One-step fabrication of superhydrophobic fabrics with stable mechanical performance in harsh conditions

Domain: physics
Published: 2026-03-20
Editorial outcome: minor_revision

Abstract
Developing robust water-repellent textiles is critical for outdoor, protective, and industrial applications. However, achieving long-lasting water repellency under mechanical stress remains a significant challenge. Conventional approaches typically rely on nanoparticle assemblies or PFAS-based finishes, which often detach or degrade when subjected to abrasion or harsh conditions. Here, we demonstrate a molecularly assembled robust superhydrophobic shell (MARS) technique that directly constructs an ordered, covalently bonded, fluorine-free silica shell on individual yarn fibers via a one-step process. MARS eliminates the need for discrete nanoparticles or fluorinated chemistries and is compatible with a wide range of natural and synthetic fibers. This fiber-level treatment maintains superhydrophobicity even after the fibers are woven or knitted into finished textiles, while preserving breathability and mechanical resilience. MARS combines biomimetic inspiration with practical, scalable fabrication to meet urgent performance needs. Unlike conventional coatings that progressively degrade, the permanently bonded MARS coating endures intensive abrasion, high-velocity water impacts, steam exposure, and extreme temperature cycles. By addressing key challenges such as PFAS restrictions and the fragility of traditional coatings, the MARS method paves the way for next-generation water-repellent fabrics that balance sustainability and high performance across outdoor, protective, medical, and industrial applications.

Introduction
Superhydrophobic fabrics are designed to repel water, resist staining, and remain lightweight and breathable in demanding applications1. Depositing fluorinated compounds nanoparticle coatings2–5, silicone nanofilament6, 7 coatings or silane-based interpenetrating networks on various textiles6-8 can achieve superhydrophobicity, initially providing effective water repellency3,9. However, such treatments lack long-term durability, as the weak adhesion between particles makes them prone to abrasion and fabric deformation4. Moreover, nanoparticle layers can seal the interstitial pores of fabrics5, 9, 10, which increases weight11, diminishes breathability, and adversely affects the fabric’s hand and drape, limiting their suitability for lightweight, durable outdoor garments1. Environmental and health concerns further complicate the reliance on fluorinated finishes12. Regulatory restrictions against per- and polyfluoroalkyl substances (PFASs) have intensified due to their environmental persistence, potential toxicity, and associated health risks13, prompting the textile industry to seek sustainable, non-fluorinated alternatives that offer comparable durability14.

Biomimetic inspiration offers a path forward15. Lotus leaves16,17, Salvinia leaves18, insect wings19, penguin feathers20, and the cuticles of soil-dwelling springtails21, 22 exhibit fluorine-free superhydrophobicity in nature. Springtails, tiny soil-dwelling arthropods, offer a remarkable example through their in-situ superhydrophobic skin23, which enables survival in wet, abrasive environments (Fig. 1a). The springtail’s skin combines mushroom-shaped microstructures and nanoscopic ridges to repel water21, prevent contamination22, and resist mechanical damage23 (Fig. 1b). This natural design has inspired robust coatings on rigid substrates15, 24, 25, but translating such micro–nano architectures to flexible, breathable textiles has remained challenging.

Motivated by the springtail cuticle and the pressing need for sustainable water-repellent fabrics, we developed an in-situ molecularly assembled robust-superhydrophobic shell (MARS) technique that covalently anchors a carbon-chain silane/SiO2 network directly onto fiber surfaces through a one-step molecular assembly, creating continuous superhydrophobic shells at the fiber level without the need for discrete nanoparticles. Incorporating long-chain alkyl silanes into the silica matrix yields an interpenetrating, crosslinked network that retains hydrophobicity under severe abrasion, high-pressure water jets, and steam exposure. By treating fibers before textile formation, MARS endows both yarns and the resulting fabrics with permanently bonded, fluorine-free superhydrophobicity while maintaining breathability, tensile strength, and flexibility.

Results
Molecular assembly robust superhydrophobic shell on fiber

The MARS modification process involves continuously coating twisted yarns with a fluorine-free solution that reacts rapidly in humid air to form a covalently bonded, nanostructured silica shell functionalized with long alkane chains (Fig. 1c). The process begins by passing twisted yarns (150D, 36F; yarn radius ~150 µm; single‐fiber diameter ~10 µm) through a petroleum ether solution (boiling point 30-60°C) containing 4% (w/v) tetrachlorosilane (TCS) and 2% (w/v) octadecyltrichlorosilane (OTS) at a linear speed U of 0.25 m·s-1 (Supplementary Fig. 1, Supplementary Movie 1). MARS utilizes low-cost raw materials and a simple, energy-efficient process. TCS and OTS are industrially available silanes. TCS is a byproduct of high-purity silicon production and serves as a key raw material in the silicon and rubber industries26. Additionally, TCRS can be recycled from silicone waste, offering a cost-effective solution with high recycling potential27. TCS, with its lower steric hindrance, reacts more rapidly with the hydroxyl groups in cellulose-based natural fibers28 (e.g., cotton, linen; see Supplementary Fig. 2). The low viscosity (η ≈ 0.3 mPa·s) and surface tension (γ ≈ 24.3 mN·m-1) of the carrier solvent yield a capillary number Ca = ηU/γ ~ 10-3, entraining a uniform liquid film of thickness e = 1.37 d Ca2/3 (on the order of 100 µm, where d is the yarn diameter)29. This coating corresponds to a modest increase in yarn mass of approximately 6.1%. Additionally, the use of petroleum ether enables solvent recycling during condensation, enhancing fabrication efficiency. Based on our estimates, treating a 170 g cotton fabric (1 m2) costs only about $0.27 (roughly $1.56 per kg of fabric), which can be reduced to ~$0.12 (∼$0.69 per kg) if ~75% of the solvent is recovered, indicating that the MARS treatment is economically feasible for large-scale manufacturing.

Within seconds of exiting the bath, the solvent evaporates (Supplementary Fig. 3), and ambient moisture hydrolyzes TCS (owing to its smaller molecular size compared to OTS)30, preferentially undergoes rapid hydrolysis and condensation to form an amorphous SiO2 network covalently grafted to available –OH groups on natural fibers (Supplementary Fig. 2). Subsequently, OTS reacts at the newly formed silica surface, anchoring C18 alkyl chains that dramatically lower the surface energy31, analogous to plant wax layers16,17, without the need for perfluorinated reagents12 (Supplementary Fig. 4). The resulting architecture on yarns comprises 36 individual fibers (~10 µm diameter each) with mushroom-like silica aggregates (130-170 nm in diameter) and tightly adhered silica shells (20-50 nm feature size) on their surfaces (Fig. 1d, Supplementary Fig. 5), demonstrating a hierarchical coating structure. On synthetic substrates lacking native hydroxyl groups (e.g., polyester, nylon), the low-polarity, small-molecule TCS penetrates slightly into the fiber surface, where it crosslinks in situ to anchor the amorphous SiO2 network onto the fibers, ensuring broad material compatibility (Supplementary Fig. 5). This sequential, self-separating reaction yields a distinct shell nanostructure (Supplementary Fig. 5). The TCS-derived silica forms a robust inner skeleton covalently bonded to the fiber surface, while OTS forms an outer hydrophobic layer (Supplementary Fig. 6). We hypothesize that this covalently integrated core–shell architecture is key to the coating’s exceptional mechanical durability.

Next, we evaluated superhydrophobicity at the single-fiber scale using a contact angle tensiometer32 equipped with a 20× magnification lens. Even 20 pL droplets (~30 µm diameter) exhibited an apparent contact angle θ of 160.0° on individual cotton fibers (Fig. 1e). Wool, polyester, and nylon fibers all demonstrated superhydrophobic behavior, with θ values of 157.6°, 163.0°, and 156.5°, respectively (Supplementary Fig. 7). Environmental scanning electron microscopy at 3.7°C and 100% relative humidity33 further revealed that a condensing microdroplet (<2 µm diameter, ~6 fL) on a single fiber will roll off once it grows to ~2 µm in size, demonstrating excellent water repellency even under cool, saturated conditions (Fig. 1f).

Finally, MARS-modified yarns were fabricated into woven and knitted textiles and even used to embroider superhydrophobic motifs onto untreated fabrics (Fig. 1g-i). The MARS-textiles exhibited high apparent water contact angles of 154.7° (woven) and 156.1° (knitted) (Fig. 1g, h), as well as ultralow sliding angles of 1.8° and 3.0°, respectively. The droplet rests only on the texture tips, with air trapped in the hollows beneath, forming a Cassie–Baxter state34 (Fig. 1h, Supplementary Movie 2), which prevents water from penetrating into the fabric. The observed Cassie–Baxter superhydrophobicity is attributed to the textiles’ three-tier hierarchical milli-/micro-/nanostructures35, a dense yet rough surface texture at the nanoscale2, 9, and the low surface energy imparted by the alkyl-silane modification (Fig. 1d, h). Moreover, embroidered patterns in multiple colors (light/dark green and pink) maintained θa ≈ 161.5° on a lotus-flower motif, whereas the surrounding untreated fabric readily absorbed dyed water (Fig. 1i). Across all color variants, ΔE* color shifts36 remained below 1.0, indicating that the thin silica shells preserve the original hues and protect fibers from mechanical stresses during weaving, knitting, and embroidery (Supplementary Fig. 8).

Water-repellent evaluation of MARS-modified fibers

We applied the MARS modification to everyday apparel items. A white T-shirt, black leggings, and a white shoe vamp (upper) (Fig. 2a, Supplementary Fig. 9) and compared their water-repellency against fabrics coated by conventional spray-on treatments (Ultra-Ever Dry and a Capstone ST-200 + fused silica mixture) (Fig. 2a). In a continuous water-impact spray test (based on AATCC 22)37, MARS-modified fabrics withstood over 25 liters of water sprayed before any wetting occurred, surpassing the standard 250 mL-per-impulse benchmark by a factor of 100 and achieving the highest AATCC spray rating of 100 (Fig. 2b, Supplementary Movie 3). Similar resistance was observed against various common liquids, including beverages and carbonated soft drinks, demonstrating robust repellency under real-world spill conditions (Supplementary Fig. 10a). Significantly, the water repellency was retained across a broad spectrum of textile substrates, including natural fabrics (linen, cotton, wool) and synthetics (spandex, nylon, acetate, polyester), highlighting the versatility of the MARS modification process (Supplementary Fig. 10b).

