\n[2] Y. Zhai et al., Scalable-manufactured randomized glass-polymer hybrid\nmetamaterial for daytime radiative cooling. Science 355, 1062-1066 (2017).\n[3] J. Mandal et al., Hierarchically porous polymer coatings for highly efficient passive\ndaytime radiative cooling. Science 362, 315-319 (2018).\n[4] D. Li et al., Scalable and hierarchically designed polymer film as a selective thermal\nemitter for high-performance all-day radiative cooling. Nat. Nanotechnol. 16, 153-158\n(2021).\n[5] R. Wu et al., Spectrally engineered textile for radiative cooling against urban heat\nislands. Science 384, 1203-1212 (2024).\n3. For humans, is radiative cooling outside the LWIR window practical? Previous works\nhave shown that outside the window, humans gain rather than lose heat.3 Indeed for\nvertical surfaces, it seems that it is better to have the opposite spectral profile of what\nthe authors suggest.4 Thus, the cooling ability of the design seems to be limited.\nResponse:\nThanks a lot for this comment. The radiative cooling performance outside the\nLWIR window is also practical and effective and it is not in conflict with the opinion in\nthese works [1,2]. The aforementioned works are mainly aimed at extremely hot\nenvironments like summer daytime or thermal localized scenes like heat island cities,\nwhere the ambient temperature is higher than human body and it is necessary to isolate\nthe external energy input from non-atmospheric window. However, in actual situations,\nthere is a significant portion of the year when the environmental temperature is lower\nthan the human body temperature such as spring, autumn and nighttime. Under these\ncircumstances, the ambient temperature is lower than human body temperature and the\nradiative cooling performance outside the LWIR window will become more\npronounced. Therefore, the cooling ability of the design is not limited and is practical\nin human body.\n[1] R. Wu et al., Spectrally engineered textile for radiative cooling against urban heat\nislands. Science 384, 1203-1212 (2024).\n[2] F. Xie et al., Subambient daytime radiative cooling of vertical surfaces. Science 386,\n788-794 (2024).\n4. Frankly, the use of “Bio-inspired” in the title seems somewhat overstated. Although\nthe design is described as inspired by cocoons, cocoons do not function by reflecting\ninfrared radiation for camouflage, so the connection in terms of functionality or material\ndesign is weak.\nResponse:\nThanks very much for this comment and we apologize for the fuzziness of the bio-\ninspired aspect which the connection between material and cocoons in terms of\nfunctionality or material design is weak. Hence, to avoid this problem, we have deleted\ncorresponding description about bio-inspired aspect and revised text in the manuscript.\nPage 1, Line 1\n“Hierarchical design and scalable production of radiative cooling film featuring\nmultispectral camouflage”\nPage 2, Line 28\n“Here, we demonstrate an aluminum-PA66 metal organic bi-layer thin film through\nhierarchical design at both the molecular and microscale levels and scalable\nproduction, enabling camouflage in infrared (3-5 μm and 8-14 μm) and laser (10.6\nμm) bands with efficient radiative cooling in the non-atmospheric window (5-8 μm\nand 14-20 μm).”\nPage 5, Line 107\n“Hierarchical design\nThe randomly stacked structure always exhibits no optical orientation in a specific\ndirection, thus contributing to uniform color like white or dark in appearance such as\nnanofiber membranes or porous coatings 49. It is not only suitable for visible band, but\nalso creates possibilities for an infrared performance scheme with weak angle\ndependence. However, current materials are usually highly emissive in the mid-\ninfrared band, not satisfying the requirements on multispectral camouflage above.\nHence, to achieve low emissivity in MWIR and LWIR with weak angle dependence (Fig.\n1b), it is vital to seek elaborate molecular-level design on appropriate material.”\n5. While electrospinning can indeed be scaled to roll-to-roll production, the manuscript\ndoes not actually demonstrate any roll-to-roll process. It may be advisable to reconsider\nhow this is framed in the title.\nResponse:\nThanks a lot for this comment and we are very sorry for this mistake. We have\ntaken the photograph of laboratorial electrospinning equipment which is a simplified\nroll-to-roll production device (Fig. R5). Certainly, it does not reach the scale of\nindustrialization. Thus, to avoid the misunderstanding, we have revised “roll-to-roll”\ninto “scalable” in the title.\nPage 1, Line 1\n“Hierarchical design and scalable production of radiative cooling film featuring\nmultispectral camouflage”\nFig. R5. The photograph of laboratorial electrospinning process.\n6. The work does not present any solar reflection data. Since aluminum absorbs to some\nextent in the UV–visible range and has low thermal emissivity, it tends to heat up under\nsunlight. If the nylon fiber layer can scatter solar radiation and significantly reduce\nabsorption by the aluminum foil, this would be highly beneficial for practical\ntemperature control under solar exposure. Based on only the modest thermal emittance\nin the non-atmospheric window, the cooling effect in the outdoor may not be so\n‘efficient’ as claimed in the Abstract.