Stretch-induced reversible self-growth of high aspect ratio microstructures scribed by femtosecond laser

Domain: chemistry
Published: 2026-03-04
Editorial outcome: minor_revision

Abstract
Inspired by the intricate surface patterns in nature, the concept of polymer self-growth has recently been applied to construct synthetic structures. However, existing techniques, whether driven by chemical reactions or physical mass transport, fail to offer rapid and reversible tuning, and typically can only produce structures with low aspect ratios. Here, we present a generalized stretch-induced polymer self-growth (SIPS) method for reversibly constructing structures on a wide range of pre-stretched elastic membranes, including silicone, PU, PDMS, dielectric elastomer (VHB), and hydrogel. High aspect ratio (~1.4, much larger than the previously reported value ~0.25) straight and bent micropillars with different cross-sections are facilely fabricated by femtosecond laser cutting. By releasing and subsequent re-stretching the membrane, tuning of the grown structures is readily achievable, enabling a rapid (~30 s) and reversible transition between structured and flat surface. Experimental and simulation results confirm that the micropillar height is governed by the stretch ratio and laser scribing depth. The high aspect ratio enhances tactile perception and allows directional bending for encoding information. These capabilities are demonstrated through proof-of-concept applications in Braille training and information encryption/decryption. The presented SIPS method that combines femtosecond laser cutting and the stretching of elastic membranes, offers an efficient approach for fabricating tunable functional microstructures with great potential in the fields of micro/nanofabrication and adaptive surface engineering.

Introduction
Organisms in nature have evolved unique micro- and nanostructures that can reversibly change their shapes, enabling functions such as switchable friction1–3, reversible adhesion4–6, and adaptive camouflage7–9. Such intriguing microstructures are spontaneously formed through a growth mode, where living creatures absorb nutrients and integrate them into their bodies. Inspired by these natural patterns, artificial structures are typically fabricated using subtractive or additive methods, including cutting10, molding11,12, and printing13. While these patterning technologies offer high-fidelity processing capabilities, challenges such as tool wear, damage to the mold, and the necessity for harmful substances limit their sustainability. Moreover, the fabricated structures usually have fixed morphologies, making it difficult to meet the requirements of tunable function.

Inspired by dynamic and nonequilibrium systems in nature14,15, researchers have recently developed chemically driven polymer self-growth to construct synthetic microstructures16–26. For instance, Cui et al. reported a UV light-regulated method that couples photolysis, photopolymerization, and transesterification to drive nutrient solutions into the irradiated region, where they polymerize and form microprotrusions16. Such chemically driven polymer self-growth strategies have greatly advanced micropatterning technologies, with demonstrated applications in structural color27, biomedical implant28, and hydrogel sensors29. However, these methods share several intrinsic limitations: (1) They require complex chemical compounds, such as photoresponsive polymers, polymerizable substances, and harmful solvents or reactants, which lead to multi-step pre-treatment processes and strict reaction conditions. (2) The growth rates are extremely slow, constrained by both the kinetics of the chemical reactions and the diffusion rates of the involved compounds, with average speeds ranging from tens of nm/s to several μm/s16–22. In addition, although several studies17,20 have reported reversible control over the grown structures, these approaches remain limited by slow tuning speeds, reliance on specific materials, and stringent conditions. (3) Structures are limited to straight microprotrusions with a low aspect ratio (<0.3) due to the constraint imposed by the substrate, making it even more challenging to achieve the bending of microstructures. A detailed comparison is provided in Table S1.

As an alternative to chemical approaches, our group developed a physical mass transport-based method termed laser-induced polymer self-growth (LIPS)30,31. Utilizing this approach, micropillars and mushroom-like reentrant microstructures can spontaneously grow from a heat shrinkable shape memory polystyrene membrane. However, LIPS is only applicable to shape memory polymers, and the resulting structures cannot be reversibly tuned, which limits its applications. Therefore, developing a simple and general method to achieve fast and reversible tuning of self-grown structures with high aspect ratio remains a significant challenge.

Here, we report a strategy termed stretch-induced polymer self-growth (SIPS), which enables rapid and reversible fabrication of high aspect ratio structures on various elastic membranes. By precisely controlling femtosecond laser scribing to locally release stress, both symmetrical and asymmetrical polymer growth can be initiated, enabling the fabrication of straight and bent micropillars. The resulting structures achieve aspect ratios up to 1.4. The micropillar height is governed by the stretching ratio and laser scribing depth, and the growth speed reaches 130 μm/s, which is two orders of magnitude faster than that of chemically driven self-growth methods16–22. Upon releasing and re-stretching the membrane, the height, spacing, and bending angle of the grown micropillars can be facilely tuned, allowing for the rapid and reversible tuning between structured and flat surfaces. Micropillar growth, bending, and morphological evolution under cyclic releasing and stretching are systematically studied, and the simulation results exhibit excellent agreement with experimental observations. As a proof-of-concept, the tunable high-aspect-ratio structures are applied to Braille training and information encryption/decryption. The proposed method is general and compatible with various elastic membranes, including silicone, PU, and PDMS, and offers a versatile platform for constructing tunable surfaces in micro/nanofabrication technologies.

Results
Mechanism of stretch-induced polymer self-growth (SIPS)
As shown in Fig. 1a, a commercially available silicone membrane is first cut into a symmetrical cruciform shape and biaxially stretched by 30 mm in both directions to introduce a stretching ratio of λ=1.67 (Video S1 and Fig. S2). A femtosecond laser is then used to ablate the membrane along the 2D circular paths. During laser scribing, a 3D micropillar grows out of the flat surface at a speed of ~130 μm/s (Video S2). Notably, the SIPS-fabricated micropillars exhibit a maximum aspect ratio of 1.4, which is higher than those produced by chemically driven self-growth techniques16–22. When the applied stress is released, the micropillars gradually disappear into the membrane. The detailed reversible self-growth process is demonstrated with schematics, simulations, and experiments in Fig. 1b and Video S3. The simulation confirms that the stress is uniformly distributed in the central region of the stretched membrane (Fig. S3). Laser ablation causes localized separation of material from the surrounding matrix in the x-y plane, which releases stress and induces centripetal shrinkage toward the center, leading to the formation of a micropillar (Fig. S4). The microscope images of a micropillar with increasing laser scribing depth (H 2) demonstrate the self-growth process, and the simulations align well with the experimental results (Fig. S5). Upon gradual relaxation to λ=1, the matrix material surrounding the micropillar recovers to its original thickness, making the micropillar appear embedded within the substrate and restoring the surface to a flat state. Reapplying the stress allows the micropillar to be reversibly formed again (Video S4). Analyses of the radial stress distribution (Fig. 1c and Fig. S6) and cross-sectional profile (Fig. 1d and Fig. S6) from the simulation results show that as H 2 increases from 0 to 166 μm, internal stress within the scribed region gradually decreases to zero, while its height (H 1) increases, resulting in well-defined micropillar.

Compared to our previously reported LIPS method, which is limited to heat shrinkable shape memory polymers30,31 and irreversible structures, the SIPS method enables reversible structural tuning and is applicable to various elastic materials, including Polyurethane (PU), Polydimethylsiloxane (PDMS), Dragon Skin 10 silicone elastomer mixed with carbon nanotubes, dielectric elastomer (VHB) and hydrogel (Fig. S7–8). Moreover, owing to its athermal nature, SIPS achieves finer features with diameters down to 15 μm, significantly smaller than the 150 μm minimum feature size achievable with LIPS (Fig. S9). While one report has demonstrated a chemical self-growth feature size as small as 0.75 μm17, the vast majority of chemical self-growth methods typically produce structures within the 100–500 μm range16,18,20–22. In contrast, SIPS enables rapid, reversible fabrication of high-aspect-ratio structures with fine feature sizes (~15 μm) using standard elastomers without chemical pretreatment, expanding its potential for precise and scalable microfabrication.

Stretch-induced self-growth of straight micropillars
The formation process of the micropillar is investigated by using femtosecond laser to continuously scribe along a circular path with a diameter of 360 μm (Fig. 2a). The number of laser scanning cycles is varied from 0 to 80, increasing the scribing depth (H 2) from 0 to 166 μm. SEM images show the evolution of the micropillars and the large-scale micropillar arrays (Fig. S10). Corresponding cross-sectional profiles of the structures (Fig. 2b) show that the micropillars have sharp sidewalls, with a taper ratio as low as 0.098. Based on morphological changes, the evolution process of the micropillar is divided into four stages. In the first stage (H 2<18 μm), the interior of the circular region remains flat. In the second stage (H 2 ranging from 18 to 38 μm), the material near the scribing path contracts inward, while the central region remains flat, forming an inversed-bowl-shaped structure. In this stage, the structure is still within the matrix. In the third stage (H 2 ranging from 38 to 54 μm), the structure begins to protrude from the flat surface, with the material in the central region being lower than the periphery, forming a crater-like shape. In the fourth stage (H 2>54 μm), the top central part of the structure reaches the same height as the periphery, forming a micropillar. As the laser ablation continues, more material contracts toward the center, and the micropillar grows higher. Quantitative analysis from the confocal cross-sectional profiles and simulation results reveals that as H 2 increases, the diameter of the microstructure (D) decreases from 300 to 220 μm and then stabilizes, while the height (H 1) increases up to 232 μm (Fig. 2c). After complete release of the membrane stress (Fig. 2d), only small bumps remain on the surface, corresponding height profile and sizes are shown Fig. 2e, f, respectively. The maximum height of the bump is ~7.7 μm at 80 cycles, and the diameters are nearly unchanged. Benefiting from the flexibility of femtosecond laser processing, various 2D geometries, such as square and heart shapes, are utilized to fabricate micropillars with diverse shapes (Fig. S11).