Under millimeter-scale water droplet impacts (25°C, Weber number ~5.4), individual drops consistently bounced off the fabric surface up to six times (Fig. 2c). In simulated heavy rain tests, the MARS-modified fabric resisted 12 hours of continuous raindrop impacts, withstanding over 104 impacts at a single point (2.5 drops per second, impact velocity 2.4-3.0 m·s−1) (Fig. 2d, Supplementary Fig. 11a-c). To further challenge the coating's resistance to high-speed water, we designed a rotational-jet impact setup (Supplementary Fig. 11d, e, Supplementary Movie 3). Whereas conventional superhydrophobic coatings failed when impacted by droplets at 5.0-6.6 m·s-1, the MARS-modified fabrics effectively repelled water drops impacting at 11.6 m·s-1, equivalent to the velocity of a raindrop during a 100-meter sprint (Fig. 2e).

In the Bundesmann rain-shower test, which subjects textiles to kinetic energies far exceeding those of natural downpours (~5.8× a cloudburst, 90× heavy rain, 480× moderate rain, 21,000× light rain)38, a canvas fabric spray-coated with Capstone-FS lost its repellency, receiving an AATCC score of 50 (~70% of its surface wetting) and allowing 243.7 mL of water to penetrate. In stark contrast, the MARS-modified canvas achieved an AATCC score of 100 with only 1.7% water absorption and almost no water penetration (Fig. 2f, Supplementary Fig. 12). Moreover, under standard machine laundering with detergent2,37, MARS-modified fabrics retained their superhydrophobic performance, scoring AATCC 100 after five wash cycles and AATCC 95 after twenty cycles, with static contact angles remaining above 150° throughout (Supplementary Table 1).

Durability and Wear Resistance

Every day use always involves rubbing against sleeves or backpack straps, or repeated handling of garments, which subjects textiles to abrasion, peeling, and stretching that can easily damage the fine micro- and nano-structures or weakly bound layers responsible for water repellency1,4,5. To evaluate the practical wear resistance of MARS, we conducted both standardized laboratory abrasion tests and application-specific simulations, including Martindale and Taber abrasion tests, falling-sand impact, vibration, stretching, peeling, scrubbing, and treadmill running.

In the Martindale test, MARS-treated canvas fabric endured up to 80,000 abrasion cycles against a standard wool fabric under 9 kPa pressure while maintaining a θ > 150° and minimal contact angle variation (Δθ < 5°) (Fig. 3a, Supplementary Movie 4). Unlike conventional coatings that degrade after only a few hundred cycles1,4, the MARS-modified fabrics demonstrated exceptional durability. Notably, in the more aggressive Taber test (a 250 g load for 20,000 cycles), the MARS-treated fabrics retained superhydrophobicity (θ ≈ 156.7°) with a slight apparent contact angle drop (Δθ ≈ 8.8°). In the Taber test, SEM images (Supplementary Fig. 13, inset ) confirm that even after 20,000 abrasion cycles, the nanostructured MARS shell remains intact on the fiber surface, providing direct visual evidence of the coating’s robustness.

Compared with previous durable superhydrophobic treatments, such as silicone nanofilament coatings6, 7, 39, silica nanoparticles40 and perovskite-silane composite fibers8, the covalent bonding of MARS offers a distinct advantage in mechanical robustness. Silicone nanofilaments typically adhere to fibers via physical entanglement or physisorption. In contrast, MARS forms a molecularly assembled interpenetrating network shell that is chemically grafted to each fiber’s surface (Supplementary Fig. 4). The nanostructured silica shells, securely embedded within the fiber matrix, significantly outperformed conventional nanoparticle-based coatings, with a reduced abrasion depth of 46.2% (Fig. 3b, Supplementary Fig. 13, Supplementary Movie 4). In falling sand tests1,37, where impacts from quartz sand abrade fabrics, MARS-treated samples withstood 100 cycles of implications from a total of 320 kg of sand while maintaining their water-repellent properties (Fig. 3c).

We assessed the effect of the MARS coating on the textile’s tactile properties, as coating processes often compromise fabric feel. As shown by quantitative fabric hand measurements (Fig. 3d and Supplementary Table 2), the MARS-treated fabric is virtually indistinguishable from the untreated control in key haptic metrics such as bending rigidity and surface roughness (e.g., 31.7 gf·mm/rad vs. 31.1 for control; surface roughness ~7.6 µm vs ~7.4 µm for control). This provides strong evidence that MARS’s ultrathin coating imparts robust functionality without sacrificing the fabric’s natural softness, drape, or breathability, unlike many conventional coatings that stiffen the textile.

To simulate real-life wear under motion, MARS-treated fabrics were integrated into garments and subjected to various usage scenarios. A MARS-treated T-shirt was worn during a 1-hour treadmill run with a backpack (Fig. 3e), where the shoulder straps caused frictional oscillatory motion similar to that experienced during running and jogging41. In a mimetic vibration test (harmonic shoulder-strap rubbing at 2 Hz, 2 mm amplitude), the coating withstood over 600,000 friction cycles with no significant loss of superhydrophobicity (Fig. 3f). In addition, a knitted MARS fabric retained superhydrophobicity after 20,000 stretch cycles, surviving extensive fiber-to-fiber abrasion (Fig. 3g). For practical footwear, MARS-modified shoe uppers endured 8,000 brushing strokes (simulating vigorous cleaning) with negligible pilling or change in water repellency (Δθ < 3.2°) (Fig. 3h, Supplementary Movie 4). Even after 500 cycles of 3M tape peeling at 90°, the MARS fabric’s θ remained ~155° (Δθ ≈ 9.1°) (Fig. 3i, Supplementary Fig. 14).

Beyond apparel, we tested MARS-treated socks under sustained load. A wearer ran 15,000 steps on a treadmill, exerting ~51.3 kPa pressure per step (Fig. 3j). Conventionally treated socks (Capstone-FS) showed visible white residue from coating abrasion and lost water repellency (contact angle dropped to ~139.7°). In contrast, MARS-treated socks maintained their water-repellent properties without noticeable degradation (Δθ only ~1.7°) (Fig. 3k, Supplementary Movie 4). Finally, to assess long-term outdoor performance, MARS-modified fabrics were exposed to the natural environment for 360 days (Supplementary Fig. 15a), spanning all seasons and including high solar radiation, sandstorms, rain, frost, and icing (temperatures from -16.8 to 41.2°C; humidity 9% to 100%). Supplementary Fig. 15b summarizes the temperature, rainfall, and light conditions during this year-long exposure. A MARS-modified T-shirt showed only ~15% color fading36 after one year (compared to ~45% for an untreated control). It maintained superhydrophobicity throughout (Supplementary Fig. 15c). Even after extensive abrasion and washing, the treated fabrics maintain very low sliding angles (<5°) (Supplementary Fig. 16, SEM images in Supplementary Table 3). These results demonstrate that the MARS technique endows fabrics with exceptional durability and wear resistance, enabling them to retain superhydrophobicity under a variety of mechanical stresses and environmental conditions, making them suitable for practical, long-term use in garments and outdoor applications.

Robust Superhydrophobicity under Harsh Conditions

Superhydrophobic textiles are also sought for preventing scalding injuries from hot liquids soaking into clothing, yet most existing water-repellent garments are ineffective against very hot fluids42,43. MARS-modified textiles demonstrated excellent repellency even for hot water. When 85°C water droplets (Weber number ~15) impacted the fabric, they still bounced off cleanly (Fig. 4a). Tests with a continuous hot water jet (85°C, ~0.5 m·s-1 flow) and a burst of hot coffee steam (100°C, 9 bar pressure, 150 mL) showed consistent water-repellent performance (Fig. 4b, c; Supplementary Movie 5), far more effective than a comparable fluorinated treatment44. Even under extreme alternating thermal conditions, MARS-treated fabrics withstood sequential jetting with boiling water (95°C, 250 mL, 30 s), liquid nitrogen (-196°C, 250 mL, 200 s), and boiling water again (95°C, 250 mL, 30 s), yet still retained superhydrophobicity at the end (Fig. 4d, Supplementary Fig. 17, Supplementary Movie 5).

Another challenge for hot liquid repellency in textiles is resistance to steam. After exposure to 160°C steam, MARS textiles immediately shed water droplets, whereas perfluorosilane-treated controls became wetted by the steam (Fig. 4e, f, Supplementary Movie 5). Low-field NMR measurements revealed that steam-exposed PFAS-treated samples retained free-water signals lasting ~2000 ms. In contrast, MARS fabrics showed only weak, long T2 signals corresponding to semi-free water, evidencing that the covalent silica network effectively blocks vapor condensation (Supplementary Fig. 6f). PFAS-free MARS superhydrophobic coatings thus provide more reliable hot-water protection. Furthermore, the high-density covalent bonding in the MARS coating ensures stability under steam. When we sealed a bottle of boiling water with a spray-coated superhydrophobic fabric (Capstone-FS), steam became trapped and condensed within the fabric pores29,45, destroying its breathability. By comparison, the MARS-modified fabric allowed steam to pass through (evidenced by condensed water appearing on a glass slide above the textile), and water droplets impacting the fabric opening simply rolled off (Supplementary Fig. 18).

The MARS modification collectively enhances long-term water repellency, wear resistance, and steam resistance, addressing three key challenges faced by superhydrophobic textiles. The high-density silica network in MARS confers superhydrophobicity. It traps a stable air layer at the textile-water interface, which is vital for maintaining breathability and reducing drag in water17,46, similar to the water-shedding strategy of penguin feathers20. Air permeability tests47 confirmed that the treated fabric allows rapid airflow and maintains breathability over extended periods (≥13.5 hours, Supplementary Fig. 19, Supplementary Movie 6). In dynamic underwater tests, MARS-treated leggings effectively repelled water during repeated kicking motions in a swimming pool (Fig. 4g). The fabric maintained a stable plastron air cushion48, as evidenced by strong light reflection, even at a flow velocity of 2.0 m·s-1 in a water tunnel (Fig. 4h, Supplementary Fig. 20, Supplementary Movie 7). Moreover, MARS textiles exhibited a ~40% drag reduction compared to untreated fabrics over 1 hour at a flow rate of 0.5 m·s-1 (Fig. 4i).

The coating’s safety is our final concern. We conducted cytotoxicity and cell proliferation assays (5-day CCK-8 test using NIH 3T3 fibroblasts) to evaluate the MARS coating’s safety (Supplementary Fig. 21). The results showed no significant difference in cell viability or growth between the MARS-coated fabric and an untreated control. In contrast, a fabric treated with a PFAS-based water repellent (Capstone-FS, containing PFOS) exhibited only about half the viable cell count of the other two groups by day 5. MARS is analogous to silica (sand/glass) combined with long-chain paraffin wax, the materials of which are widely regarded as inert, non-toxic, and biocompatible.