\nResponse:\nWe appreciate the reviewer’s insightful suggestion. As the reviewer predicted,\nthe nylon fiber can scatter solar radiation by Mie theory and significantly reduce absorption\nby the aluminum foil, thus exhibiting high reflectivity in solar band. The reflection\nspectra of X45 and X72 films are shown in Fig. R6a and they can all effectively prevent\nthe thermal input of sunlight to suppress temperature rise. During the field temperature\ntest in the daytime, the cases using the same device as that used at night with X45 and\nX72 films were 7 ℃ and 11 ℃ cooler than the case with X0 film, showing excellent\ncooling performance (Fig. R6b). Thus, it is also highly beneficial for practical\ntemperature control under solar exposure. However, the detection in nighttime is also\nimportant other than daytime, where the high emissivity in the non-atmospheric\nwindow will become pivotal especially in the objects with high temperature. In this\nsituation, the effects on temperature control have the same tendency as the description\nin the manuscript.\nFig. R6. The solar spectra and temperature measured outdoors for X-films. (a) The\nreflection spectrum of X45 and X72 films in solar band. (b) The temperature\ncomparison among X0, X45 and X72 films in the daytime.\nThis is also the new Supplementary Fig. 15 in the revised manuscript (Page 24).\nOnce again, we would like to express our gratitude to the reviewer for the kind\nreminder. To clarify practical temperature control of X-films under solar exposure, we\nhave revised the manuscript as follows:\nPage 11, Line 265\n“In the temperature test, the cases with X30, X45, X62, and X72 film were 5 ℃, 9 ℃,\n10 ℃, and 12 ℃ cooler than the case with X0 film, respectively, showing excellent\ncooling capacity as well (Supplementary Fig. 14). Then, we further assessed the\ntemperature control of X-films under solar exposure. The nylon fiber can scatter solar\nradiation by Mie theory, thus exhibiting high reflectivity in solar band (Supplementary\nFig. 15). During the field temperature test in the daytime, the cases with X45 and X72\nfilms were 7 ℃ and 11 ℃ cooler than the case with X0 film, maintaining superior\ncooling performance. All the results consistently demonstrate the splendid properties\nof X-films, further illustrating the importance of material selection on PA66.”\n7. Camouflage by reflection is tricky, because the reflected temperature has to be the\nsame as the background temperature. Given that the average diameter of the nylon\nfibers is only 0.1 μm, one can infer that they are transmissive in the longwave IR, i.g.\nreflection by the underlying Al is primarily specular. For example, in Fig. 4f, the cold\ninfrared signal observed at the shoulder may originate from reflection of the sky’s\nthermal radiation. But does it not stand out from the warm background, defeating the\nvery point of the design? This is a potential issue worth discussing. Surface treatments\nof the aluminum foil could perhaps mitigate this problem.\nResponse:\nWe thank the reviewer very much for this helpful reminder and we apology for\nthis mistake. As the reviewer clarified, the reflection of Al substrate is primarily\nspecular, perhaps introducing the thermal radiation reflection of the environment such\nas sky which has cold infrared signal. This problem can be solved by regionalized\ncustomized design through the thickness of nylon fibrous membrane and the load mass\nof pigment particles, just as described in Supplementary Fig. 23-24 (see Fig. R7-8 for\na screenshot). To avoid the visual problem in Fig. 4f, we have increased the thickness\nof PA66 film and the mass ratio of green pigments for the sample at the shoulder to\nenlarge its infrared emissivity so that the sample will reduce the reflection of the sky’s\nthermal radiation. Then, we have taken the infrared and optical images of a human\nwearing garments made of three different textiles on a cloudy day anew (Fig. R9).\nThe images have the same tendency with that previously stated but regionalized well-\ndesigned X-fabric exhibit uniform color with the background in the infrared image.\nAdditionally, surface treatments of the aluminum foil may also mitigate the problem on\nthe thermal radiation reflection of the sky. The literature has proposed an infrared\ncamouflage device on the Lambertian surface composed of aluminum film and\npolyimide substrate which exhibits low emissivity (~0.1), low specular reflectance\n(~0,05) over 0.75-25 μm [1]. The field tests show that the Lambertian surface can\nreduce the peak value of the target-background contrast both indoors and outdoors\ncompared to the low-emissivity smooth surface (Fig. R10). This work has inspired us\nthat we can reduce the impact of the thermal radiation from the sky by the surface\ntreatments of the aluminum foil to transform a smooth surface into the Lambertian\nsurface.\nFig. R7. A screenshot of the revised Supplementary Fig. 23 (Page 32).\nFig. R8. A screenshot of the revised Supplementary Fig. 24 (Page 33).\nFig. R9. Infrared and optical photographs of a human wearing vests consisting of white\ncotton fabric, green cotton fabric, and the regionalized well-designed green X-fabric.\nThis is also the new Fig. 4f in the revised manuscript (Page 16).\nFig. R10. A screenshot of the cited literature [1]. (a) Schematic representation of the\nexperimental setup. The target object surface is divided into two parts (blue and yellow).\nThe blue part is covered with I) the low-e smooth surface or II) the low-e Lambertian\nsurface to test the camouflage performance. The yellow part is covered with a\nblackbody (III) to show the real temperature of the target surface. A hot object is stuck\nonto the top of a toy car and passes by the target object. An infrared camera is set aside\nfor monitoring. (b) Indoor experimental results. (c) Outdoor experimental results. Five\ncaptured frames (i–v) are presented in each case, for both the low-e Lambertian surface\nand the low-e smooth surface.