To quantitatively investigate how the stretching ratio (λ) and laser scribing depth (H 2) influence micropillar morphology, the self-growth process is simulated under various combinations of λ and H 2. Contour maps of the H 1 and D are obtained by measuring the sizes of the simulated self-grown micropillars (Fig. 2g, h). Experimental results under five representative conditions (H 2=60 μm, λ=1.18; H 2=80 μm, λ=1.27; H 2=100 μm, λ=1.34; H 2=120 μm, λ=1.54; H 2=140 μm, λ=1.67) show excellent agreement with the simulations (Fig. 2i, j). This consistency confirms the predictive capability of the simulation framework and highlights its utility in guiding structural design, thereby reducing the need for laborious experiments and characterizations.

Given the near-zero taper ratio (0.098), the micropillars are approximated as cylinders. Considering the volume of the material is conserved during self-growth, the height of the micropillars H 1 is found to be proportional to λ²−1 and H 2 (Fig. S12). By extracting data from the contour maps, the quantitative relationship between H 1 and λ at different H 2 (Fig. 2k), as well as the quantitative relationship between H 1 and H 2 at different λ are obtained (Fig. S13). We find that the relationship can be fitted by the equation H 1=(λ²−1)(H 2-28). This indicates that structure protrusion occurs only when λ>1 and H 2 exceeds 28 μm (for a scribing diameter of 360 μm), and the H 1 is proportional to both the λ²−1 and H 2, which is consistent with the theoretical prediction (Fig. S12).

Additionally, by extracting data from the contour maps, the quantitative relationship between diameter of micropillar D and λ at different H 2 (Fig. 2l), as well as the quantitative relationship between D and H 2 at different λ are also obtained (Fig. S13). The results show that under the same scribing depth, increasing λ leads to a reduction in D. Similarly, as the H 2 increases, the D gradually decreases and eventually stabilizes. The final stabilized D value is inversely proportional to the λ. Moreover, FEA and experimental results show that varying the Young’s modulus (E) across a wide range has no effect on the self-grown micropillar dimensions (Fig. S14-15). This observation confirms that the micropillar morphology is governed by the pre-stretch ratio and laser scribing depth, and is irrelevant with the material stiffness.

The accessible stretching ratio λ in SIPS is constrained by the mechanical properties of the elastomeric substrate. First, the fracture elongation (F) defines an upper limit, since λ must remain below the fracture strain to avoid macroscopic failure (Fig. S16). The measured elongations at break are approximately 275% for silicone, 500% for PU, and 125% for PDMS, corresponding to maximum stretch ratios of λ≈3.75, 6.0, and 2.25, respectively. Second, the effective stretching ratio accessible for SIPS is governed by the deformation regime of the material. Unlike metals, elastomers do not exhibit a distinct yield point and instead undergo a continuous transition from elastic-dominated deformation to viscoelastic dissipation at large strains32, which is reflected in the strain-dependent slope (tangent modulus) of the stress–strain curves33.

Silicone exhibits a smooth stress–strain response with only modest variation in tangent modulus over a wide strain range, indicating predominantly elastic-dominated deformation (Fig. S16). In contrast, PU shows a reduction in tangent modulus at intermediate-to-large strains due to dissipation-dominated deformation, as reported for polyurethanes34. PDMS exhibits a pronounced increase in tangent modulus at large strains due to strain hardening associated with finite chain extensibility, consistent with established constitutive models of rubber elasticity35. When yield-like deformation in PU and PDMS becomes significant, part of the applied stretching may become irreversible, which can compromise the reversibility of the self-grown microstructures and hinder complete retraction of the micropillars into the substrate upon release. Owing to its predominantly elastic-dominated response, silicone is therefore a favorable substrate for SIPS-induced self-growth.

Reversible tuning of stretch-induced self-grown straight micropillars
To investigate the tuning behavior of micropillars during release and re-stretching, a row of micropillars fabricated at different laser scribing depths (H 2=69, 85, 119 and 127 μm) under a stretching ratio (λ) of 1.67 is subjected to cyclic deformation. Side-view images captured during gradual relaxation from λ=1.67 to 1 reveal a progressive decrease in pillar height (Fig. 3a, Fig. S17), which is consistent with simulation results. As shown in Fig. 3b, for the micropillar fabricated at H 2=127 μm, the H 1 decreases from 180 to 32 μm as λ is reduced from 1.67 to 1.098. The other three micropillars fabricated at H 2 of 69, 85 and 119 μm exhibit the same trend of H 1 reduction during release. Upon reapplying equibiaxial stretching to the membrane, the micropillars exhibit a noticeable increase in height compared to their post-release state (Fig. 3c). This increase occurs primarily during the first re-stretching cycle, which is attributed to localized geometric discontinuities introduced by prior laser scribing. The scribed grooves act as mechanically compliant regions that deform more readily than surrounding material (Fig. S6), leading to tearing and expansion of both groove depth and width (Fig. S18). In subsequent stretching–release cycles, the micropillar height remains unchanged, indicating that the structure reaches a mechanically stable configuration, as further confirmed by the additional cyclic durability results shown in Fig. S19.

As the pre-stretch ratio decreases from 1.67 to 1.098, the spacing between adjacent micropillars reduces from 805 to 497 μm (Fig. 3d). Notably, the micropillar spacing remains constant throughout all stretching–release cycles (Fig. 3e), confirming the geometric reversibility and mechanical stability of the self-grown micropillars.

Stretch-induced self-growth and reversible tuning of bent micropillars
In addition to the straight micropillars, bent micropillars can be fabricated using an asymmetric laser scribing strategy (Video S5). As shown in the schematic and simulation results (Fig. 4a and Video S6), a straight micropillar is first prepared with H 2 of 105 μm, and then a semicircular path is scribed repeatedly on one side of the micropillar with an additional laser scribing depth of H 3, introducing asymmetric stress release. This localized imbalance causes the asymmetric growth, with the micropillar bending towards the other side that is not scanned. A variety of ordered patterns composed of bent micropillars with controlled pillar numbers, spatial arrangements, and bending directions are successfully fabricated (Fig. S20). By releasing the silicone membrane, the bent micropillars retract into the matrix. When re-stretched, the bent micropillars reappear on the surface, demonstrating reversibility (Video S7). The radial stress distributions of the bent micropillars are obtained from simulation results (Fig. 4b and Fig. S21). A comparison of stresses at the left and right roots of the bent micropillar confirm that bending is driven by asymmetric stress release (Fig. 4c). A series of bent micropillars is fabricated with increasing H 3 (Fig. 4d), and cross-sectional profiles show that the bending angle (α) increases with the H 3 (Fig. 4e). After full stress release, only small bumps remain (Fig. 4f, g), with the height and diameter of ~4 μm and ~205 μm, respectively. Reapplying the same stretching ratio to the membrane, the micropillars reappear with the same bending trend as before (Fig. S22). The simulated profiles of bent micropillars with increasing H 3 show the same increasing bending angle as observed with experiments (Fig. 4h). The quantitative relationship between H 3 and both bending angle and length (L) of the micropillars are shown in Fig. 4i. As H 3 increases, the bending angle rises from 90° to 122°, while the length extends from 141 μm to 266 μm. These trends confirm excellent agreement between simulations and experiments.

The tuning behavior of bent micropillars during release and re-stretching is further investigated. A row of bent micropillars, initially fabricated with a H 2 of 105 μm to prepare straight micropillars, is further processed with H 3 of 0, 26, 50 and 79 μm. These are designated as B-0, B-26, B-50 and B-79, respectively. After being subjected to release and re-stretching cycles, side-view images at different stretching ratios are shown in Fig. S23. As λ decreases from 1.67 to 1.098, all bent micropillars exhibit reduced bending angles and tend to become straight (Fig. 4j). Upon re-stretching to λ=1.67, B-0 remains straight, while B-26 and B-50 exhibit increased bending angles (Fig. S23). This behavior is attributed to the aforementioned localized tearing at the laser-scribed microgrooves. In contrast, B-79 shows a slight decrease in bending angle from 116.9° to 113.7°, likely due to the large H 3 making it more sensitive to deformation disturbances. Correspondingly, for B-0, B-26, B-50 and B-79, their lengths decrease during relaxation (Fig. 4k). In subsequent nine releasing-stretching cycles, B-0 remains straight, while the bending angles of B-26 and B-50 increase during the first seven cycles before reaching a plateau (Fig. 4l). For B-79, the bending angle decreases over the initial five cycles and then stabilizes. Correspondingly, the lengths of all micropillars increase during the first three cycles and subsequently remain constant (Fig. 4m). These trends are further confirmed by extended cyclic stretching–release tests up to 1000 cycles, as shown in Fig. S24. These results demonstrate that the morphology of the bent pillars can be reversibly tuned by controlling the stretching ratio. Additionally, smaller H 3 values are associated with improved recovery and mechanical reversibility.

In-situ micro-object capturing and releasing
The potential application of the SIPS method in in-situ micro-object capture and release is demonstrated. As shown in Fig. S25 and Video S8, a claw-like structure composed of four inward-bending micropillars is fabricated around a SiO₂ microsphere, and the claw grasps the microsphere tightly. When air is blown using a rubber suction bulb, the microsphere captured by the claw-like structure remains immobile, whereas nearby unconstrained microspheres are easily removed. This indicates that the claw-like structure provides effective mechanical confinement and can resist external disturbance. By releasing the stress, the micro-claw gradually opens and finally hides in the matrix, thereby releasing the microsphere. Furthermore, an array of such micro-claws is fabricated to simultaneously capture and release four microspheres (Fig. S26), demonstrating the scalability and programmability of this approach for micro-object manipulation.