Methods
Superhydrophobic Fabric Preparation

Materials and Reagents Natural fibers (cotton, wool, and linen) and synthetic fibers (nylon and polyester) were obtained from Haixu Fiber Products and kindly provided by ANTA Sport. LINING kindly supplied the Jacquard-woven shoe upper. Reagents for superhydrophobic treatment include tetrachlorosilane (TCS), octadecyltrichlorosilane (OTS), and anhydrous petroleum ether (anhydrous grade), which were purchased from Alfa Aesar. Carbon nanofibers (100 nm diameter, 20-200 μm length) served as substrates for TEM imaging of the amorphous SiO2 network (Supplementary Fig. 5a), which were purchased from Sigma-Aldrich.

The superhydrophobic coating process is performed using a homemade device in a fuming hood. Twisted yarns (150D, 36F) were continuously drawn through a petroleum ether solution containing 4 wt% TCS and 2 wt% OTS at a linear speed of 0.25 m·s−1. The take-up speed of the winding machine (HR3688, Hangzhou Hengji Machine Co. Ltd.) controlled the reaction time in the solution, and silane concentrations were optimized to yield a uniform silica shell coating (Supplementary Fig. 1-3). Then, the fibers were dried in humid air (relative humidity, RH 95%) for several seconds to allow solvent evaporation and silane hydrolysis to occur.

Coated yarns were then processed into textiles, with weaving and machine knitting carried out by Xiexin Worsted Spinning Weaving and Dyeing Co., Ltd. in Wuxi, China. To produce patterned superhydrophobic motifs, MARS-treated yarns were embroidered onto untreated fabric substrates using standard embroidery machines (Innovis brother-NV180, Japan). The T-shirt shown in Supplementary Movie 3 was knitted using cotton yarns that were pre-treated via the continuous MARS process by Sinotex SNT-803S (Hi-Tech Group Corporation, China). The detail weaving process was shown in Supplementary Movie 8.

For comparison, identical fabrics were spray-coated with (1) hydrophobic nanobeads (Ultra-Ever Dry, Ultratech International) and (2) a 1:1 mixture of Capstone ST-200 (DuPont) and fused silica (Aerosil R202, Evonik).

Characterization of MARS Treated Fabric

Characterization and Measurements Optical images were captured with a digital camera (Nikon D750, Japan). Surface morphology and stereomicroscopic images of abraded areas were obtained using a stereomicroscope (Olympus DSX1000, Japan). Scanning electron microscopy (SEM) was performed using a field-emission scanning electron microscope (Hitachi SU8010, Japan) at an accelerating voltage of 5 kV. The samples were sputter-coated with a thin platinum layer (Leica EM ACE600, Germany). Transmission electron microscopy (TEM) images were acquired on a FEI Tecnai G2 F20 (USA) at 200 kV, using carbon nanofiber substrates to visualize the amorphous SiO2 network. High-resolution microcomputed tomography (micro-CT; Bruker SkyScan 1272, USA) was used to visualize the water-solids interface within droplets on the superhydrophobic textiles. A droplet seated on the textiles was mounted in a custom holder, and dynamic scanning commenced before the liquid reached the notched region. Projections were recorded at 4K resolution (6.0 μm voxel size) and optimized at an X-ray energy of 30 keV. X-ray photoelectron spectroscopy (ThermoFisher ESCALab 250Xi, USA) was used to determine the elemental composition of the treated fabrics. Low-field nuclear magnetic resonance (LF-NMR; Niumag VTMR20-010V-I, China) was used to characterize the water-binding properties in treated fibers. Scrub resistance was test by QFS-scrub resistance tester (Shanghai Meiyu Technology Instrument BH14J, China). Figures 2a, b, d, e, f; 3a, b, g, h, i; Supplementary Figures 1a, 8a, b, and 20a were created using PS software.

The color fastness of the MARS-modified fabrics was evaluated using a colorimeter (CHNSpec DS-220, China) to calculate color differences before and after modification. We utilized the CIE L*a*b* color space model, which enables the calculation of color differences based on lightness (L*), red-green (a*), and yellow-blue (b*) components. The color difference, ∆E*=√(L1-L2)2+(a1-a2)2+(b1-b2)2, where L1, a1, and b1 are the color coordinates before MARS modification, and L2, a2, and b2 are the coordinates after modification. The whiteness of the MARS-modified fabrics was evaluated by a whiteness meter (Qiwei WSB-1, China).

Water Repellency and Contact Angle Measurement

Static water contact angles were measured on fabric surfaces using a KRÜSS DSA 25S goniometer (Germany) with 2.0 μL droplets and a KRÜSS DSA 30M drop-shape analyzer equipped with a 20× microscope objective and piezoelectric micro-dosing head for 20–200 pL droplets. Static water contact angles were measured with a contact angle goniometer across droplet diameters from 10 µm to 2 mm to evaluate hydrophobicity over a range of scales. Each fabric sample was tested at five distinct locations; the reported values represent the mean ± standard deviation.

Liquid jets impact test

High-speed imaging of droplet and sand impacts was performed using a PHOTRON FASTCAM Nova S20 (Japan) at a frame rate of 1,000 fps. Droplets (D = 1.0 mm) were released from a needle positioned 10.0 mm above the fabric to achieve an impact velocity of 0.45 m·s-1. Side-view dynamics were captured at 10,000 frames per second (fps) with backlighting to determine impact velocity and contact time. A Harvard Apparatus micro-injection gear pump (USA) controlled liquid flow rates. When testing hot water (25°C vs. 85°C), surface tension γ decreases from 72 mN/m to 62 mN/m. Continuous liquid-jet impacts were recorded with a PHOTRON FASTCAM Nova S20 and a macro lens at 2,000 fps. Infrared thermography was conducted with a FLIR A600 camera (USA).

Wash test

MARS-treated, Capstone-FS-treated, and Ultra-Ever Dry-treated fabric samples (20 × 20 cm) were laundered in a standard home washing machine (high-efficiency front-loading type). After each wash cycle, water repellency was evaluated using the AATCC 22-2017 spray test standard. In this test, 250 mL of distilled water is poured through a funnel with 19 holes (each ~0.86 mm diameter) from 150 mm above the fabric, which is held at a 45° angle. The fabric’s wetting is assessed by the amount of water sticking to the surface, the number of wetted spots, and the area wetted. Each fabric was tested in triplicate. Detailed laundering conditions followed AATCC LP1-2021 for machine washing, using AATCC standard reference detergent (AATCC M1-2017e). Key wash parameters included: a 15 ± 4 L water fill, 1.8 ± 0.1 kg load, 50 ± 1 mL detergent, agitation at 45 ± 10 rpm for 11 ± 1 minutes, 2 rinse cycles, final spin at 1300 ± 150 rpm for 12–18 minutes, and wash water temperature 25 ± 3 °C (see Supplementary Table 5 for the full set of parameters).

Abrasion Resistance (Martindale, Taber test)

Abrasion resistance was evaluated using Martindale and Taber testers (Darong Textile Instrument, China). Martindale test was performed following ASTM D4966. Fabric samples were secured to the Martindale head and abraded against standard wool felt under a pressure of 9 kPa in a Lissajous pattern for 80,000 cycles. The Taber test was performed in accordance with ASTM D4060. Circular fabric specimens (100 mm diameter) were mounted on a rotating platform, and two counter-rotating CS-10 grinding wheels (each with a 250 g load) rubbed the sample for up to 20,000 cycles, generating both inward and outward wear tracks. Abrasion depth was evaluated by observing changes in thickness and appearance by a stereo microscope (Olympus DSX1000T, Japan). After every 2,000 cycles, static contact angles were re-measured to confirm sustained superhydrophobicity.

Peel Adhesion Test

The adhesion of the MARS layer was quantified using 3M peel tests (ASTM D3330-2018). A 3M bonding tape was applied with a 4 kg roller (two passes), left for 90 s, and then peeled at 90° using a custom fixture conforming to ASTM D6862 (ASTM D6862-2021 Standard test method for 90 degree peel resistance of adhesives) on a Mark-10 ESM303 force platform (USA). Each cycle used fresh tape. After peeling off, the local water contact angle was measured using a ~2 μL droplet.

Falling Sand Impact

Abrasion resistance under falling-sand impact was assessed per ASTM D968-2025. Silica sand (400-700 μm) was released from 91.4 cm above the fabric, striking at a 45° angle with an impact velocity of ~ 4.2 m·s-1. High-speed imaging of sand impacts was performed using a PHOTRON FASTCAM Nova S20 (Japan) at a frame rate of 2,000 fps. Post-impact, superhydrophobicity and surface integrity were evaluated using contact angle measurements and SEM imaging.

Fabric touch test

The fabric handling properties were quantified using the fabric touch tester (Darong Textile Instrument DR555FT, China). The device evaluated the four different dimensions of the untreated, MARS-treated, and Capstone-FS-treated fabric physical properties: the compression, thermal, surface, and bending properties (including pulling, pressing, pinching, kneading, and rubbing). The fabric samples were cut into an L-shaped configuration (310 × 310 mm) with 200 mm arms.

The central square region of each specimen was subjected to a downward pulling force, inducing horizontal displacement in the two arm sections. Compression properties were measured at the central area of the sample, while bending and surface characteristics were evaluated along the arm sections. To ensure measurement efficiency, the bending and surface modules were designed for duplicate testing, allowing bidirectional assessment of each sample in a single test cycle.

Environmental Durability Testing

Hot Coffee Resistance Heated coffee (> 80°C), extracted from a Starbucks Verdana Blend Americano capsule and pressurized on Dolce Gusto machines (De’ Longhi, Italy), was directly applied to MARS- and Capstone-FS-treated fabrics for 30 s (150 mL). The treated fabric samples are placed at an angle of 60°. Surface wetting state during coffee impact was monitored by infrared thermography. The impact event was recorded at 100 frames per second (fps) using a FLIR A600 camera (USA) fitted with a macro lens.

Thermal Stability Thermal cycling was performed by alternately exposing samples to boiling water (100 °C; 300 mL dispensed over 30 s via a Xiaomi Smart Water Dispenser, China) and liquid nitrogen (-196 °C; ~300 mL poured over 30 s). After each hot-cold or cold-hot cycle, static contact angles and droplet rebound behavior were re-evaluated to assess the retention of superhydrophobicity.