\n[1] Y. Huang et al., Infrared camouflage utilizing ultrathin flexible large-scale high-\ntemperature-tolerant Lambertian surfaces. Laser Photonics Rev. 15, 2000391 (2021).\nTo clarify this problem, we have revised the manuscript and corresponding figure\nas follows:\nPage 15, Line 370\n“The X-fabric was also well-designed by body region with different color and emissivity\nagainst various actual scenarios like shrubberies. Fig. 4f presented the infrared and\noptical images of a human wearing garments made of three different textiles on a\ncloudy day. The images showed that although the green cotton fabric exhibited a\nsimilar color to the shrubberies in comparison with the white cotton fabric, it still could\nnot achieve infrared camouflage due to its high emissivity as the same as the white\ncotton fabric. However, the regionalized well-designed green X-fabric displayed a\nsimilar color to the background in both infrared and optical photographs.”\nPage 17, Line 401\n“(f) Infrared and optical photographs of a human wearing vests consisting of white\ncotton fabric, green cotton fabric, and the regionalized well-designed green X-fabric.\nThe X-fabric can achieve both visible and infrared camouflage against the background\nof shrubberies. Scale bar: 20 cm.”\n8. There seems to be a clear tradeoff between LWIR camouflage and laser reflection at\n10.6 μm. Can the design proposed by the authors simultaneously do both well? That\nseems a somewhat doubtful.\nResponse:\nWe appreciate the reviewer’s comment and understand the concern about the\ntradeoff between LWIR camouflage and laser reflection at 10.6 μm. These two parts are\nindeed contradictory because they are both within the band range of the LWIR.\nHowever, infrared detection by thermal imagers relies on the average emissivity from\n8 to 14 μm while the laser detection depends on the received back signal at a single\nband of 10.6 μm. Thus, if the absorption width of material at 10.6 μm is narrow enough,\nit will have negligible impact on the average emissivity in LWIR, which means infrared\ncamouflage and laser camouflage are compatible. In our work, the LWIR emissivity is\nobtained by weighted averaging of the infrared spectra of materials and the spectral\nirradiance of a blackbody in 8 to 14 μm band that includes the 10.6 μm band as shown\nin Supplementary Note 3 and Supplementary Fig. 2 (see Fig. R11-12 for a screenshot).\nCombining the results on laser camouflage potential in Fig. 3f (see Fig. R13 for a\nscreenshot), it is verified that the infrared camouflage and laser camouflage can be\nsimultaneously achieved in the actual experiments. For further improvement, it is\nbeneficial to enhance the absorption strength and reduce the bandwidth of materials at\n10.6 μm so that the performance on both infrared camouflage and laser camouflage will\nbe better.\nFig. R11. A screenshot of the revised Supplementary Note 3 (Page 6).\nFig. R12. A screenshot of the revised Supplementary Fig. 2 (Page 11).\nFig. R13. A screenshot of the revised Fig. 3f (Page 13).\n9. Does thermal camouflage and laser camouflage collectively qualify as multispectral\ncamouflage? The first is multispectral for their design, and the second actually occurs\nwithin the LWIR. So line 275 of their manuscript should be edited accordingly.\nResponse:\nWe thank very much for the reviewer’s kind reminder and we are sorry for this\nmisunderstanding. To clarify more clearly, we have edited the corresponding text as\nfollows:\nPage 11, Line 283\n“Having verified the infrared camouflage and radiative cooling capacity of X-films, it\nis important to evaluate the other requirements such as laser camouflage.”\n10. Is is not more likely for technologies like LIDAR (cheaper light sources and\ndetectors) to be used to detect humans rather than 10.6 μm lasers (LWIR reflective\ncamouflage gear seems a relatively unused concept)? If yes, then would this textile not\nbe counterproductive?\nResponse:\nWe appreciate the reviewer’s constructive comment. LIDAR with cheap light\nsources and detectors proposed by the reviewer is a good technology that the main\noperating wavelength band is concentrated at 1.06 μm. However, it has some\ndisadvantages such as significant damage to human eyes, poor atmospheric\ntransmission performance and limited antijamming capability. The laser detector at 10.6\nμm can alleviate these problems and work in coordination with the thermal imaging\nsystem. The technology in our work is mainly focused on the scenarios as a universal\nsolution with the working temperature from 30 to 100 ℃ such as human bodies,\nelectronic equipment, building external walls and vehicle surfaces while textile is used\nas a representative exhibition. Thus, we aim at camouflage against 10.6 μm carbon\ndioxide laser which is mature in practical application. If camouflage against 1.06 μm\nlaser detection is required, our design should be optimized due to the negligible\nabsorption performance of X-films in solar band. Here, we can introduce MXene films\nwhich have high absorptivity in solar band and low emissivity in mid-infrared band to\nreplace aluminum substrate [1], then adjust fabrication process of PA66 on MXene\nfilms such as spraying and blade coating to decrease the scattering impact by nanofibers.\nThe envisioned device above may achieve multispectral camouflage consistent with the\nmanuscript while including 1.06 μm laser stealth.\n[1] Z. Yang et al., Optically selective catalyst design with minimized thermal emission\nfor facilitating photothermal catalysis. Nat. Commun. 15, 7599 (2024).