Tunable Braille for beginning learners
Another potential application of the SIPS method is to assist beginners in learning and practicing Braille, a challenging and time-consuming process where any support should be seized upon. Braille is a widely used tactile writing system for people who are blind or visually impaired. Each Braille character is based on a 3×2 matrix, known as a Braille cell, composed of six dots that may either protrude or remain flat, resulting in 64 possible combinations. Previous studies suggest that enlarged Braille characters can help blind children transition into standard Braille more effectively36,37. However, the fixed dot size and spacing in current enlarged Braille may hinder a smooth transition, especially for beginners. This issue is particularly pronounced for individuals who acquire visual impairments later in life due to injury, illness, or aging. Their reduced fingertip sensitivity, compared to those born blind, makes Braille learning more difficult and discouraging, potentially undermining their learning motivation and confidence. To address these challenges, previous efforts have explored enlarged or tunable Braille devices, but these approaches still have significant limitations. For example, mechanically adjustable Braille displays can modify dot spacing by manually sliding a cover with preset hole arrays of different pitches, and adjust dot diameter by replacing point caps of varying sizes. However, these devices cannot adjust dot height, require manual intervention to change sizes, and typically display only a single character, greatly limiting training efficiency and user convenience37. Dynamic tactile displays with piezoelectric arrays support mode switching but offer only discrete, preset size options without continuous tuning, have fixed dot heights, and involve bulky and expensive setups unsuitable for everyday learning environments38. To date, no system enables simultaneous, continuous, and reversible adjustment of both dot height and spacing within a portable platform.

To overcome this limitation, we have developed a tunable Braille learning platform based on the SIPS method, which allows simultaneous and continuous adjustment of both dot pitch and dot height simply by stretching or releasing a silicone membrane. As illustrated in Fig. 5a, four Braille cells composed of micropillars are fabricated by SIPS method under a stretching ratio of 1.67. The Braille pattern represents the Chinese character “Ke Xue”, meaning “Science”. The design diameter of the circle is 1 mm, and the spacing is 2 mm. The resulting micropillars have a diameter of 510 μm and a height of 716 μm (aspect ratio ~1.4; Fig. S27). The high aspect ratio enhances tactile perception and improves Braille recognition accuracy, especially for beginners or individuals with reduced sensitivity. The micropillars remain intact after repeated finger contact under a normal force of 0.6 N (Video S9). A tactile recognition test is conducted with four first-grade and seven second-grade students from a special education school (Fig. 5b, c). Each student begins by touching the Braille at a low stretching ratio of 1.098. If they are unable to recognize the Braille, the stretching ratio is gradually increased until correct recognition is achieved, which is recorded as the critical recognition stretching ratio. Owing to individual differences in Braille learning duration and tactile sensitivity, the critical recognition stretching ratio varies among students (Fig. 5c). Notably, two first-grade students fail to recognize the Braille even at the maximum stretching ratio of 1.67, while one second-grade student successfully identified it at 1.098, indicating superior tactile perception. The experimental results suggest that the tunable Braille platform can be used to assess the proficiency of learners in Braille. In the future, this platform may assist Braille beginners by starting with an “easy mode” at higher stretching ratio, where enlarged dot spacing and height enhance tactile perception and build confidence. The stretching ratio can then be gradually reduced to help learners adapt to standard Braille, potentially accelerating the learning process (Fig. 5d). In addition, once the stress is completely released, the micropillars retract into the matrix, facilitating damage-free long-term storage and transportation.

To evaluate durability under practical operating conditions, we investigated the fatigue behavior of the Braille micropillar structures under two representative loading modes: repeated stretching–release cycles and repeated tactile contact (touching/friction) cycles. In stretching–release tests, the Braille-patterned membrane was subjected to 0–1000 cycles, and the scribing depth, micropillar height, diameter, and interpillar spacing were quantified (Fig. S28). During the first 200 cycles, minor material tearing at the laser-scribed grooves led to an increase in groove depth, accompanied by a corresponding increase in micropillar height, while the diameter and interpillar spacing remained essentially unchanged. Beyond 200 cycles, all geometric parameters reached a stable plateau and remained unchanged up to 1000 cycles.

To better emulate realistic Braille reading, cyclic tactile tests were performed using a custom-built friction platform (Fig. S29). A Dragon Skin 10 elastomer probe with a hemispherical radius of 8 mm was used to approximate fingertip geometry and compliance, and a normal load of 0.6 N was applied, consistent with reported Braille reading forces39. The sample was subjected to reciprocating friction along a fixed direction, with the sample rotated by 90° after each friction cycle. This procedure was repeated for up to 2000 cycles. During tactile cycling, the scribing depth gradually decreased as a result of substrate thinning induced by friction, while the micropillar height continuously increased from approximately 500 to 800 μm due to repeated compression and stretching imposed by the abrasion head. The micropillar diameter and the interpillar spacing remained unchanged throughout the entire process.

Overall, the Braille microstructures maintain a stable spatial arrangement and structural integrity under both cyclic stretching and repeated tactile loading, with no evidence of catastrophic fatigue within the tested ranges. Notably, repeated stretching–release cycles result in a modest increase in micropillar aspect ratio, while tactile loading induces a more pronounced increase, with the aspect ratio rising from ~0.94 to ~1.43. This behavior is enabled by the compliant deformation of the elastomeric micropillars, which accommodate repeated mechanical interactions through reversible bending and compression rather than material damage. As a result, the evolution toward higher-aspect-ratio Braille features is favorable for tactile perception, indicating that repeated use within the tested cycle range does not lead to functional degradation of the Braille training platform. It should be noted, however, that under much longer-term use involving tens or hundreds of thousands of tactile cycles, wear and material degradation of elastomeric substrates are expected to become unavoidable.

Information encryption and decryption
Beyond tactile applications, high-aspect-ratio micropillars allow information to be encoded through their bending orientations, as demonstrated by a modified Morse code scheme. The phrase “laser-induced polymer self-growing” is encoded using four distinct bending directions—upward, leftward, downward, and rightward—corresponding to dot, dash, double-dot, and double-dash, respectively (Table S30). Straight micropillars serve as delimiters between characters. At a stretching ratio of 1.67, the encoded message is clearly readable (Fig. 5e); when released to λ=1, the micropillars retract and only laser ablation traces remain visible, effectively encrypting the information (Fig. 5f). This encryption–decryption process is shown to be reversible and repeatable over ten full stretching–release cycles (Video S10), confirming the robustness and reusability of the reconfigurable encoding platform.

Discussion
In summary, we propose a generalized and efficient stretch-induced polymer self-growth (SIPS) method for fabricating reversible microstructures on various elastic membranes. The approach demonstrates excellent material adaptability, allowing its application to diverse substrates including silicone, polyurethane (PU), polydimethylsiloxane (PDMS), dielectric elastomer (VHB), and hydrogel. High aspect ratio (~1.4) and well-defined (taper ratio <0.1) straight micropillars with different cross-sections, as well as complex surface patterns assembled by bent micropillars, can be rapidly prepared via femtosecond laser scribing at a growth speed up to 130 μm/s. Benefiting from the athermal nature of the process, the minimum feature size reaches 15 μm and may be further reduced by employing more precise techniques such as focused ion beam (FIB) etching. Such improvements in patterning resolution would enable finer control over local stress release and potentially allow submicron-resolution stress gradient modulation, thereby opening opportunities for the fabrication of more complex microstructures. The structural tunability is achieved by simply releasing and re-stretching the membrane, allowing surface morphologies to reversibly switch between flat and structured states within 30 seconds. This reconfigurability is experimentally validated and well-supported by simulations. The high aspect ratio is essential for functional applications, as it enhances tactile perception and enables programmable bending for multidirectional information encoding. These characteristics underpin practical demonstrations in Braille training and reversible information encryption/decryption. Compared to our previously reported laser-induced polymer self-growth (LIPS) method, which is limited to heat-shrinkable shape memory polymers and generates irreversible structures, the SIPS method significantly broadens the range of usable materials and enables reversible structural tuning.

Although the present work focuses on pristine elastomeric membranes, prior studies suggest that the incorporation of well-dispersed nanofillers could further enhance fatigue resistance and long-term durability40,41. Beyond mechanical reinforcement, multifunctional nanofillers—such as magnetic or photothermal nanoparticles—may impart additional stimulus-responsive or actuation functionalities to SIPS-generated microstructures. Such material-level functionalization, combined with the programmable self-growth enabled by SIPS, offers a promising route toward multifunctional soft microdevices and application-oriented extensions in future work.

Overall, our presented method combining femtosecond laser cutting and stretching of elastic membranes provides a robust and flexible platform for the rapid fabrication of reconfigurable microstructures, offering new opportunities in the fields of micro/nanofabrication, adaptive surfaces, and tactile interfaces.

Methods
Preparation of materials
Silicone membranes (thickness: 2 mm) were purchased from Pureshi in Taobao and cut into symmetrical cruciform shapes. Each silicone membrane was mounted on a custom-built biaxial stretching stage and stretched 30 mm in both directions using either manual or motorized rotating shafts. Silicon microspheres (diameter: 150–200 μm) were purchased from Knowledge & Benefit Sphere Tech. Co., Ltd. A commercial acrylic dielectric elastomer film (VHB™ 4910, 3M Company, USA) was employed as the dielectric elastomer substrate. Photo-crosslinkable poly(vinyl alcohol) (PVA)–based hydrogels were prepared by first dissolving PVA (0.2 wt%, molecular weight 75,000–79,000 g·mol⁻¹) in deionized water under magnetic stirring until complete dissolution. Subsequently, acrylamide (40 wt%), poly(ethylene glycol) diacrylate (PEGDA, 2 wt%), and a photoinitiator (Irgacure 2959, 1 wt%) were added to the solution and thoroughly mixed. The resulting precursor solution was injected into a mold and cured under ultraviolet illumination (365 nm) for 5 min to obtain a hydrogel film. Carbon nanotube (CNT)–doped elastomer samples were prepared using Dragon Skin™ 10 Slow silicone (Smooth-On). Briefly, CNTs (360 mg) were first dispersed in cyclohexane (25 mL) by magnetic stirring followed by ultrasonication for ~30 min, with intermittent water replacement to maintain the temperature below 30°C, until a homogeneous black dispersion was obtained. The CNT dispersion was then added to Part A of Dragon Skin 10 Slow (29.82 g) and mixed thoroughly in a fume hood, allowing cyclohexane to evaporate completely. After solvent removal, an equal mass of Part B (29.82 g) was added and mixed uniformly. The mixture was subsequently degassed under vacuum to remove trapped air bubbles, cast into molds, and cured at 65°C for 20 min to obtain CNT-doped elastomer films.