High-Temperature Steam Resistance Treated fabrics were placed in a splint-type steam iron set to 160°C for 10 s of direct steam exposure. After steaming, colored water was jetted onto the fabric surface, and surface wettability was recorded. Optical videos were captured at 50 frames per second (fps) using a Nikon D750 camera (Japan), while infrared thermal imaging was recorded at 100 frames per second (fps) with the FLIR A600 (USA).

Stable Air Cushion at the Fabric-Water Interface The experiment was conducted in a swimming pool. The MARS-treated legging was fitted onto a prosthetic limb, which was then submerged underwater to a depth of 5 cm by a robotic arm (R630, Beijing SDCQ Electrical Technology Co., Ltd., China) at a frequency of 10 cycles per minutes. An underwater camera (DJI Action2, China) was used to record the fabric-water interface.

Water Tunnel Experiment The drag reduction capability of the superhydrophobic fabrics was tested in a circulating water tunnel at a flow velocity of 0.5 to 2.0 m·s-1. The fabric samples were fixed in the flow stream, and the drag force was measured using a force transducer. Drag reduction efficiency was calculated as (Fcontrol - Ftest)/Fcontrol × 100, where Fcontrol is the drag force on a control (untreated) fabric, and Ftest is the drag force on the superhydrophobic fabric.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In the manuscript, Z. Liu et al. present a new approach to prepare robust superhydrophobic textiles. Robustness has been the most important property to be achieved for superhydrophobic surfaces. The suggested method is well developed, and results are reliable. In addition, this work would be of general interest to the broader audience of Nature Communication. However, for publication, there are some concerns to be solved, as below.\n1. There are several literatures about textile showing robustness and superhydrophobicity, such like silicone nanofilament studies, proposed by Stefan Seeger group (Universität Zürich Irchel). Authors should compare the properties with previous literatures more thoroughly, which make novelty stronger.\n2. In the manuscript, tetrachlorosilane (TCS) and octadecyltrichlorosilane (OTS) were used for hydrophobic coating. Can other chemicals, having longer or shorter carbon chain be used? I am wondering how they were chosen among various similar chemicals.\n3. The carbon chain length and concentrations of chemicals might change mechanical property. It would be good to show controlling mechanical property, such like how brittle are they, by varying chemicals and concentrations.\n4. Robustness was characterized by contact angles. However, I am not sure the structures are really unchanged by only contact angles. The SEM images of the structures have to be characterized after various durability tests applying stress.\n5. For repellency, dynamic contact angles are more important parameter than static contact angle. Therefore, in addition to SEM images, dynamic contact angles (contact angle hysteresis and sliding angle) have to be included.", "reviewer_2": "The manuscript describes a MARS (molecular-assembled robust-superhydrophobic shell) method that works without fluorinated chemicals and covalently binds silica/OTS/TCS networks to fibers to obtain durable superhydrophobic textiles. There are noteworthy results: The specific combination of TCS+OTS in a one-step molecular assembly on a fiber basis is new. In particular, the chemical one-step modification prior to fiber textile-processing. The durability (abrasion, vapor resistance) with simultaneous vapor permeability is also unusual and of further interest, not only for superhydrophobic textiles.\nThe authors report \"mushroom-like aggregates\" of the IPN, and the geometry of the nanostructures on the fibers has been analyzed by TEM. The authors state that TCS preferentially condenses to form a dense amorphous silica core (dark area), while OTS modifies the surface of the amorphous silica. Analysis of the TEM data suggests an almost similar amount of both substances, where the experimental details state that much more or the TCS has been used. This finding needs explanation. Finally, in the TEM images also small \"brighter\" particles can be observed in the background. Are those pure OTS networks?\nA more detailed molecular analysis of these 150nm wide objects could have been done by solid state Si-NMR, for example to learn even more about the structure formation.\nThe cited references cover most important literature in the field (Lotus, Salvinia, Springtail, Quéré, Ras, Tuteja, PFAS debate etc.). However, some work is missing, in particular in regard to IPN materials based on Silane-/SiOs networks on textiles (and other surfaces). In a similar fashion, the formation of amorphous silica networks has been recently shown on paper fibers to gain superdrophobic paper surfaces. The authors may consider to implement also such work in their discussion of the state of art. Finally, there exist some patents describing silane-based IPN as a tool to produce superhydrophobic textiles - again, authors could discuss there results in the context of these existing reports.\nI consider the manuscript to be significant in the field, it has particular noteworthy new results and the authors thoroughly investigated the textile-water interactions in multiple settings - very impressive. There are only a very few minor concerns mentioned above that could be addressed by the authors prior to publication.", "reviewer_3": "The authors have presented a method for producing fabrics that exhibit superhydrophobic properties along with high abrasion and impact resistance. It is stated that the fabrics obtained in this study demonstrated outstanding durability against washing, abrasion, and impact conditions. Overall, the manuscript appears to have potential for publication in Nature Communications. However, to enable a more definitive evaluation, additional data should be provided and certain sections should be revised.\n1. The authors claimed that they confirmed the presence of trapped air pockets within the fabric architecture using micro-computed tomography (Micro-CT) analysis. However, this finding is not clearly demonstrated in either the videos provided or the figures. It remains unclear whether the phenomenon of water droplets not penetrating into the fabric gaps truly results from the presence of air pockets or simply from the surface tension of the water. The manuscript does not include any definitive evidence or results that clarify this issue. Furthermore, considering the high air permeability of the fabric, the permanent entrapment of air pockets within its structure is physically debatable. Therefore, the existence of such air pockets should be experimentally verified more clearly.\n2. The production method of the T-shirt shown in Video 3 is not clearly described. It is unclear whether the authors first modified the yarns and then produced the fabric or T-shirt from these modified yarns, or whether they applied a coating onto a pre-existing fabric. This distinction is important in terms of scalability and industrial applicability. Hence, the manuscript should more explicitly describe the production process used—particularly the sequence of yarn modification and subsequent fabric formation.\n3. The authors mainly reported the changes in contact angle in their abrasion tests. However, it should be noted that the key parameter in evaluating the performance of superhydrophobic coatings is the sliding angle. Therefore, presenting data on sliding angles is crucial for accurately assessing the true superhydrophobic behavior of the coating. Nonetheless, it is commendable that the authors carefully designed the abrasion and impact tests and simulated various conditions in detail. However, the information provided on the washing tests using detergent is insufficient. Specifically, details such as the detergent concentration, duration of one washing cycle, washing speed, and comparison with typical washing durations for regular garments should be included. Such information is essential for ensuring the reproducibility of the results and their correlation with practical applications.\n4. The authors should also include a cost analysis of the proposed method. In the textile industry, production cost is a critical factor that directly affects the feasibility and commercialization potential of any technology. Therefore, assessing the impact of the chemicals used, processing durations, and energy consumption on overall production costs is important. Adding a cost analysis would enhance the practical value of the study and more clearly demonstrate the scalability and industrial applicability of the proposed method.\n5. Including data on the toxicity profiles of the silanes used would greatly enhance the scientific reliability and practical significance of the manuscript. In particular, in Video 4, a woman is shown directly wearing the produced T-shirt. This raises concerns about the suitability of the chemicals for skin contact and their potential biocompatibility. Hence, evaluating and discussing the possible toxic effects of the silanes in terms of human health and environmental safety would strengthen the integrity and credibility of the work.\n6. The manuscript does not clearly address whether the treatment process caused any stiffening or changes in the tactile feel of the fabrics. In textile applications, coating or modification processes often affect the flexibility, softness, and tactile comfort of the fabric. Therefore, it is important to assess how the applied method influences the mechanical and sensory properties of the fabric. Providing quantitative or qualitative data—such as bending rigidity, air permeability, or tactile softness (handle)—would enhance the credibility of the study from a textile application standpoint."}, "author_response": "Point-by-Point Response to Reviewers\nDear Editor and Reviewers,\nThank you sincerely for your time and insightful comments on our manuscript. We\nhave thoroughly revised the manuscript in accordance with all suggestions, which has\nsignificantly improved the quality and clarity of our work. Below, we provide a point-\nby-point response to each reviewer’s comments.\nResponses to Referee #1\nIn the manuscript, Z. Liu et al. present a new approach to prepare robust\nsuperhydrophobic textiles. Robustness has been the most important property to be\nachieved for superhydrophobic surfaces. The suggested method is well developed, and\nresults are reliable. In addition, this work would be of general interest to the broader\naudience of Nature Communication. However, for publication, there are some concerns\nto be solved, as below.\nMany thanks.\nComment 1: There are several literatures about textile showing robustness and\nsuperhydrophobicity, such like silicone nanofilament studies, proposed by Stefan\nSeeger group (Universität Zürich Irchel). Authors should compare the properties with\nprevious literatures more thoroughly, which make novelty stronger.\nResponse: We thank the reviewer for raising this important point. The pioneering work\nby Prof. Seeger’s group on superhydrophobic silicone nanofilaments is indeed\nfoundational. We agree that an in-depth literature comparison was needed. We have\nnow revised the Introduction section to include a more detailed comparison with\nprevious robust superhydrophobic coatings on textiles, explicitly citing the relevant\nstudies.