\n1. Tong, J. K. et al. Infrared-Transparent Visible-Opaque Fabrics for Wearable Personal\nThermal Management. ACS Photonics 2, 769–778 (2015).\n2. Chen, Z. et al. An infrared-transparent textile with high drawing processed Nylon 6\nnanofibers. Nat Commun 16, 2009 (2025).\n3. Wu, R. et al. Spectrally engineered textile for radiative cooling against urban heat\nislands. Science 384, 1203–1212 (2024).\n4. Xie, F. et al. Subambient daytime radiative cooling of vertical surfaces. Science 386,\n788–794 (2024).\nResponse to Reviewer #5\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports.\nThis is part of the Nature Communications initiative to facilitate training in peer review\nand to provide appropriate recognition for Early Career Researchers who co-review\nmanuscripts.\nResponse:\nThanks very much to the Reviewer #5 for co-reviewing this manuscript and\nproviding insightful suggestions, which are helpful to further improve the work."}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors responded well to all the questions and doubts. The manuscript is ready for publication.", "reviewer_2": "All the comments have been well addressed. The work can be considered for publication.", "reviewer_3": "My comments are mostly addressed except for one remaining issue. For the mechanical and thermal durability tests, performing only 100 bending cycles or 5 days of thermal cycling does not justify the claim of “excellent long-term stability.” The authors should refer to relevant durability testing standards and avoid overstating the performance. Furthermore, because the film is intended for outdoor camouflage applications, incorporating scratch and abrasion resistance tests would provide a more comprehensive evaluation of its durability.", "reviewer_4": "The authors have addressed many of the questions that we had raised. While we commend them for their efforts, we are unfortunately not convinced that the work represents a level of novelty suitable for publication in Nature Communications. The most notable aspect, scalability, is perhaps better suited for a more specialized journal (e.g. a journal that focuses on thermal sensing). On this point, we would defer to the editor’s view.\nSome specific points are given below:\n1. The points of novelty claimed – screening polymers based on functional groups, and angular characterizations, are hardly novel. In other contexts, including radiative cooling, these have been explored many times. It seems that the authors are straining themselves to find points of novelty here. The choice of PA66 offers a tangible advancement, but is it really a breakthrough? In fact, the authors have not sufficiently addressed the question on the tradeoff between 10.6 μm reflection and LWIR camouflage. Please see below.\n2. The authors’ response to the question of the tradeoff between laser reflection and LWIR camouflage is misleading. The authors claim: “infrared detection by thermal imagers relies on the average emissivity from 8 to 14 μm while the laser detection depends on the received back signal at a single band of 10.6 μm. Thus, if the absorption width of material at 10.6 μm is narrow enough, it will have negligible impact on the average emissivity in LWIR, which means infrared camouflage and laser camouflage are compatible.”\nBut Fig. 2D of their manuscript clearly shows that for absorptance at 10.6 μm to be significant (> 0.5), the entire LWIR reflectance must drop. Their defence, based on narrow and broad ranges, has nothing to do with the evidence they present. This is concerning to see. In fact, if the laser absorption were to be even higher, LWIR emissivity may rise to as low as 0.5.\n3. The authors response to the question of whether the textile is suitable for cooling human beings is not well supported. The authors claim: “The aforementioned works are mainly aimed at extremely hot environments like summer daytime or thermal localized scenes like heat island cities, where the ambient temperature is higher than human body and it is necessary to isolate the external energy.” Neither of these are true. For example, net heating can occur at moderately hot environments even when emitters radiate to the sky. https://www.sciencedirect.com/science/article/pii/S2666386424003345. For their design, its going to be much worse, as radiation to the window is minimized. The authors also compare the cooling performance of their design to bare aluminium, which is a strange baseline to be using for a wearable.\n4. In response to remark 7 about camouflage via reflection being tricky, the authors note that “This problem can be solved by regionalized customized design through the thickness of nylon fibrous membrane and the load mass of pigment particles” but would that not change the emissivity? Isn’t a better solution to just make the underlying aluminium rough? The information in Supplementary Figs. 23 and 24 is not clear.\n5. Related to #4, the authors’ work and the controls they use encouraged us to look at IR camouflage uniforms. It seems Ghillie suits, which are loose fitting and thus closer to ambient temperature due to convection rather than temperature of the object to be camouflaged, are quite good at thermal camouflaging. Existing thermally camouflaged variants of these designs may already do the job quite well. It may be worthwhile to compare such designs (e.g.\nhttps://blog.beezcombatsystems.com/predator-ghillie-spectralflage.html) against the design proposed by the authors. That would be better than using aluminium as a control.", "reviewer_5": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Response to Reviewer #3\nWe thank the Reviewer #3 very much for the great efforts on this manuscript and\nwe are delighted that the reviewer recognizes “My comments are mostly addressed\nexcept for one remaining issue”. Below is our detailed response to the remaining\nconcern.