Stretch-induced polymer self-growth
A femtosecond laser system (Legend Elite-1K-HE, Coherent, USA; pulse width: 104 fs; repetition rate: 1 kHz; wavelength: 800 nm) was used to induce polymer self-growth. The laser beam was guided onto the biaxially stretched silicone membrane surface by a galvo scanner system (SCANLAB, Germany). Scanning paths were designed in AutoCAD 2019 and exported as dxf files, which were then imported into Samlight (SCANLAB) for laser control. Laser scribing was conducted either continuously or intermittently to locally release material stress. The number of laser scans was controlled by Samlight software, while laser power and scanning speed were fixed at 50 mW and 50 mm/s, respectively. To reduce the minimum feature size, the laser was focused using a 20X objective lens (OLYMPUS, Japan), and the sample was translated by a motorized 2D stage (MLS203-1, Thorlabs, USA), resulting in micro-pillars with minimum diameters of 15 μm.

Characterization
Side- and top-view optical images and videos of micropillars were recorded by a CCD (Mindvision, Chnia) equipped with optical lenses. Due to the size constraints of the SEM chamber, the stretched membrane was fixed onto a rigid plastic plate with screws, then trimmed for SEM imaging (JSM-6700F, JEOL, Japan). Laser confocal microscopy was performed using OLS5000 (OLYMPUS, Japan). The fingertip contact force on Braille micropillars was measured by a precise force sensor under the stage (HZC-T, Chengying Sensor Co., Ltd. Bengbu, China).

