The study, published in the journal Advanced Composites and Hybrid Materials, describes a porous composite membrane made from hexagonal boron nitride (hBN) nanoplatelets embedded in polydimethylsiloxane (PDMS), the soft silicone elastomer that dominates skin-wearable design. The key innovation lies in how the pores are created. Instead of templating, washing, solvent extraction, or any post-fabrication treatment, the researchers mixed a volatile liquid, perfluorohexane (PFH), directly into the hBN/PDMS formulation. As the membrane was cast and cured, the PFH evaporated on its own, leaving behind a stable network of air voids. The porous architecture emerges during curing itself, which means the process can in principle run as a continuous, one-step casting operation without extra processing stages that add cost and complexity.

What makes the approach more than a convenience is the degree of control it offers. The team found that pore size could be tuned simply by changing the curing temperature, because temperature governs a kinetic race between two competing processes: the solidification of the PDMS matrix and the volatilization of the PFH porogen. When curing outpaces evaporation, the growing polymer locks in a particular pore morphology; when evaporation dominates, the voids evolve differently. By adjusting this balance, the researchers could dial in the porous structure without changing the chemistry of the formulation. Meanwhile, the overall porosity of the membrane rose from roughly 15 percent to about 31 percent as the PFH content in the mixture increased, giving a second, independent handle on the material’s internal architecture.

The central surprise of the work is thermal. Porosity normally kills thermal conductivity, since air-filled voids interrupt the paths along which heat travels. Yet the porous hBN/PDMS membrane achieved a thermal conductivity of 0.22 watts per meter-kelvin, essentially matching the dense form of the same composite. The explanation lies in how the hBN nanoplatelets arrange themselves during fabrication. Rather than being distributed randomly through the bulk, the platelets assemble along the walls of the pores, forming continuous heat-conduction pathways that thread through the material. Heat entering the membrane finds an interconnected skeleton of thermally conductive boron nitride to follow, even as the voids between those pathways remain open for water vapor transport. Breathability and heat dissipation, usually opposing goals, are satisfied simultaneously by the same microstructure.

To understand this behavior in more detail, the researchers turned to computational fluid dynamics simulations. The modeling showed that heat is transferred more effectively near the interface between the hBN and the PDMS matrix in the porous membrane than in comparable dense structures. That computational picture matched what the team observed experimentally: the porous membrane accumulated less heat during use. In a skin-interface application, lower heat accumulation translates directly into less thermal stress on the tissue beneath, which matters both for user comfort and for the accuracy of sensors that measure physiological signals through the skin.

Thermal performance alone would not make a material suitable for wear. The team therefore evaluated the membrane in contact with living skin. In vivo analysis showed that the porous membrane kept skin hydration at a stable level of approximately 103 to 107 percent over the testing period, indicating that the material does not trap moisture against the skin or dry it out. Hydration stability is a meaningful benchmark for wearables, because occlusive films that block vapor transport cause the skin to macerate over time, degrading both comfort and measurement quality. A membrane that holds hydration in a narrow, healthy band addresses one of the most common complaints about long-duration skin patches.

Mechanical compliance proved equally convincing. The porous membrane’s mechanical behavior was found to be close to that of bare skin, meaning the material deforms in a way that the body does not register as a stiff foreign object. This is where the choice of PDMS as the matrix pays off: the elastomer is soft, stretchable, and biocompatible, and introducing controlled porosity pushes its effective stiffness even lower. Combined with the hydration results, the mechanical data suggest that the membrane satisfies both the physiological and mechanical criteria for comfortable, extended skin contact, which the authors describe as the foundation for future skin-interface applications.

The significance of the work extends beyond a single material recipe. Hexagonal boron nitride is prized in electronics for its thermal conductivity, electrical insulation, and chemical stability, and pairing it with PDMS is a natural strategy for thermally managed wearables. What has been missing is a fabrication route that preserves those thermal benefits while adding breathability without extra processing. By using a volatile porogen that does its job and disappears during curing, the researchers have effectively turned the manufacturing step itself into the design tool. The pore structure, the porosity, and the platelet alignment all emerge from the interplay of curing kinetics and evaporation, parameters that are easy to adjust on a production line.