\nTo avoid overstating the long-term performance, we have deleted relevant\ndescription and experimental results in the revised manuscript. Then, we have tested\nthe scratch resistance performance of XNP films (X-films by polyethylene film\nencapsulation on the surface) by standard pencil test, which indicates that XNP films\ncan withstand the hardness of “B” under a weight of 500 g (Fig. R1). For the abrasion\ntest, a glass with the XNP film attached is placed upside down on the sandpaper (grit\nsize 400) (Fig. R2a). A 100 g weight is placed on the surface of the glass. The glass is\nmoved around a 10 cm square as one cycle (from position 1 to 2 to 3 to 4 and then back\nto position 1). The infrared spectra and visual appearance are almost unchanged after\nthe abrasion test with 10 cycles, verifying its excellent durability (Fig. R2b).\nFig. R1. Photograph of XNP film after a standard pencil test. The XNP film can\nwithstand the hardness of “B” under a weight of 500 g.\nThis is also the new Supplementary Fig. 22 in the revised manuscript (Page 31).\nFig. R2. Abrasion test for the XNP film. (a) Schematic of the test method. (b)\nComparison on the infrared spectra before and after the abrasion test. The illustration\nshows the visual appearance of the XNP film before and after the abrasion test. The\ninfrared spectra and visual appearance are almost unchanged after the abrasion test with\n10 cycles.\nThis is also the new Supplementary Fig. 23 in the revised manuscript (Page 32).\nTo clarify this problem, we have revised the manuscript as follows:\nPage 12, Line 300\n“Durability is also an important problem in practical applications. X-films have good\nmechanical properties under mechanical stress (Supplementary Fig. 19-20). For\nfurther optimization, we increased the stability of X-films by polyethylene (PE) film\nencapsulation on the surface, named as XNP film (N means the thickness of PA66 film).\nFig. 3i demonstrated that the curve shapes of MIR spectra were similar between XNP\nfilm and XN film because polyethylene showed high mid-infrared transmission which\nhas only C-C and C-H bonds. Then, a series of tests were conducted to verify the\nenvironmental durability, including low-temperature tests, high-temperature tests, acid\ntests, alkali tests, water flushing tests, UV exposure tests, and wind tests. The mass\nchanges were less than 1.0% after each of these seven tests, indicating the films were\nwell preserved (Fig. 3j). Additionally, the reflection in LWIR also remained nearly\nunchanged so that the MIR property of XNP films would work for a long time (Fig. 3k\nand Supplementary Fig. 21). The scratch and abrasion resistance test also verified that\nthe XNP film possessed good durability (Supplementary Fig. 22-23). These satisfactory\nresults all illustrate that the durability of XNP films has been increased, which is\nexpected to stand up to practical use.”\nPage 20, Line 487\n“7) Wind test: the samples were fixed on a glass in front of the fan with the gas flow of\n83 cubic feet per minute (CFM) for one hour. The mass changes and spectral changes\nbefore and after the experiments above were recorded to evaluate the durability of the\nsamples. 8) Scratch resistance test: sharpened pencils with different hardness levels\nwere pushed on the sample’s surface to create a scratch over 1 cm in length at a 45°\nangle. The test was conducted until a pencil ruptured the coating, which meant the\nhardest pencil that did not cause rupture was recorded as the hardness level of the\ncoating. The load weight was 500 g during the test. 9) Abrasion resistance test: a glass\nwith the sample attached was placed upside down on the sandpaper (grit size 400). A\n100 g weight was placed on the surface of the glass. The glass was moved around a 10\ncm square as one cycle (from position 1 to 2 to 3 to 4 and then back to position 1). The\ninfrared spectra and visual appearance were recorded before and after the test.”\nResponse to Reviewer #4\nWe very appreciate the Reviewer #4 for evaluating our manuscript and offering us\nmany constructive suggestions and we are delighted that the reviewer recognizes that\n“The authors have addressed many of the questions that we had raised”. Below, we\npresent our detailed point-by-point responses to the remaining important concerns.\n1. The points of novelty claimed – screening polymers based on functional groups, and\nangular characterizations, are hardly novel. In other contexts, including radiative\ncooling, these have been explored many times. It seems that the authors are straining\nthemselves to find points of novelty here. The choice of PA66 offers a tangible\nadvancement, but is it really a breakthrough? In fact, the authors have not sufficiently\naddressed the question on the tradeoff between 10.6 μm reflection and LWIR\ncamouflage. Please see below.\nResponse:\nWe thank the reviewer for this constructive comment. Here we would like to\nclarify the differences between previous works and our work in detail and hope that the\ncorresponding misunderstanding may be alleviated.\nPrevious works, including radiative cooling, generally propose suitable material\ndirectly by analyzing the effect of few bond vibrations on mid-infrared absorption or\nbriefly mentioning the concept of functional groups [1-4]. For example, in the work\n[Nat. Nanotechnol. 