Data availability
All the data that support the findings of this study are included in the Article and its Supplementary Information. Source data are available via Figshare at https://doi.org/10.6084/m9.figshare.31331896. All data are available from the corresponding author upon request.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This is a highly creative manuscript that introduces a fundamentally new and elegant approach to fabricate tunable\nmicrostructures via Stretch-Induced Polymer Self-growth (SIPS). By ingeniously coupling femtosecond laser scribing with\nmechanical pre-stretching, the authors not only demonstrate a method with remarkable reversibility, high aspect ratio (~1.4),\nand fast fabrication speed (~130 μm/s), but also enable functionalities rarely seen in prior self-growth techniques—such as\ndirectional bending, reversible tactile Braille, and in-situ information encryption/decryption. What makes this work particularly\nnovel and engaging is its biologically inspired mechanism, material generality, and the potential to reshape how we think\nabout microstructure formation—not as static architectures, but as reconfigurable, information-rich surfaces. This aligns with\nthe growing demand for adaptive soft systems in areas ranging from smart haptics to human–machine interfaces. The\nmanuscript is technically sound, conceptually original, and clearly written. I believe it will strongly appeal to a wide audience\nspanning micro/nano fabrication, soft robotics, surface engineering, and functional materials. I recommend minor revision to\naddress several clarifications before final acceptance.\n1. While the authors show excellent cyclic performance of the micropillar structures, it would be helpful to qualitatively\ndemonstrate the long-term durability after repeated cycles (eg. 100 cycles).\n2. While the authors show that PDMS and Ecoflex can be used, could the authors comment on limitations?\n3. Could SIPS be extended to dielectric elastomers (e.g., VHB) that are widely used in soft actuators?", "reviewer_2": "This manuscript presents an innovative \"stretch-induced polymer self-growth (SIPS)\" methodology, enabling rapid\nfabrication of reversible, high-aspect-ratio microstructures via femtosecond laser scribing on pre-stretched elastic\nmembranes. It demonstrates significant advantages over existing chemically driven approaches in material versatility,\nprocessing speed, and structural controllability. The work exhibits outstanding innovation and strong application potential,\nrendering it suitable for publication. However, the following critical questions regarding the manuscript content require\nattention:\n1.While the manuscript confirms SIPS applicability to elastomers (e.g., silicone, PU, PDMS), it does not address the\ninfluence of critical mechanical properties (such as yield strength and fracture elongation) on self-growth. Within what range\nof Young’s modulus or stretching ratio (λ) would micropillar formation be inhibited?\n2.The manuscript mentions structural stability over 10 stretching cycles (Fig. 4l-m), yet the fatigue failure threshold remains\nunquantified. Could stress concentration at laser-scribed grooves during repeated cycling induce microcracks? Can material\nmodifications (e.g., incorporating nanofillers) enhance durability?\n3.The bending angle controllability of micropillars relies on the additional scribing depth H₃ (Fig. 4i). Is it feasible to achieve\nsubmicron-resolution stress gradient design to fabricate more complex topologies (e.g., helices, fractals)?\n4.Can the SIPS strategy be extended to soft matter systems beyond elastomers, such as hydrogels or biological tissues?\n5.The tunable Braille training platform is novel in design. However, the material’s limitations in fatigue resistance still exist.\nWould it be possible to increase the number of reversible cycles and establish the fatigue threshold for practical Braille\ntraining applications?"}, "author_response": "Reply to the Reviewers’ comments\nThank you for coordinating the review process for our manuscript, and we sincerely\nappreciate all the reviewers for their positive evaluations and valuable comments. The\nreviewer’s comments have been carefully considered, and additional experiments have\nbeen carried out to address specific concerns. The manuscript has been carefully revised\nwith major changes marked in red. The point-by-point responses to the comments are\nlisted below.\nReviewer #1 (Remarks to the Author):\nThis is a highly creative manuscript that introduces a fundamentally new and\nelegant approach to fabricate tunable microstructures via Stretch-Induced\nPolymer Self-growth (SIPS). By ingeniously coupling femtosecond laser scribing\nwith mechanical pre-stretching, the authors not only demonstrate a method with\nremarkable reversibility, high aspect ratio (~1.4), and fast fabrication speed\n(~130 μm/s), but also enable functionalities rarely seen in prior self-growth\ntechniques—such as directional bending, reversible tactile Braille, and in-situ\ninformation encryption/decryption. What makes this work particularly novel and\nengaging is its biologically inspired mechanism, material generality, and the\npotential to reshape how we think about microstructure formation—not as static\narchitectures, but as reconfigurable, information-rich surfaces. This aligns with\nthe growing demand for adaptive soft systems in areas ranging from smart haptics\nto human–machine interfaces. The manuscript is technically sound, conceptually\noriginal, and clearly written. I believe it will strongly appeal to a wide audience\nspanning micro/nano fabrication, soft robotics, surface engineering, and\nfunctional materials. I recommend minor revision to address several clarifications\nbefore final acceptance.\n1. While the authors show excellent cyclic performance of the micropillar\nstructures, it would be helpful to qualitatively demonstrate the long-term\ndurability after repeated cycles (eg. 100 cycles).\nResponse: We thank the reviewer for this insightful comment. To qualitatively and\nquantitatively evaluate the long-term durability of the self-grown microstructures, we\nperformed systematic stretching–release tests over 1000 cycles. It should be noted that\nthese experiments were conducted using a custom-built biaxial stretching platform, in\nwhich each stretching–release cycle involves relatively slow and carefully controlled\nloading and unloading to ensure accurate strain application and structural\ncharacterization. Owing to the absence of a high-frequency commercial fatigue testing\nmachine, the total number of cycles was limited to 1000 in the present study.\nFig. R1 Long-term cyclic durability of straight micropillars under repeated stretching–release\ncycles. Three-dimensional laser confocal microscopy images of three straight micropillars with\nincreasing laser scribing depths (H₂) in (a) the pristine state, (b) after 200 stretching–release cycles,\nand (c) after 1000 cycles. (d) Quantitative evolution of the laser scribing depth (H₂), (e) micropillar\nheight (H₁), and (f) micropillar diameter (D) as a function of the number of stretching–release cycles.\nFor the straight micropillars (Fig. R1), three representative structures with\nprogressively increasing heights were fabricated by gradually increasing the laser\nscribing depth (H₂). Their geometric parameters, including scribing depth, micropillar\nheight, and diameter, were characterized after 0, 200, 400, 600, 800, and 1000\nstretching–release cycles. The results show that the micropillar height increases during\nthe initial 200 cycles due to the progressive deepening of the laser-scribed grooves,\nwhile the micropillar diameter remains independent of the cycling number, and all\ngeometric parameters then reach a stable plateau with no measurable structural\ndegradation observed up to 1000 cycles.\nFig. R2 Long-term cyclic durability of bent micropillars under repeated stretching–release\ncycles. Three-dimensional laser confocal microscopy images of three bent micropillars with\nincreasing additional laser scribing depths (H ) in (a) the pristine state, (b) after 200 stretching–\n3\nrelease cycles, and (c) after 1000 cycles. (d) Quantitative evolution of the laser scribing depth\n(H₂+H ), (e) micropillar bending angle (α), and (f) micropillar length (L) as a function of the number\n3\nof stretching–release cycles.\nFor the bent micropillars (Fig. R2), three structures with progressively increasing\nbending angles were fabricated using increasing additional scribing depths (H ). The\n3\nlaser scribing depth (H₂+H ), bending angle, and pillar length were measured at the\n3\nsame cycle numbers. Similar to the straight micropillars, the bending angle and pillar\nlength show a slight increase during the first 200 cycles in correlation with the gradual\ndeepening of the laser-scribed grooves, and subsequently remain stable from 200 to\n1000 cycles.\nThese results indicate that the laser-scribed grooves undergo minor geometric\nadaptation during the early cycling stage, after which both straight and bent micropillars\nreach a mechanically stable configuration. Importantly, no fracture, collapse, or loss of\nreversibility is observed after 1000 stretching–release cycles, demonstrating the\nexcellent long-term durability and cyclic stability of the SIPS-fabricated\nmicrostructures.\nRevision: In accordance with the reviewer’s comments, Figures R1 and R2 have been\nincorporated into the revised manuscript and the supplementary information.\nPage 9, Line 17 – Line 18: “as further confirmed by the additional cyclic durability\nresults shown in Figure S19.” has been added.\nPage 11, Line 11 – Line 12: “These trends are further confirmed by extended cyclic\nstretching–release tests up to 1000 cycles, as shown in Figure S24.” has been added.\nAdditional Figures (Supplementary Fig. 19 and Fig. 24) and corresponding captions\nhave been added to the revised supplementary information.\n2. While the authors show that PDMS and Ecoflex can be used, could the authors\ncomment on limitations?\nResponse: We thank the reviewer for this helpful comment. We first clarify that Dragon\nSkin 10 (slow) was previously mistakenly referred to as Ecoflex, and this has now been\ncorrected throughout the revised manuscript. Although both PDMS and Dragon Skin\n10 are compatible with the SIPS strategy, their intrinsic mechanical properties lead to\ndistinct practical limitations.\nPDMS and Dragon Skin 10 elastomers exhibit markedly different fracture\nelongations, which directly determine their maximum achievable stretching ratios\nduring SIPS processing. Specifically, PDMS (Sylgard 184, 10:1) typically shows an\nelongation at break of approximately 100%[1], corresponding to a critical stretch ratio\nλ of ~2. In contrast, Dragon Skin 10 exhibits a much higher fracture strain of\napproximately 500% under standardized tensile testing conditions[1], which\ncorresponds to a stretch ratio λ of ~6. Consequently, Dragon Skin 10 provides a\nsubstantially broader stretching window and enables larger deformation amplitudes,\nwhereas PDMS is restricted to a narrower but still sufficient elastic deformation range.\n3. Could SIPS be extended to dielectric elastomers (e.g., VHB) that are widely used\nin soft actuators?\nResponse:\nFig. R3 SIPS-enabled self-growth of micropillars on a biaxially stretched VHB elastomer. (a)\nOptical photograph of a VHB elastomer film mounted on a biaxial stretching platform. (b) Three-\ndimensional confocal microscopy image of three micropillars fabricated on the VHB film using the\nSIPS process. (c) Corresponding height profiles of the micropillars shown in (b), revealing tunable\npillar heights ranging from approximately 55 to 91 μm.\nWe thank the reviewer for this insightful question. To examine whether the SIPS\nstrategy can be extended to dielectric elastomers commonly used in soft actuators, we\nconducted proof-of-concept experiments using a commercial dielectric elastomer film\n(VHB 4910, Fig. R3). The VHB film was mounted on a biaxial stretching platform and\npre-stretched to a stretch ratio of 1.44. Femtosecond laser scribing was then performed\nalong circular paths with a diameter of 0.15 mm. Upon localized release of the applied\nstrain induced by laser scribing, self-grown micropillars were successfully formed.\nThese results demonstrate that SIPS is also applicable to dielectric elastomers, with the\nmicropillar height similarly governed by the laser scribing depth, yielding pillar heights\nin the range of approximately 55–91 μm. It should be noted that, owing to the high\noptical transparency of dielectric elastomers such as VHB, three-dimensional confocal\nimaging exhibits reduced surface contrast, which limits the quantitative visualization\nof the resulting microstructures.\nImportantly, dielectric elastomers provide additional opportunities beyond passive\nmechanical deformation. In future work, the intrinsic electromechanical coupling of\ndielectric elastomers may enable rapid and reversible modulation of the self-grown\nmicrostructures by dynamically tuning the applied voltage, offering a pathway toward\nelectrically programmable microstructure switching.