\nIn particular, we discuss the durable superhydrophobic fabric coatings developed by\nSeeger and co-workers, highlighting how those silicone nanofilament coatings achieve\nrobustness through physical entanglement on fibers. We contrast this with our MARS\napproach, which forms a covalently bonded network on the fiber surface, and we\nexplain why this molecular-level attachment yields superior abrasion resistance. We\nhave added the following to the Introduction (page 2 and page 8 of the revised\nmanuscript):\n“silicone nanofilament6, 7 coatings or silane-based interpenetrating networks on\nvarious textiles6-8”\n“Compared with previous durable superhydrophobic treatments, such as silicone\nnanofilament coatings6, 7, 39, silica nanoparticles40 and perovskite-silane composite\nfibers8, the covalent bonding of MARS offers a distinct advantage in mechanical\nrobustness. Silicone nanofilaments typically adhere to fibers via physical entanglement\nor physisorption. In contrast, MARS forms a molecularly assembled interpenetrating\nnetwork shell that is chemically grafted to each fiber’s surface (Supplementary Fig. 4).”\nReferences added:\n6. Artus, G. R. J. et al. Silicone nanofilaments and their application as\nsuperhydrophobic coatings. Adv. Mater. 18, 2758-2762 (2006).\n7. Zimmermann, J., Reifler, F. A., Fortunato, G., Gerhardt, L. C. & Seeger, S. A\nsimple, one‐step approach to durable and robust superhydrophobic textiles. Adv.\nFunct. Mater. 18, 3662-3669 (2008).\n8. Tian, T. et al. Large-area waterproof and durable perovskite luminescent textiles.\nNat. Commun. 14, 234 (2023).\nComment 2: In the manuscript, tetrachlorosilane (TCS) and octadecyltrichlorosilane\n(OTS) were used for hydrophobic coating. Can other chemicals, having longer or\nshorter carbon chain be used? I am wondering how they were chosen among various\nsimilar chemicals.\nResponse: We appreciate this insightful question. The combination of TCS and OTS\nwas deliberately chosen based on their distinct hydrolysis reaction kinetics and the\nresulting coating structure. As detailed in Section 2 of the Supplementary Information\n(and illustrated in Supplementary Figs. S2c and S4):\nTCS (SiCl , Tetrachlorosilane): Owing to its small molecular size and low steric\n4\nhindrance, TCS has a significantly lower hydrolysis activation energy (E ) than OTS\na\n(approximately 11.1 kcal/mol lower). Therefore, upon initial exposure to moisture, TCS\nwill hydrolyze and condense preferentially. This rapid reaction forms a dense,\namorphous SiO skeleton that covalently bonds to the fiber’s surface –OH groups,\n2\nproviding a strong, mechanically robust base layer.\nOTS (C H SiCl , Octadecyltrichlorosilane): Due to the significant steric hindrance\n18 37 3\nof its long C alkyl chain, OTS is less reactive and tends to hydrolyze/condense only\n18\nafter most of the TCS has been consumed (i.e., after the SiO skeleton has largely\n2\nformed). Consequently, OTS primarily grafts onto the silica skeleton's surface,\nproviding the low-surface-energy C chains required for superhydrophobicity.\ntechnique. Using a shorter-chain silane (e.g., octyltrichlorosilane, C ) might not provide\n8\na sufficient kinetic differential to form a well-defined core–shell structure. Conversely,\nusing only a long-chain silane, such as OTS, would fail to create a robust SiO sublayer.\nInformation into the main text to make it more prominent to readers.\nIn addition, to directly address the reviewer’s question, we conducted comparative\nexperiments with shorter silane chain lengths. We have supplemented the manuscript’s\ndata (in the Supplementary Information) with contact angle, sliding angle, and low-\nfield NMR results for coatings made using shorter alkyl silanes (e.g., C , C and C\n3 8 18\nchains) — these results are summarized in Figure R1. Figure R1 shows that although\nshort-chain silanes can initially produce high static contact angles and low sliding\nangles (indicating superhydrophobicity), the low-field NMR analysis reveals a critical\ndifference. Due to its greater steric bulk, the C chains from OTS are confined to the\n18\noutermost layer of the coating, whereas shorter chains (C , C and C ) tend to be\n3 8 18\nincorporated into inner portions of the silica network. In other words, short-chain\nsilanes do not form the same distinct core–shell structure. Instead, they intermix more\nhomogeneously, which prevents them from building a comparably robust,\nmechanically durable shell. These findings reinforce why we chose the TCS + OTS\ncombination for an optimal, robust coating.\nFigure R1(related to Supplementary Fig. 6). The superhydrophobic performance of\ndifferent alkyl silanes. a, The contact angle and sliding angle, b, The low-field NMR\nof different alkyl silanes shows that the T2 relaxation times is the shortest when the\nhydrophobic chain is C . c, The signal percentage contents of the three types of\n18\nrelaxation times in the samples, calculated by fitting the low-field NMR data. d, The\nrelaxation time distribution corresponding to samples with different carbon chain\nlengths; a shorter relaxation time indicates a more ordered carbon chain assembly. e,\nSchematic diagram of the structure of self-assembled condensation products of silanes\nwith different initial carbon chain lengths. Based on the low-field NMR T2 relaxation\ntime results, OTS forms a large number of ordered crystalline shell layers of C chains\n18\non the surface of silica particles; the crystallization leads to an extremely short T2\nrelaxation time for these C chains. In contrast, a small amount of C groups inside\n18 18\nthe disordered condensed porous silica cannot form ordered assemblies, thus resulting\nin a longer relaxation time. Compared with C , C has smaller steric hindrance, so more\n18 8\nmixed transition layers are formed in the assembly result, and it cannot effectively\naccumulate on the silica surface. The steric hindrance of the C (TMS-Cl) group is\n3\nalmost the same as that of TCS, so it is basically randomly distributed during the\ncondensation process. *Since TMS does not crystallize at room temperature, the T2\nrelaxation time information of TMS only reflects its bound state and cannot accurately\ndetermine the distribution of the TMS groups themselves on the surface or within the\ninterior.\nComment 3: The carbon chain length and concentrations of chemicals might change\nmechanical property. It would be good to show controlling mechanical property, such\nlike how brittle are they, by varying chemicals and concentrations.\nResponse: The reviewer’s focus on the textile’s mechanical properties (flexibility,\nhand feel) is indeed crucial. We have already quantified these properties using a Fabric\nTouch Tester, and the data are presented in Fig. 3d of the main text and in\nSupplementary Table S2.\nThe Fabric Touch Tester results (radar chart in Fig. 3d) show that our optimized MARS\ncoating (4% TCS / 2 % OTS, as in the manuscript) produces almost no change in key\nhand-feel metrics compared to the untreated control fabric. For example, the bending\naverage rigidity of the MARS-treated fabric is 31.7 gf·mm/rad, versus 31.1 gf·mm/rad\nfor the untreated control (virtually identical). The surface roughness amplitude of the\nMARS-treated fabric is 7.60 µm (lengthwise) and 7.55 µm (widthwise), compared to\n7.41 µm and 7.48 µm for the control, respectively. These minimal differences confirm\nthat our MARS shell is an ultrathin nanoscale coating on individual fibers, not a thick,\nbrittle coating that fills pores or forms a stiff film on the fabric (in stark contrast, the\nCapstone-FS nanoparticle coating did measurably increase fabric stiffness and\nroughness). We have emphasized this advantage of retaining the fabric’s original\nsoftness in the revised main text (see page 8).\nBesides fabric touch test, the wearing performance before and after MARS\nmodification was further assessed by folding and bending tests (Figure R2). All\nsamples were cut into 15 cm × 15 cm specimens and were foldable under their own\nweight. In bending tests, each sample can be naturally bent to 90° before and after\nMARS treatment, indicating that the soft handfeel was effectively preserved.\nOverall, the MARS treatment method maintains the superhydrophobic and wear-\nabrasion properties of the fabric without affecting its inherent softness.\nFigure R2. Folding and bending performance of no treated and MARS\nmodification fabric. a, Floding test, b, Bending test. The dyed blue droplet behavior\non the fabric surface, providing the fabric’s superhydrophobic properties.\nOur modification to the manuscript (On page 9, line 197):\n“We assessed the effect of the MARS coating on the textile’s tactile properties, as\ncoating processes often compromise fabric feel. As shown by quantitative fabric hand\nmeasurements (Fig. 3d and Supplementary Table 2), the MARS-treated fabric is\nvirtually indistinguishable from the untreated control in key haptic metrics such as\nbending rigidity and surface roughness (e.g., 31.7 gf·mm/rad vs. 31.1 for control;\nsurface roughness ~ 7.6 µm vs ~ 7.4 µm for control). This provides strong evidence that\nMARS’s ultrathin coating imparts robust functionality without sacrificing the fabric’s\nnatural softness, drape, or breathability, unlike many conventional coatings that stiffen\nthe textile.”\nComment 4: Robustness was characterized by contact angles. However, I am not sure\nthe structures are really unchanged by only contact angles. The SEM images of the\nstructures have to be characterized after various durability tests applying stress.\nResponse: We agree with the reviewer that visualizing the coating morphology after\ndurability tests is important. In addition to the data already provided (e.g., in Fig. 3f of\nthe original submission, and Supplementary Figs. S12 and S14), we have now further\nsupplemented the manuscript with SEM images of the MARS coating after a variety of\ndurability tests (new Figure R3 in the response, also added to the Supplementary\nInformation).\nIn these new analyses, we examined the surface topography of MARS-treated fabrics\nbefore and after: Martindale abrasion, falling-sand abrasion, tensile (stretching) fatigue,\nscrub (brushing) resistance, peel adhesion tests, walking friction (treadmill test), and\nmultiple wash cycles. In all cases, the MARS-modified fabric maintained its\ncharacteristic nanoscale morphological features post-test. We draw particular attention\nto Supplementary Fig. S13 in the revised manuscript, which presents high-resolution\nSEM images of a MARS-coated canvas after 20,000 Taber abrasion cycles. The SEM\nimages clearly show that, despite some wear to the fiber itself, the MARS-formed\nnanostructured silica shell (see inset of Supplementary Fig. S13) remains firmly\nadhered to the fiber surface and has not delaminated. This provides direct visual\nevidence of the coating’s robustness and integrity after harsh abrasion. We have now\ncited this SEM evidence in the revised main text and added an explicit statement in the\ndescription of Fig. 3b to highlight that the nanostructures persist after testing.\nOur modification to the manuscript: On page 8, line 183 of the revised manuscript, we\nexplicitly note the post-abrasion SEM findings to address this comment:\n“In the Taber test, SEM images (Supplementary Fig. 13, inset) confirm that even after\n20,000 abrasion cycles, the nanostructured MARS shell remains intact on the fiber\nsurface, providing direct visual evidence of the coating’s robustness.”\nWe trust that these additions address the reviewer’s concern by demonstrating that the\nMARS coating’s structure remains in place and effective even under extensive\ndurability testing.