16, 153-158 (2021)], it has just enumerated the bond vibrations such\nas –CHO (2810-2710 cm-1), C=C (1880-1785 cm-1), C=O (1825-1725 cm-1), C–S (650-\n600 cm-1), S–S (<500 cm-1), C–O–C (1260-1110 cm-1), C–OH (1239-1030 cm-1), –CF\n3\n(1148 cm-1), Si–O–Si (1110 cm-1) and then ensured polyethylene oxide as the desirable\nselective thermal emitter. Thus, there lacks a universal screening principle and process\nfor polymers to achieve ideal mid-infrared spectrum. Here, in our work, we have\nsystematically researched and summarized the common functional groups, which are\nbasic unit of polymers and possess representative significance on the effects on mid-\ninfrared spectrum, and expected this strategy will open up tremendous opportunities for\npolymer based photonic devices not only in the field of multispectral camouflage.\nCertainly, it also agrees well with the results on material selection in above references.\nThen, current works in radiative cooling focus more on the angle dependence in\nterms of the average emissivity from 2.5-20 μm or 8-13 μm. In our work, we concern\nabout not only the average emissivity, but also specific wavelength such as 10.6 μm,\nespecially the position change of absorption peak with angles. Therefore, we choose\nthe randomly stacked structure in fibrous membrane that exhibits no optical orientation\nin a specific direction and thus contributes to weak angle dependence, which is verified\neffective by both optical simulation and field tests.\nWe hope that our response may clarify the above concerns more clearly and the\nquestion the reviewer raised on the tradeoff between 10.6 μm reflection and LWIR\ncamouflage is discussed in detail as below.\n[1] D. Li et al., Scalable and hierarchically designed polymer film as a selective thermal\nemitter for high-performance all-day radiative cooling. Nat. Nanotechnol. 16, 153-158\n(2021).\n[2] X. Wu et al., A dual-selective thermal emitter with enhanced subambient radiative\ncooling performance. Nat. Commun. 15, 815 (2024).\n[3] A. Aili et al., Selection of polymers with functional groups for daytime radiative\ncooling. Mater. Today Phys. 10, 100127 (2019).\n[4] T. Li et al., A radiative cooling structural material. Science 364, 760-763 (2019).\n2. The authors’ response to the question of the tradeoff between laser reflection and\nLWIR camouflage is misleading. The authors claim: “infrared detection by thermal\nimagers relies on the average emissivity from 8 to 14 μm while the laser detection\ndepends on the received back signal at a single band of 10.6 μm. Thus, if the absorption\nwidth of material at 10.6 μm is narrow enough, it will have negligible impact on the\naverage emissivity in LWIR, which means infrared camouflage and laser camouflage\nare compatible.”\nBut Fig. 2D of their manuscript clearly shows that for absorptance at 10.6 μm to be\nsignificant (> 0.5), the entire LWIR reflectance must drop. Their defence, based on\nnarrow and broad ranges, has nothing to do with the evidence they present. This is\nconcerning to see. In fact, if the laser absorption were to be even higher, LWIR\nemissivity may rise to as low as 0.5.\nResponse:\nWe appreciate the reviewer’s comment and apology for the misleading on our\nresponse. In Fig. 2D, the increase on absorption at 10.6 μm is caused by the thickening\nPA66 film, thus resulting in the decrease on LWIR reflectance. Taking this aspect into\naccount, we select the plicated aluminum foil as substrate to reduce the back signal at\n10.6 μm and achieve laser camouflage while remaining low average LWIR emissivity.\nAs shown in Fig. 3g-h (see Fig. R1 for a screenshot), with the absorbance of the PA66\nlayer and the Geometric scattering effect of the plicated aluminum foil, all X-films with\ndifferent thicknesses will satisfy the received back signal at 10.6 μm less than 0.5 and\nexhibit better laser camouflage potential, where scattering plays a dominant role at low\nthickness and absorption takes the leading position at high thickness. Meanwhile, in\nFig. 4d (see Fig. R2 for a screenshot), our sample exhibits lower temperature at the\nsame detection distance and laser power when compared to the bare aluminum film,\nillustrating that the X-fabric can suffer shorter maximum detectable distance by laser\nand demonstrate good laser camouflage potential.\nFig. R1. A screenshot of the revised Fig. 3g-h (Page 13).\nFig. R2. A screenshot of the revised Fig. 4d (Page 16).\nWe also understand the reviewer’s concerns on negative effects of LWIR\nemissivity by increasing laser absorption and we have found corresponding solutions\nin our subsequent research. We have tried the technique of blade coating and the\nprepared sample can improve the laser absorption at 10.6 μm more than 20% while\nkeeping LWIR reflectivity similar to X-films (Fig. R3). It may be attributed to the better\ncrystallization during the coating process and the underlying mechanism is being\nexplored. For further optimization, it can introduce some inorganic particles or small\norganic molecules with higher absorption and more narrow width at 10.6 μm while not\ninfluencing LWIR emissivity to achieve a better balance between infrared camouflage\nand laser camouflage.\nFig. R3. The optical performance of prepared sample by blade coating. (a) Photograph\nof the sample. (b) The comparison on the mid-infrared spectrum between the sample\nand X45 film.