\nRevision: In accordance with the reviewer’s comments, Figure R3 has been\nincorporated into the revised manuscript and the supplementary information.\nPage 5, Line 24 – Line 26: “Dragon Skin 10 silicone elastomer mixed with carbon\nnanotubes, dielectric elastomer (VHB) and hydrogel (Figure S7-8).” has been revised.\nPage 2, Line 6: “dielectric elastomer (VHB), and hydrogel” has been added.\nPage 15, Line 22: “dielectric elastomer (VHB), and hydrogel” has been added.\nSupplementary Fig. 8 and corresponding caption have been added to the revised\nsupplementary information.\nReviewer #2 (Remarks to the Author):\nThis manuscript presents an innovative \"stretch-induced polymer self-growth\n(SIPS)\" methodology, enabling rapid fabrication of reversible, high-aspect-ratio\nmicrostructures via femtosecond laser scribing on pre-stretched elastic\nmembranes. It demonstrates significant advantages over existing chemically\ndriven approaches in material versatility, processing speed, and structural\ncontrollability. The work exhibits outstanding innovation and strong application\npotential, rendering it suitable for publication. However, the following critical\nquestions regarding the manuscript content require attention:\n1.While the manuscript confirms SIPS applicability to elastomers (e.g., silicone,\nPU, PDMS), it does not address the influence of critical mechanical properties\n(such as yield strength and fracture elongation) on self-growth. Within what range\nof Young’s modulus or stretching ratio (λ) would micropillar formation be\ninhibited?\nResponse: We thank the reviewer for this important question regarding the influence\nof critical mechanical properties on SIPS-induced self-growth. As demonstrated in the\nmain text, the geometry of the self-grown micropillars is governed by the applied\nstretching ratio (λ) and the laser scribing depth (H\n2\n). From a mechanical perspective, critical material properties such as fracture elongation and yield-like deformation\nbehavior inherently constrain the accessible stretching ratio, and therefore influence the\nresulting micropillar geometry.\nThe upper limit of the stretching ratio is constrained by two factors. First, the\nfracture elongation (F) defines a geometric limit, because λ must remain below the\nfracture strain to avoid macroscopic failure (Fig. R4). Specifically, the measured\nelongations at break are approximately 275% for silicone, 500% for PU, and 125% for\nPDMS, corresponding to maximum stretch ratios of λ ≈ 3.75, 6.0, and 2.25, respectively.\nSecond, for elastomeric materials, the effective stretching ratio accessible for SIPS is\ngoverned by the deformation regime. Unlike metals, elastomers do not exhibit a distinct\nyield point. Instead, yielding corresponds to a gradual transition from elastic-dominated\ndeformation to viscoelastic dissipation and irreversible molecular rearrangement at\nlarge strains[2]. This deformation-regime transition is quantitatively reflected in the\nstrain-dependent slope (tangent modulus) of the stress–strain curves, which is\ncommonly used to characterize deformation mechanisms in elastomers[3].\nFig. R4 Stress–strain behavior of representative elastomeric materials used in this study.\nEngineering stress–strain curves of (a) silicone elastomer, (b) polyurethane (PU), and (c)\npolydimethylsiloxane (PDMS), measured from three independent specimens under identical\nuniaxial tensile conditions. All three materials exhibit continuous, nonlinear deformation behavior\nwith good reproducibility. The measured elongations at break are approximately 275% for silicone,\n500% for PU, and 125% for PDMS, corresponding to maximum stretch ratios of λ ≈ 3.75, 6.0, and\n2.25, respectively.\nOur experimental measurements show that silicone exhibits a smooth stress–strain\nresponse with only modest variation in tangent modulus over a wide strain range,\nindicating predominantly elastic-dominated deformation with no pronounced yield-like\ntransition (Fig. R4). In contrast, PU displays an initially high tangent modulus followed\nby a pronounced reduction at intermediate-to-large strains, consistent with a transition\ntoward dissipation-dominated deformation associated with microstructural\nrearrangement, as reported for polyurethanes[4]. PDMS shows a different behavior\nwith the tangent modulus increasing markedly at large strains due to strain hardening\nassociated with finite chain extensibility, consistent with established constitutive\nmodels for rubber elasticity[5]. These distinct deformation responses indicate that,\nwhile no sharp yield point is observed for silicone, PU, or PDMS, yield-like transitions\ncan occur in the form of increased dissipation or strain hardening. When such yield-like\ndeformation becomes significant, part of the applied stretching may become\nirreversible, which can compromise the reversibility of the self-grown microstructures\nand hinder complete retraction of the micropillars into the substrate upon release.\nOwing to its predominantly elastic-dominated response, silicone is a favorable substrate\nfor SIPS-induced self-growth.\nYoung’s modulus itself does not play a decisive role in determining micropillar\ngeometry. This conclusion is supported by finite-element simulations presented in the\nsupplementary information Figure S14, as well as additional experiments using\nmaterials with significantly different Young’s moduli (PU, E ≈ 9.25 MPa; Silicone, E ≈\n3.37 MPa). When processed under comparable stretching ratios and laser scribing\ndepths, both materials produce micropillars with similar heights and diameters,\nsuggesting that elastic stiffness does not play a dominant role in determining the self-\ngrowth outcome (Fig. R5).\nFig. R5 Comparison of SIPS-induced micropillar profiles on PU and Silicone with different\nYoung’s moduli.\nWhen the stretching ratio is very small, only shallow surface protrusions are\nformed rather than fully developed micropillars. This trend is further quantified by\nnumerical simulations, which establish a monotonic relationship between stretching\nratio and protrusion height in the low-λ regime (Fig. R6). Experimentally, resolving\nsuch shallow protrusions at extremely low stretching ratios requires ultrahigh precision\nin both stretching control and three-dimensional height characterization. Moreover,\nintrinsic thickness nonuniformity of the elastomeric membranes can introduce\nadditional uncertainty, making it difficult to unambiguously distinguish protrusion\nheights induced by stretching from pre-existing thickness variations. Owing to these\ncombined limitations, a definitive experimental threshold stretching ratio for complete\ninhibition of micropillar formation was not determined.\nFig. R6 Simulated relationship between stretching ratio and protrusion height in the low-λ\nregime.\nRevision: In accordance with the reviewer’s comments, Figures R4 and R5 have been\nincorporated into the revised manuscript and the supplementary information.\nPage 8, Line 6- Line 27: “The accessible stretching ratio λ in SIPS is constrained\nby the mechanical properties of the elastomeric substrate. First, the fracture elongation\n(F) defines an upper limit, since λ must remain below the fracture strain to avoid\nmacroscopic failure (Figure S16). The measured elongations at break are\napproximately 275% for silicone, 500% for PU, and 125% for PDMS, corresponding\nto maximum stretch ratios of λ ≈ 3.75, 6.0, and 2.25, respectively. Second, the effective\nstretching ratio accessible for SIPS is governed by the deformation regime of the\nmaterial. Unlike metals, elastomers do not exhibit a distinct yield point and instead\nundergo a continuous transition from elastic-dominated deformation to viscoelastic\ndissipation at large strains[2], which is reflected in the strain-dependent slope (tangent\nmodulus) of the stress–strain curves[3].\nSilicone exhibits a smooth stress–strain response with only modest variation in tangent\nmodulus over a wide strain range, indicating predominantly elastic-dominated\ndeformation (Figure S16). In contrast, PU shows a reduction in tangent modulus at\nintermediate-to-large strains due to dissipation-dominated deformation, as reported for\npolyurethanes[4]. PDMS exhibits a pronounced increase in tangent modulus at large\nstrains due to strain hardening associated with finite chain extensibility, consistent with\nestablished constitutive models of rubber elasticity[5]. When yield-like deformation in\nPU and PDMS becomes significant, part of the applied stretching may become\nirreversible, which can compromise the reversibility of the self-grown microstructures\nand hinder complete retraction of the micropillars into the substrate upon release.\nOwing to its predominantly elastic-dominated response, silicone is therefore a\nfavorable substrate for SIPS-induced self-growth.” has been added.\nSupplementary Fig. 15 and Fig. 16 and corresponding captions have been added to the\nrevised supplementary information.\n2. The manuscript mentions structural stability over 10 stretching cycles (Fig. 4l-\nm), yet the fatigue failure threshold remains unquantified. Could stress\nconcentration at laser-scribed grooves during repeated cycling induce\nmicrocracks? Can material modifications (e.g., incorporating nanofillers) enhance\ndurability?\nResponse: We thank the reviewer for this insightful comment. To qualitatively and\nquantitatively evaluate the long-term durability of the self-grown microstructures, we\nperformed systematic cyclic stretching–release tests over 1000 cycles on both straight\nand bent micropillars. It should be noted that these experiments were conducted using\na custom-built biaxial stretching platform, in which each stretching–release cycle\ninvolves relatively slow and carefully controlled loading and unloading to ensure\naccurate strain application and structural characterization. Owing to the absence of a\nhigh-frequency commercial fatigue testing machine, the total number of cycles was\nlimited to 1000 in the present study.\nFor the straight micropillars (Fig. R1), three representative structures with\nprogressively increasing heights were fabricated by gradually increasing the laser\nscribing depth (H₂). Their geometric parameters, including scribing depth, micropillar\nheight, and diameter, were characterized after 0, 200, 400, 600, 800, and 1000\nstretching–release cycles. The results show that the micropillar height increases during\nthe initial 200 stretching–release cycles, while the micropillar diameter remains\nindependent of the cycling number. This early-stage evolution is attributed to the\nformation and limited extension of microcracks along the laser-scribed grooves under\ncyclic loading, which leads to a progressive deepening of the grooves. Importantly, this\ncrack-related evolution is confined to the early cycling stage and does not evolve into\nuncontrolled crack propagation or structural failure. Beyond approximately 200 cycles,\nthe groove geometry stabilizes, and all geometric parameters reach a clear plateau, with\nno further crack growth or measurable structural degradation observed up to 1000\ncycles.\nFig. R1 Long-term cyclic durability of straight micropillars under repeated stretching–release\ncycles. Three-dimensional laser confocal microscopy images of three straight micropillars with\nincreasing laser scribing depths (H₂) in (a) the pristine state, (b) after 200 stretching–release cycles,\nand (c) after 1000 cycles. (d) Quantitative evolution of the laser scribing depth (H₂), (e) micropillar\nheight (H₁), and (f) micropillar diameter (D) as a function of the number of stretching–release cycles.\nFor the bent micropillars (Fig. R2), three structures with progressively increasing\nbending angles were fabricated using increasing additional scribing depths (H ). The\n3\nlaser scribing depth (H₂+H ), bending angle, and pillar length were measured at the\n3\nsame cycle numbers. Both the bending angle and pillar length show a slight increase\nduring the first 200 stretching–release cycles, which is attributed to limited crack-\ninduced groove deepening under cyclic loading. Thereafter, all measured parameters\nremain stable from 200 to 1000 cycles, indicating robust structural stability of the bent\nmicropillars.\nThese results indicate that the laser-scribed grooves undergo minor geometric\nadaptation during the early cycling stage, after which both straight and bent micropillars\nreach a mechanically stable configuration. Importantly, no fracture, collapse, or loss of\nreversibility is observed after 1000 stretching–release cycles, demonstrating the\nexcellent long-term durability and cyclic stability of the SIPS-fabricated\nmicrostructures.