Silk Cooling Textile That Helps Skin Stay Cooler

Topic: sustainable textiles, radiative cooling fabric, silk fibroin nanofiber, personal thermal management

As heat waves become more frequent, cooling clothing is moving from a seasonal comfort feature to a serious material challenge. A new all-silk textile, known as SilkNT, shows how natural fibers can be engineered for passive radiative cooling without relying on petroleum-based polymers or inorganic nanoparticles.

Many high-performance cooling fabrics use materials such as PTFE, PVDF, titanium dioxide or alumina particles to reflect sunlight and release body heat. These approaches can work, but they may also raise concerns about microplastic release, nanoparticle shedding and end-of-life waste. SilkNT takes a different path: it uses silk itself as the functional cooling material.

Key performance highlights reported by the research team:

94.8% solar reflectance and 96.3% infrared emittance.
About 4.3°C lower skin temperature than ordinary silk in a real wearing test.
Up to 8.3°C, 9.0°C and 8.0°C additional cooling compared with silk, acetate and cotton in a heated skin-simulator test.
Biodegradable, recyclable and free from plastic or inorganic nanoparticle additives.

94.8%solar reflectance

96.3%infrared emittance

4.3°Clower skin temperature vs. ordinary silk

95%reported recycling rate

Why Cooling Fabric Needs a Cleaner Material Strategy

Radiative cooling textiles work by reflecting incoming solar energy and emitting heat through the atmospheric infrared window. For clothing, the ideal fabric must do more than cool the surface. It also needs to feel comfortable, handle sweat, survive washing, avoid irritating the skin and reduce environmental impact after disposal.

This is where conventional solutions often face a trade-off. Synthetic polymers and nanoparticle coatings can improve cooling performance, but they can complicate biodegradation and may release unwanted particles during wear and laundering. A sustainable cooling fabric needs strong optical performance and a cleaner life cycle.

What Is SilkNT?

SilkNT is an all-silk nanofiber textile developed by researchers from Tsinghua University and Northeast Forestry University, with collaborators from other institutions. The concept starts with ordinary silk yarn, then wraps it with regenerated silk fibroin nanofibers through a Fermat-spiral twisting method. The result is a core-shell silk yarn that can be woven into a hierarchical micro-nano textile.

This structure matters because natural silk fibers are usually around the micrometer scale and do not scatter sunlight strongly enough on their own. By adding a network of silk fibroin nanofibers with diameters around the visible-light wavelength range, the fabric scatters more sunlight across the solar spectrum. In practical terms, the textile stays whiter, reflects more heat from the sun and reduces heat absorption.

How Silk Reflects Sunlight and Releases Heat

Silk fibroin has two useful optical traits. First, it absorbs very little in much of the solar spectrum. Second, its refractive index helps the nanofiber network scatter incoming light. When the nanofiber size is tuned close to the wavelength of sunlight, scattering becomes much more efficient.

The research also highlights a photonic conversion effect: silk fibroin can convert part of the ultraviolet light into visible light emission. This helps reduce heat buildup caused by ultraviolet absorption. Together, the nanofiber geometry, low solar absorption and infrared emission give SilkNT its passive daytime radiative cooling performance.

Outdoor Cooling Performance

In outdoor tests using a skin simulator, SilkNT kept the covered surface below ambient temperature under strong midday sunlight. Ordinary silk, by contrast, showed a higher surface temperature than the surrounding air in the same type of comparison.

To better simulate real body heat, the researchers also applied a continuous heat input of 100 W m^-2. Under this condition, SilkNT delivered additional cooling of 8.3°C compared with regular silk, 9.0°C compared with acetate and 8.0°C compared with cotton. Compared with bare simulated skin, the temperature reduction reached 18.4°C.

In a wearing test, SilkNT was inserted into a regular silk T-shirt. After one hour under sunlight, the skin area covered by SilkNT was about 4.3°C cooler than the area covered by ordinary silk. Infrared thermal imaging also showed a visible temperature difference on the garment surface.

Comfort, Durability and Skin Compatibility

A cooling textile must still behave like a textile. According to the reported data, the Fermat-spiral twisting process preserved useful mechanical strength and stretchability. Because the material remains silk-based, it also supports moisture absorption and moisture transport, which are important for hot-weather wear.

Wash stability is another practical advantage. After a standard washing cycle, the fabric maintained nearly all of its solar reflection ability. Even after extended washing, the reflectance stayed above 95% in the reported test. Cell-culture results also showed good biocompatibility compared with nanoparticle-enhanced cooling textiles.

Biodegradable, Recyclable and Designed for a Lower Impact

One of the strongest points of SilkNT is that the entire textile is made from silk. In enzymatic degradation tests, the material gradually broke down over time, with roughly one-third mass loss after 365 days. In soil, it degraded faster than several common synthetic polymers such as PVDF-HFP, polyethylene, PTFE and nylon.

The material can also be recycled through established silk fibroin recovery processes. The study reports a recycling rate of about 95%, allowing the recovered silk to be processed again into cooling textile material. Life-cycle assessment further suggests lower environmental burdens than nanoparticle-coated or nanoparticle-embedded cooling fabrics across several impact categories.

Where This Technology Could Go Next

SilkNT is still a research-stage textile, not a mass-market garment. Even so, the material strategy points toward a promising direction for sustainable personal thermal management. It combines passive cooling, natural-fiber comfort, biodegradability and recyclability in one platform.

Beyond summer clothing, the same design logic may inspire building facade textiles, vehicle covers, agricultural shade fabrics and other low-carbon thermal management materials. As cities face hotter summers and higher cooling demand, fabrics that reduce heat without extra energy use could become an important part of sustainable design.

Conclusion

SilkNT shows that high-performance cooling does not have to depend on plastic-rich or nanoparticle-heavy systems. By engineering silk at the micro and nano scale, researchers created an all-silk radiative cooling textile with strong solar reflectance, high infrared emittance, real on-body cooling, wash stability, biocompatibility, biodegradability and recyclability.

For brands and material developers working on sustainable apparel, passive cooling fabric and next-generation natural fibers, this research offers a clear signal: the future of cooling textiles may be lighter, cleaner and closer to nature than expected.