The study was a collaboration between the Research and Innovation Center of Amorepacific Corporation in Yongin and the School of Mechanical Engineering at Soongsil University in Seoul, combining industrial materials expertise with mechanical engineering analysis. The work was supported by South Korea’s National Research Foundation through its Bio and Medical Technology Development Program and the G-LAMP Program, as well as by the Ministry of Trade, Industry and Energy through an Industrial Technology Innovation Program grant. The involvement of a major cosmetics and personal care company hints at near-term applications in skin patches, cosmetic films, and health-monitoring wearables, where thermal comfort and moisture management directly affect product performance.

For the wearable industry, the message is that the long-standing trade-off between breathability and thermal management may be an artifact of how porous materials have been made, not a law of physics. If thermally conductive fillers can be guided to line the pore walls of a soft elastomer, air voids no longer have to be thermal dead ends. The one-step PFH porogen method offers a scalable route to that architecture, with tunable pores, no washing or extraction stages, and demonstrated comfort on living skin. As skin-interfaced sensors, electronic skins, and on-body therapeutic devices multiply, materials like this porous hBN/PDMS membrane could determine whether the next generation of wearables is something people actually forget they are wearing.

Subject of Research: One-step fabrication of porous hexagonal boron nitride/PDMS composite membranes for breathable, thermally dissipative skin-interface wearable applications

Article Title: One-step fabrication of a porous hBN/PDMS composite membrane for breathable and thermally dissipative skin-interface applications

Article References: Lee, J. Y., Lee, S. K., Nam, J., & Hong, J. (2026). One-step fabrication of a porous hBN/PDMS composite membrane for breathable and thermally dissipative skin-interface applications. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02120-y

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02120-y

Keywords: hexagonal boron nitride, PDMS, porous membrane, thermal management, breathability, wearable electronics, skin-interface materials, perfluorohexane porogen, thermal conductivity, skin hydration, mechanical compliance, computational fluid dynamics

The central problem the KAIST group, led by corresponding author Ki-Uk Kyung, attacked is one that anyone who has dragged a fingernail across a chalkboard will recognize intuitively. When two surfaces in contact begin to slide, friction does not behave politely. Static friction, the force that must be overcome to start motion, is typically higher than kinetic friction, the force that resists motion once sliding is underway. In an electrostatic clutch, where voltage presses two films together and controls how much shear force the interface can transmit, this disparity produces the notorious stick–slip instability: the interface grabs, builds up elastic strain, breaks loose, snaps forward, and grabs again, cycling hundreds of times per second. The result is a vibration that ruins precision and, worse, makes the transmitted force effectively binary. Most electrostatic clutches reported to date can only be commanded fully on or fully off, which is a poor match for robots that need to modulate stiffness continuously, the way a human hand modulates its grip.

The KAIST team’s answer lies in the choice of dielectric. Conventional electrostatic clutches sandwich ordinary insulating films between electrodes, relying on simple capacitive attraction to press the surfaces together. The new device instead uses a plasticized polyvinyl chloride gel, a soft polymer material with an unusual electrostatic property: when a voltage is applied, charges accumulate at the interface between the gel and the electrode rather than merely sitting on capacitor plates. This interfacial charge accumulation generates electrostatic pressures far beyond what a conventional dielectric of the same thickness can produce. The numbers reported in the paper are striking. The device achieves a shear stress capacity of approximately 29 newtons per square centimeter at just 100 volts. For comparison, typical electrostatic clutches in the literature require driving voltages in the kilovolt range to reach comparable force densities, which means heavy insulation, bulky high-voltage supplies, and serious safety considerations for any wearable application.

Force alone, however, would not have been enough, and this is where the materials science becomes genuinely clever. The researchers systematically tuned the amount of plasticizer blended into the PVC gel, discovering that the formulation affects not just the magnitude of the electrostatic force but the entire dynamic character of the friction. The optimized composition does two things simultaneously. First, it minimizes the gap between static and kinetic friction, so the interface no longer has a strong incentive to grab and release cyclically. Second, it induces a velocity-strengthening friction response, meaning that as the sliding speed increases, the friction force rises rather than falls. That behavior is dynamically stabilizing: any tendency of the interface to accelerate is met with increasing resistance, which damps the oscillation that would otherwise grow into stick–slip. The combination ensures continuous, judder-free sliding even while the interface is transmitting substantial shear loads.