\nFig. R2 Long-term cyclic durability of bent micropillars under repeated stretching–release\ncycles. Three-dimensional laser confocal microscopy images of three bent micropillars with\nincreasing additional laser scribing depths (H ) in (a) the pristine state, (b) after 200 stretching–\n3\nrelease cycles, and (c) after 1000 cycles. (d) Quantitative evolution of the laser scribing depth\n(H₂+H ), (e) micropillar bending angle (α), and (f) micropillar length (L) as a function of the number\n3\nof stretching–release cycles.\nIn the present work, the SIPS experiments were primarily conducted on a\ncommercial silicone membrane, which is supplied as a prefabricated film and therefore\ndoes not allow the incorporation of nanofillers. To preliminarily explore the feasibility\nof nanofiller reinforcement, we performed additional tests using Dragon Skin 10\nelastomer with incorporated carbon nanotubes (CNTs). CNTs were first dispersed in\ncyclohexane via ultrasonic treatment and then mixed into the Part A component of\nDragon Skin 10, followed by solvent evaporation, addition of Part B, degassing,\nmolding, and thermal curing. However, when the CNT-doped Dragon Skin 10 films\nwere mounted on the stretching platform, the membranes fractured within several\nminutes under tensile loading. This premature failure indicates that non-uniform\ndispersion of nanofillers can significantly reduce the fracture elongation of the\nelastomer, thereby narrowing the available stretching window required for stable SIPS\nprocessing. Because achieving homogeneous nanofiller dispersion and optimizing the\ncomposite formulation would require extensive additional process development beyond\nthe scope of the present study, we did not further pursue this direction here.\nImportantly, prior studies have demonstrated that, when properly dispersed,\nnanofillers can indeed enhance the mechanical durability, fatigue resistance, and\nfracture toughness of elastomeric materials[6, 7]. These works suggest that nanofiller\nreinforcement remains a promising strategy for improving long-term durability when\ndispersion and interfacial bonding are well controlled. Looking forward, we plan to\nsystematically investigate nanocomposite elastomer membranes with improved\ndispersion strategies, including the incorporation of magnetic or photothermal\nnanomaterials. Beyond potentially enhancing mechanical durability, such functional\nfillers could endow SIPS-fabricated microstructures with additional capabilities, such\nas magnetic actuation or photothermal responsiveness. Improved durability through\nnanofiller reinforcement would further facilitate the translation of the SIPS strategy\ntoward practical applications.\nRevision: In accordance with the reviewer’s comments, Figures R1 and R2 have been\nincorporated into the revised manuscript and the supplementary information.\nPage 9, Line 17 – Line 18: “as further confirmed by the additional cyclic durability\nresults shown in Figure S19.” has been added.\nPage 11, Line 11 – Line 12: “These trends are further confirmed by extended cyclic\nstretching–release tests up to 1000 cycles, as shown in Figure S24.” has been added.\nPage 16, Line 14 – Line 21: “Although the present work focuses on pristine elastomeric\nmembranes, prior studies suggest that the incorporation of well-dispersed nanofillers\ncould further enhance fatigue resistance and long-term durability. Beyond mechanical\nreinforcement, multifunctional nanofillers—such as magnetic or photothermal\nnanoparticles—may impart additional stimulus-responsive or actuation functionalities\nto SIPS-generated microstructures. Such material-level functionalization, combined\nwith the programmable self-growth enabled by SIPS, offers a promising route toward\nmultifunctional soft microdevices and application-oriented extensions in future work.”\nhas been added in the discussion part.\nAdditional Figures (Supplementary Fig. 19 and Fig. 24) and corresponding captions\nhave been added to the revised supplementary information.\n3.The bending angle controllability of micropillars relies on the additional scribing\ndepth H₃ (Fig. 4i). Is it feasible to achieve submicron-resolution stress gradient\ndesign to fabricate more complex topologies (e.g., helices, fractals)?\nResponse: We thank the reviewer for this insightful and forward-looking suggestion.\nIndeed, achieving submicron-resolution stress gradient design would be highly\nattractive for fabricating more complex topologies, such as helices or fractal\narchitectures, using the SIPS strategy.\nAt present, the realization of continuously varying laser scribing depth along a\nspiral trajectory remains technically challenging with our current processing system,\nbecause the laser energy and scanning speed cannot be modulated in real time during\ngalvo-based scanning. Although the laser spot size and nominal depth control precision\nare on the order of several micrometers, the presence of large pre-stored elastic stress\nin the stretched elastomer causes the laser-scribed grooves to widen to tens of\nmicrometers. As a result, it is difficult to implement submicron-scale, continuously\ngraded stress fields required for deterministic programming of helical or fractal\ntopologies.\nFig. R7 Numerical simulation of self-grown micropillar under spiral laser scribing trajectories\nTo nonetheless assess the feasibility of such complex stress-gradient designs, we\nperformed numerical simulations by prescribing a spiral modulation of the additional\nscribing depth H₃ (Fig. R7). In the simulations, a circular scanning path with a diameter\nof 360 μm was considered, with a base scribing depth H₂ of 105 μm. The additional\ndepth H₃ was increased helically with a pitch of 112 μm, corresponding to one full turn\nof the spiral. Spiral turn numbers of 0.1, 0.3, 0.5, 0.7, and 1.0 were simulated. The\nsimulated results show that a spiral variation in scribing depth can indeed induce a\nhelical modulation of the bending direction of the resulting microstructure. However,\nthe overall morphology remains a micropillar-like structure rather than a fully\ndeveloped helical topology. Achieving true helical architectures will therefore require\nfurther methodological developments, such as enhanced spatial resolution, more\nprecise stress-gradient control, or alternative self-growth strategies beyond the present\nimplementation.\nAs a complementary route toward higher-order architectures, we demonstrate that\nfractal structures can be realized by designing the laser processing path and using four\noutward-bending micropillars arranged radially as fundamental building blocks (Fig.\nR8). Although these structures may not be the strict mathematical fractals that the\nreviewer had in mind, they demonstrate the flexibility of the proposed self-growth\nstrategy.\nFig. R8 Fractal structure fabrication based on bent micropillar building blocks. (a) Schematic\nillustration of the laser scanning trajectories for a fundamental building unit. The blue circular paths\nindicate the primary laser scribing depth (H₂), while the black semicircular arcs represent the\nadditional scribing depth (H₃) used to program the bending direction of the micropillars. (b) Optical\nmicrograph of the fabricated fractal structure composed of bent micropillars assembled according\nto the designed scanning trajectories. Scale bar, 2 mm.\nRevision: In accordance with the reviewer’s comments, we have added a discussion in\nthe Discussion section on the potential for fabricating more complex microstructures.\nPage 15, Line 28- Page 16, Line 3: “Such improvements in patterning resolution would\nenable finer control over local stress release and potentially allow submicron-\nresolution stress gradient modulation, thereby opening opportunities for the fabrication\nof more complex microstructures.”\n4.Can the SIPS strategy be extended to soft matter systems beyond elastomers,\nsuch as hydrogels or biological tissues?\nResponse: We thank the reviewer for this important question regarding the applicability\nof the SIPS strategy to soft matter systems beyond elastomers. To explore this\npossibility, we conducted proof-of-concept experiments on both synthetic hydrogels\nand biological tissues.\nFor hydrogels, we prepared a photo-crosslinkable poly(vinyl alcohol)–based\nhydrogel precursor by dissolving PVA (0.2 wt%, molecular weight 75,000–79,000\ng/mol) in deionized water under magnetic stirring. Subsequently, acrylamide (40 wt%),\npoly(ethylene glycol) diacrylate (PEGDA, 2 wt%), and a photoinitiator (Irgacure 2959,\n1 wt%) were added and fully dissolved. The precursor solution was injected into a mold\nand cured under 365 nm UV illumination for 5 min to obtain a hydrogel film. After\nbiaxial stretching and fixation at a stretching ratio of 1.2, femtosecond laser scribing\nalong circular paths with a diameter of 0.5 mm was performed. By adjusting the laser\nscribing depth, three hydrogel-based micropillars with height of ~125 μm were\nsuccessfully fabricated, demonstrating that SIPS can be extended to soft, water-rich\npolymer networks (Fig. R9). It should be noted that three-dimensional confocal\nimaging did not clearly reveal the laser-scribed grooves in the hydrogel. This is\nprimarily attributed to the rapid redistribution of water within the hydrogel matrix,\nwhich fills the laser-induced grooves. In addition, the high optical transparency of the\nhydrogel leads to strong subsurface light scattering, resulting in a rough and low-\ncontrast appearance in confocal images.\nFig. R9 SIPS fabrication of micropillars on a biaxially stretched hydrogel. (a) Optical\nphotograph of a hydrogel film mounted on a biaxial stretching platform. (b) Three-dimensional\nconfocal microscopy image of three micropillars fabricated on the hydrogel substrate using the\nSIPS process. (c) Corresponding height profile extracted from the confocal image, showing the\ncharacteristic protrusion height of the hydrogel micropillars.\nTo further assess applicability to biological soft matter, we selected chicken skin\nas a representative biological tissue (Fig. R10). Compared with synthetic elastomers\nand hydrogel, biological tissues present additional challenges, including intrinsic\nsurface roughness, structural heterogeneity, and a tendency toward delamination,\nshrinkage, and lipid exudation during processing. These factors complicate both\nmechanical control and optical characterization. Nevertheless, when chicken skin was\nstretched to a ratio of 1.3 and subjected to laser scribing under the stretched state,\nsurface protrusions with heights of approximately 70 μm were observed. This result\nconfirms that laser-scribing-induced microstructure self-growth can also be achieved in\nprestretched biological tissues. Owing to the strong scattering and nonuniform surface\nmorphology of the tissue, three-dimensional confocal imaging exhibited reduced\ncontrast and limited quantitative resolution, which restricted detailed morphological\nanalysis. For this reason, the chicken skin results are provided as a qualitative\ndemonstration of feasibility. We appreciate the reviewer’s insightful suggestion, as\nachieving high-quality, controllable self-growth in biological tissues represents a\npromising direction that warrants further systematic investigation in future studies.\nFig. R10 Proof-of-concept demonstration of SIPS-induced microstructures on biological tissue\n(Chicken skin). (a) Optical photograph of chicken skin mounted on a biaxial stretching platform.\n(b) Top-view optical micrograph of three micropillar-like protrusions fabricated on chicken skin.\nThe white dashed circles indicate the locations of the microstructures, and surface lipid secretion\nfrom the tissue is visible. (c) Three-dimensional confocal microscopy image of the three\nmicrostructures formed on chicken skin. (d) Confocal height profile extracted from the rightmost\nmicrostructure, showing a protrusion height of approximately 70 μm. Owing to the intrinsic surface\nroughness, heterogeneity, and lipid exudation of chicken skin, the confocal imaging contrast is\nreduced, which limits the quantitative resolution of the reconstructed microstructures.\nFig. R3 SIPS-enabled self-growth of micropillars on a biaxially stretched VHB elastomer. (a)\nOptical photograph of a VHB elastomer film mounted on a biaxial stretching platform. (b) Three-\ndimensional confocal microscopy image of three micropillars fabricated on the VHB film using the\nSIPS process. (c) Corresponding height profiles of the micropillars shown in (b), revealing tunable\npillar heights ranging from approximately 55 to 91 μm.\nFurthermore, to examine whether the SIPS strategy can be extended to dielectric\nelastomers commonly used in soft actuators, we conducted proof-of-concept\nexperiments using a commercial dielectric elastomer film (VHB 4910, Fig. R3). The\nVHB film was mounted on a biaxial stretching platform and pre-stretched to a stretch\nratio of 1.44. Femtosecond laser scribing was then performed along circular paths with\na diameter of 0.15 mm. Upon localized release of the applied strain induced by laser\nscribing, self-grown micropillars were successfully formed. These results demonstrate\nthat SIPS is also applicable to dielectric elastomers, with the micropillar height\nsimilarly governed by the laser scribing depth, yielding pillar heights in the range of\napproximately 55–91 μm. It should be noted that, similar to the case of hydrogels, the\nhigh optical transparency of dielectric elastomers such as VHB leads to reduced surface\ncontrast in three-dimensional confocal imaging, which limits the quantitative\nvisualization of the resulting microstructures.