\n3. The authors response to the question of whether the textile is suitable for cooling\nhuman beings is not well supported. The authors claim: “The aforementioned works are\nmainly aimed at extremely hot environments like summer daytime or thermal localized\nscenes like heat island cities, where the ambient temperature is higher than human body\nand it is necessary to isolate the external energy.” Neither of these are true. For example,\nnet heating can occur at moderately hot environments even when emitters radiate to the\nsky. https://www.sciencedirect.com/science/article/pii/S2666386424003345. For their\ndesign, its going to be much worse, as radiation to the window is minimized. The\nauthors also compare the cooling performance of their design to bare aluminium, which\nis a strange baseline to be using for a wearable.\nResponse:\nThanks a lot for this comment. In the mentioned work [Cell Rep. Phys. Sci. 5,\n102065 (2024)], the net heating occurs because the input power is higher than the\nradiant power from human body (Fig. R4a). It usually arises in the summer daytime\ndue to the high ambient temperature (~37 ℃) and high-temperature ground (>50 ℃)\nexposed to intense sunlight. In this situation, ground and ambient will become heat\nsource and radiate more heat to human body, thus negating or overwhelming the LWIR\nradiative cooling from human body to space. However, the scenarios for camouflage\nand cooling are diverse, which involve other time periods such as summer nighttime,\nspring and autumn (Fig. R4b). Under these circumstances, the ambient and ground will\nhave lower temperature than human body and serve as heat sink to dissipate heat from\nhuman body, thus achieving net cooling in human body. In our design, although the\nLWIR radiation is suppressed to achieve infrared camouflage, X-film can also achieve\ncooling performance through the non-atmospheric window (5-8 and 14-20 μm) by\ndissipating heat to ambient and ground.\nThen, we choose bare aluminum foil as control group to compare the cooling\nperformance because it has broadband low emissivity in 2.5-20 μm which can serve as\nthe alternative to a series of low emissive fabrics with similar optical properties in the\nprevious works [2, 3]. We hope to obtain the cooling effect as accurately as possible by\ncontrolling similar parameters such as material structure and thickness between the\nexperimental group and the control group.\nFig. R4. Schematic of energy flow among ground, ambient and human body. (a) The\nsituation in summer daytime. (b) Situations in summer nighttime, spring and autumn.\n[1] J. Mandal et al., Radiative cooling and thermoregulation in the earth’s glow. Cell\nRep. Phys. Sci. 5, 102065 (2024).\n[2] Y. Zhang et al., A waste textiles-based multilayer composite fabric with superior\nelectromagnetic shielding, infrared stealth and flame retardance for military\napplications. Chem. Eng. J. 471, 144679 (2023).\n[3] H. Ma et al., Double-sided functional infrared camouflage flexible composite fabric\nfor thermal management. Ceram. Int. 49, 16422-16432 (2023).\n4. In response to remark 7 about camouflage via reflection being tricky, the authors note\nthat “This problem can be solved by regionalized customized design through the\nthickness of nylon fibrous membrane and the load mass of pigment particles” but would\nthat not change the emissivity? Isn’t a better solution to just make the underlying\naluminium rough? The information in Supplementary Figs. 23 and 24 is not clear.\nResponse:\nThanks very much for this comment and we apology for the fuzziness of the\ndescription. The emissivity will become high by increasing the thickness of nylon\nfibrous membrane and the load mass of pigment particles, but it is also our purpose. We\nhope to match the color between sample and ambient in the infrared camera better by\nadjusting the emissivity to reduce the reflection of the sky’s thermal radiation on the\nsurface while maintaining the same color. The cold infrared signal observed at the\nshoulder in the original manuscript is due to the low emissivity of sample. Under the\nsynergistic influence between the radiation from human body (~37 ℃, low proportion)\nand reflection of the sky’s radiation (~-15 ℃, high proportion), the total radiation on\nthe sample’s surface entering the infrared camera is less than that of ambient (~20 ℃),\nthus leading to the cold signal of sample in the infrared image. As shown in\nSupplementary Fig. 25c (see Fig. R5 for a screenshot), when the human body (object)\ntemperature is 37 ℃, if the emissivity of object surface is low (blue area), it is suitable\nto the ambient (background) which has low emissivity of ~0.2. However, the emissivity\nof actual scenario such as shrubberies is almost 0.9, thus the emissivity of the object\nsurface should be increased. Otherwise, it will appear too blue in the infrared image.\nHence, we achieve better infrared camouflage effect by regionalized customized design\nespecially at the shoulder area through increasing the thickness of nylon fibrous\nmembrane and the load mass of pigment particles in the revised manuscript.\nCertainly, surface treatment of the aluminum foil such as becoming rough as the\nreviewer pointed out is also a good solution to mitigating the problem on the thermal\nradiation. It is also verified effective by the work, which shows that the surface with\nlow specular reflectance can reduce the peak value of the target-ground contrast\ncompared to the low-emissivity smooth surface (Fig. R6) [1]. We expect that it will\nexhibit better infrared camouflage performance by combining PA66 fibrous membrane\nwith this type of substrate.\nFig. R5. A screenshot of the revised Supplementary Fig. 25c (Page 34).\nFig. R6. A screenshot of the cited literature [1]. (a) Schematic representation of the\nexperimental setup. The target object surface is divided into two parts (blue and yellow).