The practical payoff is quantified in the paper’s headline demonstration: precise control of kinetic friction while the device carries a shear stress of 22.5 newtons per square centimeter. In other words, the clutch can hold a heavy load, then release it into smooth, metered sliding, all under low-voltage electronic command. Because the friction can be set continuously anywhere between locked and free rather than snapped between two states, the device functions as a true variable clutch. A robotic arm equipped with such an interface could stiffen its joints to manipulate a heavy object, soften them the instant it detects an unexpected collision, and modulate the transition smoothly enough that neither the robot nor whatever it touches experiences a jolt. Programmable mechanical compliance of this kind is exactly what safety standards for collaborative robots have been pushing the industry toward.

To show the mechanism is more than a laboratory curiosity, the team validated it across three distinct robotic control scenarios. The first is programmable impact damping: by electronically setting the friction level, the device can absorb and dissipate impact energy on demand, acting like a shock absorber whose damping curve is written in software rather than cast into a viscous fluid. The second is the variable clutch itself, where the modulator couples and decouples mechanical power transmission with continuously adjustable strength. The third, and perhaps the most immediately tangible for consumers, is a wearable haptic device. Because the thin film is lightweight and operates at 100 volts rather than several kilovolts, it can plausibly be integrated into a glove or sleeve, rendering realistic tactile sensations by varying the friction a user’s fingertip experiences as it strokes a surface, from slick ice to gritty sandpaper.

The low-voltage operation deserves particular emphasis because it changes the engineering envelope of the whole field. High-voltage electrostatic clutches have historically been confined to tethered laboratory setups, with isolation circuitry that makes them impractical for mobile robots or battery-powered wearables. Dropping the drive requirement by more than an order of magnitude means the clutch electronics can shrink toward the scale of the display drivers and motor controllers already embedded in commercial robots. The thin-film form factor compounds the advantage: the modulator adds negligible mass and can conform to curved joint surfaces, in contrast to electromagnetic clutches whose copper windings and steel cores concentrate weight exactly where a robot can least afford it, at the distal end of its limbs.

There is also a broader materials-science lesson embedded in the result. PVC gels have been studied for years as electroactive polymers, best known for creeping and deforming under high voltage in actuator demonstrations. This work reframes the material as a charge accumulator whose interfacial electrostatics can be engineered through formulation chemistry. The finding that plasticizer content governs the velocity dependence of friction, and through it the stability of sliding, connects polymer physics directly to a control problem that has limited electrostatic clutching for a decade. It suggests a design space in which tribological behavior, not just force output, becomes a tunable property of the material itself, opening the door to gels optimized for specific load ranges, sliding speeds, or environmental conditions.

The research, led by Jihyeong Ma, Jongseok Nam, and Nakhyeong Lee together with Kyung in KAIST’s Department of Mechanical Engineering, was supported by the National Research Council of Science and Technology, the Institute of Information and Communications Technology Planning and Evaluation, and the National Research Foundation of Korea. The authors report no competing interests, and the paper is open access, with supplementary videos documenting the damping, clutching, and haptic demonstrations. If the stick–slip-free performance holds up under the wear, temperature swings, and millions of duty cycles that real robots inflict on their components, the PVC-gel friction modulator could become a standard building block of a new generation of machines that are simultaneously strong, safe, and exquisitely adjustable, gripping the world with a firmness chosen moment by moment in software.

Subject of Research: PVC-gel electrostatic friction modulation for variable robotic clutches

Article Title: Thin-film dynamic friction modulator interfaced with PVC-gel charge accumulator for variable clutching of robotic systems

Article References: Ma, J., Nam, J., Lee, N., & Kyung, K.-U. (2026). Thin-film dynamic friction modulator interfaced with PVC-gel charge accumulator for variable clutching of robotic systems. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02056-3

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02056-3

Keywords: PVC gel, electrostatic clutch, friction modulation, stick-slip, soft robotics, haptics, variable clutch, mechanical compliance, interfacial charge accumulation, wearable devices, KAIST, electroactive polymers