\nImportantly, dielectric elastomers provide additional opportunities beyond passive\nmechanical deformation. In future work, the intrinsic electromechanical coupling of\ndielectric elastomers may enable rapid and reversible modulation of the self-grown\nmicrostructures by dynamically tuning the applied voltage, offering a pathway toward\nelectrically programmable microstructure switching.\nRevision: In accordance with the reviewer’s comments, Figure R3 and R9 have been\nincorporated into the revised manuscript and the supplementary information.\nPage 5, Line 24 – Line 26: “Dragon Skin 10 silicone elastomer mixed with carbon\nnanotubes, dielectric elastomer (VHB) and hydrogel (Figure S7-8).” has been revised.\nPage 2, Line 6: “dielectric elastomer (VHB), and hydrogel” has been added.\nPage 15, Line 22: “dielectric elastomer (VHB), and hydrogel” has been added.\nSupplementary Fig. 8 and corresponding caption has been added to the revised\nsupplementary information.\n5.The tunable Braille training platform is novel in design. However, the material’s\nlimitations in fatigue resistance still exist. Would it be possible to increase the\nnumber of reversible cycles and establish the fatigue threshold for practical Braille\ntraining applications?\nResponse: We thank the reviewer for this important question regarding the fatigue\nresistance and long-term usability of the tunable Braille training platform. To\nsystematically assess durability under practical operating conditions, we investigated\nthe fatigue behavior of the Braille micropillar structures under two representative\nloading modes: repeated stretching–release cycles and repeated tactile contact\n(touching/friction) cycles.\n1. Stretching–release fatigue tests.\nFig. R11 Geometric evolution of Braille micropillars as a function of stretching–release cycles\n(0–1000 cycles). (a) Laser scribing depth, (b) Micropillar height, (c) Micropillar diameter, (d)\nInterpillar spacing as a function of cycle number.\nThe Braille-patterned membrane was mounted on a stretching platform and\nsubjected to repeated stretching–release cycles of 0, 200, 400, 600, 800, and 1000\ncycles (Fig. R11). After each stage, the scribing depth, micropillar height, diameter,\nand interpillar spacing were quantified. During the first 200 cycles, the micropillar height\nincreased due to slight deepening of the laser-scribed grooves, while the diameter and\ninterpillar spacing remained essentially unchanged. All geometric parameters stabilized\nbeyond 200 cycles and showed no further evolution up to 1000 cycles.\n2. Repeated touching/friction tests.\nFig. R12 Geometric evolution of Braille micropillars under repeated tactile abrasion. (a)\nOptical photograph of the custom-built reciprocating abrasion platform used for tactile fatigue\ntesting. (b) Enlarged view of the abrasion head fabricated from Dragon Skin 10 elastomer (radius\nr=8 mm) in contact with the Braille micropillars. (c) Evolution of the laser scribing depth as a\nfunction of abrasion cycles (0–1000 cycles). (d) Time-sequenced optical images illustrating the\nfriction probe approaching the micropillar, deforming it through combined stretching and\ncompression, and then retracting. (e) Micropillar height, (f) Micropillar diameter, (g) Interpillar\nspacing as a function of abrasion cycles (0–2000 cycles), where 1–2 and 3–4 indicate the spacings\nbetween the corresponding micropillar pairs labelled in panel (b).\nTo better emulate practical Braille reading conditions, we further conducted cyclic\ntactile tests using a custom-built friction platform consisting of a motorized linear stage\nand a force sensor (Fig. R12). The friction probe was fabricated from Dragon Skin 10\nelastomer to match the elastic modulus of human skin, with a hemispherical curvature\nradius of 8 mm to approximate fingertip geometry. A normal load of 0.6 N was applied,\nconsistent with reported Braille reading forces in the literature[8]. The sample was\nsubjected to reciprocating friction along a fixed direction, with the sample rotated by\n90° after each friction cycle. This procedure was repeated for up to 2000 cycles.\nIt should be noted that the tactile tests were carried out on a custom-built friction platform\nrather than a high-frequency fatigue testing machine. Because each cycle involved\nmanual rotation of the sample and periodic removal of the specimen for confocal\ncharacterization, the total number of cycles was practically limited to 2000 in the\npresent study. Notably, this testing configuration closely reproduces realistic Braille\nusage conditions, in which the tactile probe directly contacts the substrate surface and\nthe applied frictional interaction induces substantial stretching and compressive\ndeformation of the elastomeric micropillars.\nDuring the touching tests, the scribing depth gradually decreased due to\nprogressive thinning of the substrate caused by friction (quantified up to 1000 cycles,\nbeyond which debris accumulation inside the grooves limited reliable measurement).\nSurprisingly, despite this substrate thinning, the micropillar height was observed to\ncontinuously increase from approximately 500 μm to 800 μm over the course of tactile\ncycling. This behavior can be attributed to the compliant deformation of the elastomeric\nmicropillars under repeated stretching and compression imposed by the friction probe\n(Fig.R12d), which promotes progressive out-of-plane elongation without material loss.\nBoth the micropillar diameter and the interpillar spacing remain essentially unchanged\nthroughout the entire process.\nTaken together, these results demonstrate that the Braille microstructures maintain\na stable spatial arrangement and structural integrity under both cyclic stretching and\nrepeated tactile loading, with no evidence of catastrophic fatigue failure within the\ntested ranges. During repeated stretching–release cycles, the micropillar height shows\na slight increase while the diameter remains essentially unchanged, leading to a\nmoderate increase in aspect ratio that is favorable for tactile perception and\ndiscrimination. Under repeated tactile loading, a more pronounced geometric evolution\nis observed. The micropillar height increases, while the diameter and interpillar spacing\nremains stable. As a result, the aspect ratio increases markedly from approximately 0.94\nto 1.43. This behavior arises from the compliant deformation of the elastomeric\nmicropillars, which accommodate repeated mechanical interactions through reversible\nbending and compression rather than material damage. Consequently, within the tested\ncycle range, the evolution toward higher-aspect-ratio Braille features helps preserve—\nand may modestly enhance—tactile saliency, indicating that repeated use does not lead\nto functional degradation of the Braille training platform. It should be noted, however,\nthat under much longer-term use involving tens or hundreds of thousands of tactile\ncycles, wear and material degradation of elastomeric substrates are expected to become\nunavoidable, which will be an important subject for future systematic fatigue and wear\nstudies.\nPrevious studies have shown that incorporating nanofillers into elastomeric\nmatrices can further enhance fatigue resistance and durability[6, 7]. While such material\nmodifications were not optimized in the present work, they represent a promising future\ndirection to extend the reversible cycling lifetime and establish well-defined fatigue\nthresholds for long-term Braille training applications.\nRevision: In accordance with the reviewer’s comments, Figures R11 and R12 have\nbeen incorporated into the revised manuscript and the supplementary information.\nPage 13, Line 26 – Page 15, Line 4: “To evaluate durability under practical\noperating conditions, we investigated the fatigue behavior of the Braille micropillar\nstructures under two representative loading modes: repeated stretching–release cycles\nand repeated tactile contact (touching/friction) cycles. In stretching–release tests, the\nBraille-patterned membrane was subjected to 0–1000 cycles, and the scribing depth,\nmicropillar height, diameter, and interpillar spacing were quantified (Figure S28).\nDuring the first 200 cycles, minor material tearing at the laser-scribed grooves led to\nan increase in groove depth, accompanied by a corresponding increase in micropillar\nheight, while the diameter and interpillar spacing remained essentially unchanged.\nBeyond 200 cycles, all geometric parameters reached a stable plateau and remained\nunchanged up to 1000 cycles.\nTo better emulate realistic Braille reading, cyclic tactile tests were performed\nusing a custom-built friction platform (Figure S29). A Dragon Skin 10 elastomer probe\nwith a hemispherical radius of 8 mm was used to approximate fingertip geometry and\ncompliance, and a normal load of 0.6 N was applied, consistent with reported Braille\nreading forces[8]. The sample was subjected to reciprocating friction along a fixed\ndirection, with the sample rotated by 90° after each friction cycle. This procedure was\nrepeated for up to 2000 cycles. During tactile cycling, the scribing depth gradually\ndecreased as a result of substrate thinning induced by friction, while the micropillar\nheight continuously increased from approximately 500 μm to 800 μm due to repeated\ncompression and stretching imposed by the abrasion head. The micropillar diameter\nand the interpillar spacing remained unchanged throughout the entire process.\nOverall, the Braille microstructures maintain a stable spatial arrangement and\nstructural integrity under both cyclic stretching and repeated tactile loading, with no\nevidence of catastrophic fatigue failure within the tested ranges. Notably, repeated\nstretching–release cycles result in a modest increase in micropillar aspect ratio, while\ntactile loading induces a more pronounced increase, with the aspect ratio rising from\n~0.94 to ~1.43. This behavior is enabled by the compliant deformation of the\nelastomeric micropillars, which accommodate repeated mechanical interactions\nthrough reversible bending and compression rather than material damage. As a result,\nthe evolution toward higher-aspect-ratio Braille features is favorable for tactile\nperception, indicating that repeated use within the tested cycle range does not lead to\nfunctional degradation of the Braille training platform. It should be noted, however,\nthat under much longer-term use involving tens or hundreds of thousands of tactile\ncycles, wear and material degradation of elastomeric substrates are expected to become\nunavoidable.” has been revised.\nAdditional Figures (Supplementary Fig. 28 and Fig. 29) and corresponding\ncaptions have been added to the revised supplementary information.\nWe sincerely thank the reviewers for the constructive and insightful comments,\nwhich have helped us significantly improve the scientific rigor, clarity, and overall\nimpact of this manuscript. We hope that the revisions and additional analyses\nadequately address the reviewers’ concerns and that the revised manuscript now meets\nthe required standards.\n1. Park, S., et al., Silicones for stretchable and durable soft devices: Beyond Sylgard-184. ACS\napplied materials & interfaces, 2018. 10(13): p. 11261-11268.\n2. Gent, A.N., Engineering with rubber: how to design rubber components. 2012: Carl Hanser\nVerlag GmbH Co KG.\n3. Treloar, L.G., The physics of rubber elasticity. 1975.\n4. Qi, H.J. and M.C. Boyce, Stress–strain behavior of thermoplastic polyurethanes. Mechanics of\nmaterials, 2005. 37(8): p. 817-839.\n5. Arruda, E.M. and M.C. Boyce, A three-dimensional constitutive model for the large stretch\nbehavior of rubber elastic materials. Journal of the Mechanics and Physics of Solids, 1993.\n41(2): p. 389-412.\n6. Mensah, B., et al., Carbon nanotube-reinforced elastomeric nanocomposites: a review.\nInternational Journal of Smart and Nano Materials, 2015. 6(4): p. 211-238.\n7. Kumar, V., et al., Silicone rubber composites reinforced by carbon nanofillers and their hybrids\nfor various applications: A review. Polymers, 2021. 13(14): p. 2322.\n8. Watanabe, T., et al. Development of a measuring system of contact force during braille reading\nusing an optical 6-axis force sensor. in 2006 International Conference of the IEEE Engineering\nin Medicine and Biology Society. 2006. IEEE."}, {"round": 2, "reviewer_comments": {"reviewer_1": "This article can be accepted without changes.", "reviewer_2": "The authors have addressed my concerns and the manuscript is suitable for publication."}, "author_response": ""}]

Decision letter