\nThe blue part is covered with I) the low-e smooth surface or II) the low-e Lambertian\nsurface to test the camouflage performance. The yellow part is covered with a\nblackbody (III) to show the real temperature of the target surface. A hot object is stuck\nonto the top of a toy car and passes by the target object. An infrared camera is set aside\nfor monitoring. (b) Indoor experimental results. (c) Outdoor experimental results. Five\ncaptured frames (i–v) are presented in each case, for both the low-e Lambertian surface\nand the low-e smooth surface.\n[1] Y. Huang et al., Infrared camouflage utilizing ultrathin flexible large-scale high-\ntemperature-tolerant Lambertian surfaces. Laser Photonics Rev. 15, 2000391 (2021).\nTo clarify this problem, we have revised the manuscript as follows:\nPage 15, Line 384\n“As an example, the devised brown X-film showed a similar color to sand and it could\nprovide excellent infrared camouflage for electronic equipment like a fully operational\nmobile phone (Supplementary Fig. 26). Furthermore, the surface treatment of substrate\nis also beneficial for X-films to achieve better infrared camouflage performance against\nvarious surroundings 64.”\n5. Related to #4, the authors’ work and the controls they use encouraged us to look at\nIR camouflage uniforms. It seems Ghillie suits, which are loose fitting and thus closer\nto ambient temperature due to convection rather than temperature of the object to be\ncamouflaged, are quite good at thermal camouflaging. Existing thermally camouflaged\nvariants of these designs may already do the job quite well. It may be worthwhile to\ncompare such designs (e.g. https://blog.beezcombatsystems.com/predator-ghillie-\nspectralflage.html) against the design proposed by the authors. That would be better\nthan using aluminium as a control.\nResponse:\nWe thank the reviewer very much for this constructive comment and the control\nsample provided. First, it needs to be stated that the product in the website mentions\n“While this system exponentially excels at outline breakup and mitigating heat\nsignature to thermal threats, the laws of convection still apply”, this indicates the\nsurface design of Ghillie suits is beneficial to breakup and minimize the heat signal\nfrom human body but will not influence the effect of convection (Fig. R7). The reason\nwhy Ghillie suits can achieve infrared camouflage performance is mainly due to low\nheat conductivity based on the porous structure of clothes. Generally, Ghillie suits\nconsist of numerous strips and knots which form a fluffy multilayer three-dimensional\nstructure. It can serve as a thermal insulation layer between human body and the\nexternal environment, thus reducing the radiative heat radiation on the surface. The\nproduct presentation also mentions “Increased distance between the user's body heat\nand the blanket is better”, which is also due to the regulation on the heat conductivity\nbetween human body and the Ghillie suits so that the infrared radiation will be reduced.\nHowever, Ghillie suits have some disadvantages: (ⅰ) Ghillie suits are very heavy\nbecause they are made by joining together numerous strips of fabric, which restricts the\nmovement of the wearer. (ⅱ) Ghillie suits achieve infrared camouflage by reducing heat\nconductivity so it is difficult for human body to dissipate heat, which will result in\nuncomfortable feeling for the wearer especially in the long-term stealth. In comparison,\nour design achieves infrared camouflage by adjusting the surface emissivity, making\nthe material lightweight and possess passive heat dissipation capability. As a result, it\nis more suitable for long-term camouflage. For future optimization, the method\ncombining selective infrared emissivity regulation and heat conductivity adjustment\nmay achieve better thermal camouflage products.\nThen, we choose bare aluminum foil as control group because it has broadband\nlow emissivity in 2.5-20 μm which can serve as the alternative to a series of low\nemissive fabrics with similar infrared properties in the previous works [1, 2]. By\ncontrolling similar parameters such as material structure and thickness between the\nexperimental group and the control group, it is clearer that our sample can achieve\nvisible camouflage, cooling performance and laser camouflage while maintaining\ninfrared camouflage.\nFig. R7. The product presentation of Ghillie suits from the website\n(https://blog.beezcombatsystems.com/predator-ghillie-spectralflage.html).\n[1] Y. Zhang et al., A waste textiles-based multilayer composite fabric with superior\nelectromagnetic shielding, infrared stealth and flame retardance for military\napplications. Chem. Eng. J. 471, 144679 (2023).\n[2] H. Ma et al., Double-sided functional infrared camouflage flexible composite fabric\nfor thermal management. Ceram. Int. 49, 16422-16432 (2023).\nResponse to Reviewer #5\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports.\nThis is part of the Nature Communications initiative to facilitate training in peer review\nand to provide appropriate recognition for Early Career Researchers who co-review\nmanuscripts.\nResponse:\nThanks very much to the Reviewer #5 for co-reviewing this manuscript and\nproviding insightful suggestions, which are helpful to further improve the work."}, {"round": 3, "reviewer_comments": {"reviewer_3": "[Editor's Note: This reviewer was asked to also evaluate the response to Reviewer #4's comments]\nMy concerns have been addressed. And I think the authors address Reviewer #4's concerns well. I suggest acceptance."}, "author_response": ""}]

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