\nFigure R3(related to Supplementary Table. 3). Changes in the MARS coating surface\nmorphology after various durability tests. SEM images of MARS-treated fabric\nsamples before and after (a) Martindale abrasion, (b) falling-sand abrasion, (c) tensile\n(stretching) fatigue, (d) scrub brushing, (e) 3M tape peel, (f) treadmill walking friction,\nand (g) multiple launderings. In all cases, the hierarchical silica shell structures remain\nafter testing. For example, in (a), after 80,000 Martindale cycles, the fabric surface\nretains the mushroom-like silica aggregates (inset); in (e), after 500 peel tests, the fiber\nstill shows a silica coating (no bare fiber exposed). These results corroborate that the\nMARS nanostructured shell remains firmly attached and essentially unchanged in\nmorphology despite the applied stresses.\nComment 5: For repellency, dynamic contact angles are more important parameter\nthan static contact angle. Therefore, in addition to SEM images, dynamic contact angles\n(contact angle hysteresis and sliding angle) have to be included.\nResponse: In fact, we did report the initial sliding angles for our pristine MARS fabrics\nin the original manuscript (see page 6, line 128 of the revised main text): the woven and\nknitted MARS fabrics have very low sliding angles of 1.8° and 3.0°, respectively,\nindicating excellent mobility of droplets on the surface.\nFollowing the reviewer’s advice, we have now added sliding angle data after\ndurability tests to the Supplementary Figure 16 (Figure R4). In these new results, we\nmeasured the sliding angle of water droplets on MARS-treated fabrics after key\ndurability tests (e.g., after 20,000 abrasion cycles, after 20 laundry cycles, etc.). The\noutcomes show that the sliding angle remains below 5° even after these rigorous tests,\nconfirming that the surfaces continue to exhibit excellent dynamic water repellency\npost-abuse.\nFigure R4 (related to Supplementary Fig. 16). The sliding angle of fabric before and\nafter durability tests. The sliding angle remains below 5° even after various rigorous\ntests.\nOur modification to the manuscript (see page 10, line 228 of the revised main text):\n“Even after extensive abrasion and washing tests, the treated fabrics retained very low\nsliding angles (<5°), indicating that dynamic water repellency is also preserved\n(Supplementary Fig. 15).”\nThis addition, together with the new data in the SI, addresses the reviewer’s point by\ndemonstrating that not only are the static contact angles high, but the droplets also\nremain highly mobile (low CAH/low sliding angle) even after the fabric has been\nsubjected to wear and laundering.\nResponses to Referee #2\nThe manuscript describes a MARS (molecular-assembled robust-superhydrophobic\nshell) method that works without fluorinated chemicals and covalently binds\nsilica/OTS/TCS networks to fibers to obtain durable superhydrophobic textiles.\nThere are noteworthy results: The specific combination of TCS+OTS in a one-step\nmolecular assembly on a fiber basis is new. In particular, the chemical one-step\nmodification prior to fiber textile-processing. The durability (abrasion, vapor resistance)\nwith simultaneous vapor permeability is also unusual and of further interest, not only\nfor superhydrophobic textiles.\nMany thanks.\nComment 1: The authors report “mushroom-like aggregates” of the IPN, and the\ngeometry of the nanostructures on the fibers has been analyzed by TEM. The authors\nstate that TCS preferentially condenses to form a dense amorphous silica core (dark\narea), while OTS modifies the surface of the amorphous silica. Analysis of the TEM\ndata suggests an almost similar amount of both substances, where the experimental\ndetails state that much more or the TCS has been used. This finding needs explanation.\nFinally, in the TEM images also small \"brighter\" particles can be observed in the\nbackground. Are those pure OTS networks?\nResponse: We thank the reviewer for this detailed observation regarding our TEM\nanalysis. As discussed in our response to Referee #1 (Comment 2 above), the formation\nof the MARS coating is not a homogeneous co-deposition of TCS and OTS, but rather\na sequential (core–shell) assembly. We are happy to clarify the TEM interpretation.\nThe TEM image provided (Supplementary Fig. S5b) shows the final nanostructure on\na fiber. We agree that at first glance, one might interpret the image as indicating\ncomparable amounts of “dark” (SiO from TCS) and “bright” (organosilica from OTS)\n2\nmaterial. However, this is likely a consequence of TEM imaging a 2D projection of a\ncore–shell structure. Based on our kinetic model (see Supplementary Section 2 and Fig.\nS4), TCS (which we feed in larger proportion) reacts first and forms the dense\nsilica core (the darker regions in the TEM), whereas OTS (smaller feed ratio) reacts\nlater and primarily functionalizes the surface, forming a thinner shell (the brighter\nhalo around the particles in TEM).\nWe also note that the so-called re-entrant surface structures and the lower packing\ndensity of the outer layer enhance the shell's brighter appearance. Essentially, the OTS-\nmodified silica on the exterior has a porous, ragged morphology (the “mushroom-like”\ntexture) that traps air, making it less electron-dense and thus brighter in TEM.\nIn summary, the core–shell morphology observed in TEM is entirely consistent with\nour proposed mechanism: TCS forms the structural silica skeleton (core), and OTS later\ngrafts onto its surface (shell). The apparent “similar amounts” in the image do not\ncontradict the chemistry, because the shell (though thin) encases the core and can\noccupy a comparable projected area in 2D.\nTo ensure readers are not confused, we have clarified this explanation in the revised\nmanuscript (Discussion, page 10) and included an annotated schematic of the core–\nshell structure (see Figure R5 in this response, corresponding to Supplementary Fig.\nS5 in the manuscript).\nFigure R5 (related to Supplementary Fig. S5). Silica “mushroom” shells on a fiber\n(core–shell structure). a, SEM image showing the formation of mushroom-like silica\naggregates (~150–170 nm) and nanostructured silica shells (~20–50 nm features) on a\ncotton fiber after MARS treatment. b, TEM image at higher magnification, revealing\nthe core–shell architecture: TCS-derived silica preferentially forms a dense amorphous\ncore (dark region), while OTS-derived organosilica forms a thinner, lighter shell around\nthe core. c, Energy-dispersive X-ray spectroscopy (EDS) mapping of Si, C, and O\nelements on a treated fiber, confirming that silicon (from SiO ) is distributed throughout\n2\nthe coatings and carbon (from OTS) is present predominantly at the outer surfaces. (We\nalso note that the small-molecule TCS can penetrate slightly into the fiber surface,\nwhere it anchors the SiO network, ensuring strong attachment.) These analyses support\n2\nthe core–shell IPN model proposed for the MARS coating.\nComment 2: A more detailed molecular analysis of these 150 nm wide objects could\nhave been done by solid state Si-NMR, for example to learn even more about the\nstructure formation.\nResponse: We thank the reviewer for this insightful suggestion. Following your\nrecommendation, we have carried out a detailed analysis of the 29Si MAS solid-state\nNMR spectrum of the TCS-OTS hybrid material (Figure R6).\nThe spectrum reveals two distinct types of silicon environments, including Q-type\nspecies originating from the silica core and T-type species derived from the\norganosilane shell. The Q4 peak, centered at -113.5 ppm, is attributed to fully condensed\nsilica units (Si(OSi) ). A minor signal at -55.1 ppm corresponds to Q3 species\n4\n(Si(OSi) OH), indicating a small population of residual surface silanols. The shell-\n3\nspecific T3 and T2 peaks appear clearly at -68.4 ppm and –58.6 ppm, respectively,\ncorresponding to covalently bonded organosilicon units R–Si(OSi) and R–Si(OSi) OH\n3 2\nfrom OTS.\nQuantitative peak integration yields the following distribution: Q4: ~60.0%, Q3: ~4.6%,\nT3: ~18.3%, and T2: ~17.1%. This distribution strongly supports the proposed core-\nshell structure. The Q4-rich signal indicates that the TCS precursor forms a highly\ncondensed silica core. The very low Q3 signal suggests that most Si-OH groups have\nreacted with OTS during shell formation. The presence of distinct T3 and T2 signals\nconfirms successful grafting of the organosilane, forming a covalently bonded shell.\nFigure R6. Solid-state 29Si NMR of MARS-coated fibers. The solid-state NMR\nspectrum exhibits broad peaks corresponding to Q2, Q3, and Q4 silicon (typical of a\ncondensed silica network from TCS), as well as T2/T3 silicon (from OTS-grafted sites).\nThe dominance of Q3/Q4 signals confirms extensive Si–O–Si cross-linking (formation\nof an SiO network), while the presence of T-type signals confirms that OTS has been\n2\ncovalently incorporated, likely as end-group sites on the silica. These NMR results\nsupport the core–shell assembly model of the MARS coating.\nWe have incorporated this expanded NMR discussion into the revised Supplementary\nInformation, as per the reviewer’s recommendation. These findings not only reinforce\nthe validity of the core–shell architecture but also provide valuable guidance for future\noptimization, such as maximizing T3 condensation and minimizing unreacted silanols\nto improve shell density and interfacial stability.\nWe sincerely thank the reviewer for this constructive comment, which has helped us\nstrengthen the structural characterization of our material.\nComment 3: The cited references cover most important literature in the field (Lotus,\nSalvinia, Springtail, Quéré, Ras, Tuteja, PFAS debate etc.). However, some work is\nmissing, in particular in regard to IPN materials based on Silane-/SiOs networks on\ntextiles (and other surfaces). In a similar fashion, the formation of amorphous silica\nnetworks has been recently shown on paper fibers to gain superdrophobic paper\nsurfaces. The authors may consider to implement also such work in their discussion of\nthe state of art. Finally, there exist some patents describing silane-based IPN as a tool\nto produce superhydrophobic textiles - again, authors could discuss there results in the\ncontext of these existing reports.\nI consider the manuscript to be significant in the field, it has particular noteworthy new\nresults and the authors thoroughly investigated the textile-water interactions in multiple\nsettings - very impressive. There are only a very few minor concerns mentioned above\nthat could be addressed by the authors prior to publication.\nResponse: We appreciate the reviewer pointing out these omissions. We have now\nconducted an updated literature search and revised the Introduction and Discussion to\nincorporate these important references and provide proper context for previous\nsilane/SiO -network coatings.\nAmorphous silica networks on paper fibers for superhydrophobic paper: e.g., the\nworks by Liu et al. (ACS Nano 2022)49 and Liu et al. (ACS AMI 2024)50, which used\nsilane-based coatings to create superhydrophobic, printable paper surfaces. Also, earlier\nwork by Zhang & Seeger (Angew. Chem. 2011)51 on silicone nanofilaments (an IPN-\nlike structure), achieving ultralow sliding angles.\nSilane modifications on other substrates: e.g., the work by Wang et al. on silane-\ncoupling-agent-modified lithium electrodes (Adv. Mater. 2021)52, which, while in a\ndifferent field, demonstrates the utility of silane networks in improving interfacial\nstability (included for completeness).\nDurable superhydrophobic fabrics using polymeric silanes: e.g., Yu et al. (Appl.\nSurf. Sci. 2018)53, which investigated polymeric silane water-repellent agents on\nfabrics and their effect on durability (one of the few directly related textile studies).\nRelevant patents: e.g., Phelan et al. (US Patent 20200299541A1, 2020)54, which\ndescribes a method for making superhydrophobic coatings on textiles using silanes\n(though with fewer details publicly available).\nWe have added a new paragraph in the Discussion (page 12, line 288 of the revised\nmanuscript) that cites and discusses these works:\n“Silane-based cross-linked networks have been explored on other substrates, such as\npaper49-51, metal electrodes52, and textiles53,54, as well as in patent literature54. However,\nthose studies primarily demonstrated superhydrophobicity without thoroughly\nexamining wear resistance in practical conditions. Our MARS approach, with a well-\ndefined core-shell mushroom-like aggregate structure, yields an IPN shell covalently\nbonded to the fibers, thereby providing high mechanical strength and strong adhesion\nfor other applications.”\nBy including this comparative discussion, we place our work in a more comprehensive\ncontext relative to the state of the art and acknowledge the contributions of these prior\nstudies.\nReferences:\n49. Liu, S. et al. Printable and versatile superhydrophobic paper via a scalable\nnonsolvent armor strategy. ACS Nano 16, 9442–9451 (2022).\n50. Liu, X. et al. Design and synthesis of a robust and multifunctional\nsuperhydrophobic coating with a three-dimensional network structure on a\npaper-based material. ACS Appl. Mater. Interfaces 16, 37111–37121 (2024).\n51. Zhang, J. & Seeger, S. Superoleophobic coatings with ultralow sliding angles\nbased on silicone nanofilaments. Angew. Chem. Int. Ed. 50, 6652–6656 (2011).\n52. Wang, Y. et al. Lithium metal electrode with increased air stability and robust\nsolid electrolyte interphase realized by silane coupling agent modification. Adv.\nMater. 33, 2008133 (2021).\n53. Yu, M. et al. Positive effect of polymeric silane-based water repellent agents on\nthe durability of superhydrophobic fabrics. Appl. Surf. Sci. 450, 492–501 (2018).\n54. Phelan, M., Goff, C., Ward, M. & Thai Trung King, M. Superhydrophobic\ncoatings for the treatment of textiles. U.S. Patent US20200299541A1 (2020).\nResponses to Referee #3\nThe authors have presented a method for producing fabrics that exhibit\nsuperhydrophobic properties along with high abrasion and impact resistance. It is stated\nthat the fabrics obtained in this study demonstrated outstanding durability against\nwashing, abrasion, and impact conditions. Overall, the manuscript appears to have\npotential for publication in Nature Communications. However, to enable a more\ndefinitive evaluation, additional data should be provided and certain sections should be\nrevised.\nMany thanks\nComment 1: The authors claimed that they confirmed the presence of trapped air\npockets within the fabric architecture using micro-computed tomography (Micro-CT)\nanalysis. However, this finding is not clearly demonstrated in either the videos provided\nor the figures. It remains unclear whether the phenomenon of water droplets not\npenetrating into the fabric gaps truly results from the presence of air pockets or simply\nfrom the surface tension of the water. The manuscript does not include any definitive\nevidence or results that clarify this issue. Furthermore, considering the high air\npermeability of the fabric, the permanent entrapment of air pockets within its structure\nis physically debatable. Therefore, the existence of such air pockets should be\nexperimentally verified more clearly.\nResponse: We appreciate this comment. We realize that our wording regarding\n“trapped air pockets” in the fabric was unclear. The purpose of the micro-CT analysis\n(Fig. 1h and Supplementary Movie 2) was to visualize the Cassie–Baxter state, where\nthe stable air layer at the interface between a water droplet and the superhydrophobic\nfabric, rather than to imply permanently trapped air inside the bulk of the fabric.\nWhen a water droplet rests on a MARS-treated textile, it sits in the Cassie state. Most\nof the droplet’s base is supported by air, with the liquid bridging only the tops of the\nfibers. This is why the droplet remains nearly spherical and does not wet the gaps. The\nmicro-CT image clearly shows the droplet (dark region) and a thin air gap beneath it\n(bright region), confirming the presence of an air cushion at the interface. However, we\nagree it was misleading to refer to this as air “within the fabric architecture”. It is more\naccurate to say an air layer at the droplet-fabric interface. Also, this air is not\n“permanently” trapped, it is sustained as long as the droplet remains or as long as the\nfabric is in water. Once the droplet rolls off or the fabric is taken out of water, regular\nair fills the pores again.\nTo clarify, we have revised the wording in the manuscript wherever this was discussed.\nSpecifically, in the Results section (page 6, line 125 of the revised manuscript), we\nchanged the description to:\n“The droplet rests only on the texture tips, with air trapped in the hollows beneath,\nforming a Cassie–Baxter state (Fig. 1h, Supplementary Movie 2).”\nWe no longer talk about “air pockets within the fabric architecture” in a way that\nimplies permanence. We also added a brief explanation in the text that the spherical\nshape of the droplet is due to surface tension and that the fabric is in the Cassie state\n(supported by an air cushion).\nSo, the water droplet’s inability to penetrate is due to surface tension maintaining that\nair layer under the drop (Cassie state). Since our fabric is indeed air-permeable, if you\nwere to force air through it (or immerse it completely), the air in its pores can be\nreplenished (rather than permanently sealed inside). But in dynamic situations (e.g., Fig.\n4h water tunnel tests), we observe that a stable air film can be maintained on the fabric\nsurface under flow, thereby contributing to drag reduction.\nWe hope this clarifies the role of the “air pockets”. They’re an interfacial effect (Cassie\nstate), not permanent entrapment within the fabric bulk. The revised text reflects this\nunderstanding.\nComment 2: The production method of the T-shirt shown in Video 3 is not clearly\ndescribed. It is unclear whether the authors first modified the yarns and then produced\nthe fabric or T-shirt from these modified yarns, or whether they applied a coating onto\na pre-existing fabric. This distinction is important in terms of scalability and industrial\napplicability. Hence, the manuscript should more explicitly describe the production\nprocess used—particularly the sequence of yarn modification and subsequent fabric\nformation.\nResponse: We thank the reviewer for highlighting this point, as it speaks to the\nscalability of our approach. Our method is the former one. We first modify the yarn,\nthen fabricate textiles from the modified yarns. We did indicate this in the original\nsubmission (e.g., page 3, line 70, and page 5, line 113 mention treating fibers/yarns\nbefore textile formation; Supplementary Fig. 1 shows a continuous yarn treatment; and\nSupplementary Fig. 7e shows knitting a glove from treated yarn). However, we agree\nit would be helpful to make this explicit in the main text when referring to the T-shirt\nvideo.\nTo clarify, we have added a sentence in the Methods section under “Superhydrophobic\nFabric Preparation” stating (page 13, line 311 of the revised manuscript):“The T-shirt\nshown in Supplementary Movie 3 was knitted using cotton yarns that were pre-treated\nvia the continuous MARS process by Sinotex SNT-803S (Hi-Tech Group Corporation,\nChina). The detail weaving process was shown in Supplementary Movie 8.”\nWe also note that the fabrications were done in a textile factory setting (one of our\nindustry partners helped with weaving/knitting) in the Acknowledgment.\nComment 3: The authors mainly reported the changes in contact angle in their abrasion\ntests. However, it should be noted that the key parameter in evaluating the performance\nof superhydrophobic coatings is the sliding angle. Therefore, presenting data on sliding\nangles is crucial for accurately assessing the true superhydrophobic behavior of the\ncoating. Nonetheless, it is commendable that the authors carefully designed the abrasion\nand impact tests and simulated various conditions in detail. However, the information\nprovided on the washing tests using detergent is insufficient. Specifically, details such\nas the detergent concentration, duration of one washing cycle, washing speed, and\ncomparison with typical washing durations for regular garments should be included.\nSuch information is essential for ensuring the reproducibility of the results and their\ncorrelation with practical applications.\nResponse: This comment has two parts: (a) provide sliding angle data, and (b) provide\ndetailed washing test parameters.\n(a) Sliding Angle: We agree and have added sliding angle measurements. Initial sliding\nangles (1.8°, 3.0°) were reported in the main text, and we have now also included the\nsliding angles after durability testing in the Supplementary Figure 16 (Figure R4, with\nall results remaining <5°). We explicitly mention in the Discussion that the sliding angle\nremains very low after abrasion and washing, indicating robust dynamic repellency.\nFigure R4 (related to Supplementary Fig. 16). The sliding angle of fabric before and\nafter durability tests. The sliding angle remains below 5° even after various rigorous\ntests.\n(b) Washing Test Details: We realized that our original text only mentioned the\nstandard (AATCC 22 spray test) used to evaluate repellency after washing, but not the\nwashing protocol itself. We have now added the missing details in accordance with the\nAATCC standards for home laundering.\nOur washing procedure followed AATCC LP1-2021 (Laboratory Procedure for Home\nLaundering), using a front-loading washing machine and AATCC Standard Reference\nDetergent per AATCC M1-2017e. We have included all relevant parameters in a new\nSupplementary Table (Table S5).\nTable R1 – Detailed home laundering parameters (per AATCC standards)\nParameter Condition\nWashing machine type High-efficiency front-loading washer\nWash standard AATCC LP1-2021 (Home Laundering)\nAATCC 1993 Standard Reference Detergent\nDetergent\n(per AATCC M1-2017e)\nWater volume (L) 15 ± 4 L (high water level setting)\nLoad weight (fabric) 1.8 ± 0.1 kg\nDetergent amount 50 ± 1 mL\nWash agitation speed 45 ± 10 rpm (rotation)\nWash cycle time 11 ± 1 minutes (normal cycle)\nRinses 2 rinse cycles\nFinal spin speed 1300 ± 150 rpm\nFinal spin duration 12–18 minutes\nWash water temperature 25 ± 3 °C (cold wash)\nUsing the above conditions, we washed our samples for up to 20 cycles and then\nevaluated their water repellency via the AATCC 22 spray test as reported (they retained\nhigh ratings, AATCC 95–100 even after 20 washes).\nWe have added a reference to these details in the Methods section of the manuscript.\nSpecifically, on page 29 of the revised SI, we note that Supplementary Table 4 provides\ndetailed information on the washing parameters. This will ensure reproducibility and\nallow readers to compare our washing conditions to typical home laundry conditions\n(which they indeed mimic).\nComment 4: The authors should also include a cost analysis of the proposed method.\nIn the textile industry, production cost is a critical factor that directly affects the\nfeasibility and commercialization potential of any technology. Therefore, assessing the\nimpact of the chemicals used, processing durations, and energy consumption on overall\nproduction costs is important. Adding a cost analysis would enhance the practical value\nof the study and more clearly demonstrate the scalability and industrial applicability of\nthe proposed method.\nResponse: We agree that a cost and scalability perspective is very important for a\npractical technology. While a complete techno-economic analysis is complex and\nperhaps outside the scope of a single paper, we have taken the reviewer’s suggestion\nand added a qualitative cost assessment to the Discussion section of the revised\nmanuscript.\nOur cost analysis considers the following aspects:\nRaw Material Costs: The key chemicals (TCS and OTS) are commodity silanes. TCS\nis actually an industrial byproduct (of polycrystalline silicon production) and is\nrelatively cheap. We found that in China, 99% TCS is approximately $0.56 USD per\nkg (source: guidechem.com, Shandong province pricing). OTS is more expensive,\naround $9.8 USD per kg for 95% purity. However, it’s used in much smaller quantities\nthan TCS.\nProcess Costs: Our coating process is a one-step dip-and-dry at room temperature. It\ndoes not require any high-temperature curing or specialized energy input (aside from\nrunning a pump and a winding machine, which are low-power). This means energy\nconsumption is low (basically just running the line and perhaps a condenser for solvent\nrecycling).\nSolvent Costs: We use petroleum ether (a light hydrocarbon solvent). It costs around\n$1.0–$1.2 USD per kg. Importantly, in any scaled implementation, this solvent can be\ncaptured and recycled in a near-closed loop (since we condense the evaporated solvent\nafter the coating bath). Solvent recycling can significantly offset solvent costs.\nExample Cost Calculation: We estimated coating ~1 m2 of cotton fabric (~170 g). The\ncost of chemicals (TCS + OTS) and solvent (accounting for typical losses) came to\nroughly $0.27. That extrapolates to about $1.56 per kg of fabric. If we implement ~75%\nsolvent recovery (which is reasonable industrially), we save about $0.30 per kg of fabric\nin solvent cost, bringing the net cost down to ~$0.69 per kg of fabric (i.e., about $0.12\nfor that 170 g piece). These costs are very low in the context of technical textiles. For\nreference, durable water repellent (DWR) fluorochemicals often add several dollars per\nyard of fabric.\nWe summarized these points in the Discussion with quantitative examples. Here is the\nessence of the added text (page 5 of revised manuscript):\n“Based on our estimates, treating a 170 g cotton fabric costs only about $0.27 (roughly\n$1.56 per kg of fabric), which can be reduced to ~$0.12 (∼$0.69 per kg) if ~75% of the\nsolvent is recovered. These factors indicate that the MARS treatment is economically\nfeasible for large-scale manufacturing.”\nComment 5: Including data on the toxicity profiles of the silanes used would greatly\nenhance the scientific reliability and practical significance of the manuscript. In\nparticular, in Video 4, a woman is shown directly wearing the produced T-shirt. This\nraises concerns about the suitability of the chemicals for skin contact and their potential\nbiocompatibility. Hence, evaluating and discussing the possible toxic effects of the\nsilanes in terms of human health and environmental safety would strengthen the\nintegrity and credibility of the work.\nResponse: The safety of the final product is paramount, especially since our goal is to\nuse these fabrics in wearable applications, and we emphasize the PFAS-free aspect as\na health/environment benefit.\nWe want to clarify that after the MARS treatment, the final chemical composition on\nthe fiber is a covalently bonded silica (SiO ) network with grafted long-chain\n2\nhydrocarbons (C ). In other words, once the coating is formed, there are no free silanes\n18\nleft. They have hydrolyzed and condensed into a solid silica structure, and the reactive\nchlorines are long gone (they form HCl, which is neutralized in the process). So, the\ncoated fabric is essentially fiber + silica + a wax-like hydrocarbon coating.\nSilica (in the form of amorphous SiO ) is generally regarded as safe/inert (it’s basically\n2\nlike sand or glass, both of which are benign in clothing), and long-chain alkanes are\nsimilarly inert (paraffin waxes are even used in cosmetics and food packaging). So\nchemically, we expect the coating to be non-toxic and biocompatible.\nTo substantiate this, we conducted a cytotoxicity and cell proliferation assay using NIH\n3T3 fibroblast cells. We incubated cell cultures with fabric sample extracts (to simulate\nleachable substances) and directly with tiny fabric specimens, and measured cell\nviability over 5 days using the CCK-8 assay (a standard cell metabolic activity assay).\nWe compared untreated control fabric, MARS-coated fabric, and fabric treated with a\nfluorinated water-repellent (Capstone-FS, which contains PFOS). The results were\nquite clear. Control (untreated) and MARS-treated fabrics showed no significant\ndifference in cell viability or proliferation over 5 days. The cells in both cases\nproliferated normally (almost overlapping growth curves). Capstone-FS-treated fabric,\non the other hand, showed substantial cytotoxic effects. By Day 5, the cell count\n(viability) was only about 50% of that in the control/MARS groups. This suggests that\nPFOS or its byproducts leaching from that fabric inhibited cell growth (which aligns\nwith the known toxicity of PFAS compounds). These results (shown in Figure R7 in\nthe response and added to the Supplementary Info of the manuscript) indicate that our\nMARS coating has no adverse effect on cells. In contrast, a conventional PFAS-based\ncoating does have a toxic effect.\nWe have now added a discussion of this “material safety profile” to the manuscript\n(Discussion section). We explicitly note that the coating is analogous to silica and wax\n(both safe) and report that our cell assay showed no cytotoxicity with MARS vs. clear\ncytotoxicity with PFAS.\nIn terms of environmental safety, the coating is comprised of elements (Si, C, O, H)\nthat should not pose persistence or bioaccumulation issues. Unlike PFAS, this was a\nmajor motivation for this work.\nSpecifically, the manuscript now includes on page 12:\n“Material Safety: The coating’s safety is our final concern. MARS-treated fiber is\ncoated with a fully hydrolyzed, cross-linked amorphous silicon network functionalized\nwith octadecyl groups. Chemically, this structure is analogous to silica (sand/glass)\ncombined with long-chain paraffin wax—materials that are widely regarded as inert,\nnon-toxic, and biocompatible. We conducted cytotoxicity and cell proliferation assays\n(5-day CCK-8 test using NIH 3T3 fibroblasts) to evaluate the MARS coating’s safety\n(Supplementary Fig. 21). The results showed no significant difference in cell viability\nor growth between the MARS-coated fabric and an untreated control. In contrast, a\nfabric treated with a PFAS-based water repellent (Capstone-FS, containing PFOS)\nexhibited only about half the viable cell count of the other two groups by day 5. These\nfindings indicate that our fluorine-free MARS treatment has no detectable adverse\neffect on cell growth, underscoring a substantial safety advantage over conventional\nperfluorinated coatings.”\nFigure R7 (Supplementary Fig. 21). Cytotoxicity and cell proliferation assay of\nsuperhydrophobic fabric extracts. a, CCK-8 cell proliferation results over 5 days,\nexpressed as a percentage of the Day 1 control. The control (gray) and MARS (green)\nsamples support robust cell growth (nearly doubling by Day 5), while the Capstone-FS\n(blue) causes significantly reduced cell proliferation (only ~50% of control by Day 5).\nError bars represent standard deviation (n = 3). These results demonstrate that the\nMARS coating is non-toxic to mammalian cells, in contrast to the fluorinated coating,\nwhich shows considerable cytotoxicity. b, Fluorescence microscopy images\n(Live/Dead staining) of NIH 3T3 fibroblast cells after 24 hours incubation with extracts\nfrom untreated control fabric, MARS-treated fabric, and PFAS-treated (Capstone-FS)\nfabric. Live cells fluoresce green; dead cells (if any) would appear red. The control and\nMARS groups show confluent layers of healthy fibroblasts, whereas the Capstone-FS\ngroup has fewer cells.\nComment 6: The manuscript does not clearly address whether the treatment process\ncaused any stiffening or changes in the tactile feel of the fabrics. In textile applications,\ncoating or modification processes often affect the flexibility, softness, and tactile\ncomfort of the fabric. Therefore, it is important to assess how the applied method\ninfluences the mechanical and sensory properties of the fabric. Providing quantitative\nor qualitative data—such as bending rigidity, air permeability, or tactile softness\n(handle)—would enhance the credibility of the study from a textile application\nstandpoint.\nResponse: We have, in fact, performed quantitative evaluations of the fabric’s\nmechanical and sensory properties using a Fabric Touch Tester, which measures\nparameters like bending rigidity, surface roughness, etc.. The MARS-treated fabric is\nalmost indistinguishable from the untreated fabric in terms of flexibility and softness.\nWe summarize the completeness: Bending rigidity (one indicator of stiffness): MARS\n= 31.7 gf·mm/rad, Control = 31.1 gf·mm/rad (virtually no change). Surface roughness:\nMARS ~7.6 µm, Control ~7.4 µm (a difference of only ~0.1–0.2 µm, which is\nnegligible and not perceptible to touch). Air permeability was also tested (we mention\nin Discussion: at least 13.5 hours of maintained breathability in one test, which basically\nmeans no clogging effect). We included these data in Fig. 3d and Supplementary Table\nS2 of the manuscript, and we have now emphasized in multiple places that MARS does\nnot cause stiffening or loss of comfort.\nOur modification to the manuscript (On page 9, line 202):\n“This provides strong evidence that MARS’s ultrathin coating imparts robust\nfunctionality without sacrificing the fabric’s natural softness, drape, or breathability,\nunlike many conventional coatings that stiffen the textile.”\nIn summary, we have now explicitly stated in the paper that the MARS treatment has\nminimal impact on tactile feel, a finding that has been quantitatively confirmed. Thus,\na garment treated with MARS remains just as soft and wearable as before treatment –\nan important validation for real-world use.\nLastly, we thank all the reviewers once again for their constructive and valuable\nfeedback. The manuscript is much stronger after addressing these points, with clearer\nexplanations, additional data (comparative literature, dynamic angles, washing details,\ncost, toxicity, etc.), and improved context. We hope our revisions meet with your\napproval."}, {"round": 2, "reviewer_comments": {"reviewer_1": "From my side, all concerns have been solved. In my opinion, it has now good enough quality to be published in top journal Nature Communications.", "reviewer_2": "The authors have addressed in an excellent fashion all raised comments and suggestions. In particular, additional experiments have been conducted and results included., Given this thourough revision, I believe that the manuscript is acceptable for publication in nature communications in the present form."}, "author_response": ""}]

Decision letter