Imperial-led team fuse natural silk into ultra‑strong, sustainable materials

Imperial College London researchers have developed a solvent free way to fuse natural silk fibres into strong, multifunctional solid materials using heat and pressure alone. Published in Nature Sustainability, the scalable process preserves silk’s natural structure, delivering mechanical performance similar to Kevlar while retaining optical and biological functionality for sustainable engineering and medical applications.

Imperial College London researchers have developed a simple, scalable way to transform natural silk fibres directly into strong, multifunctional solid materials, avoiding the large volumes of solvents normally required to process silk. 

The work, published in Nature Sustainability, demonstrates that aligned silk fibres can be fused using heat and pressure alone, preserving the natural hierarchical structure that gives silk its remarkable strength, optical properties and biocompatibility.  

Silk is best known as a delicate textile, yet at the level of individual fibres it is one of nature’s toughest materials, combining high strength, damage tolerance and resilience with optical and biological functionality. These properties have long made silk attractive for advanced technologies, and this new processing method opens new routes to sustainable, high‑performance materials for applications ranging from lightweight engineering and advanced optics to biodegradable medical devices. 

The research was co‑led by Emiliano Bilotti, Associate Professor in Multifunctional and Sustainable Polymer Composites in the Department of Aeronautics at Imperial, working with collaborators at Tufts University and the University of Michigan. 

“Silk is extraordinary because its performance comes from a finely tuned structure that has evolved over millions of years,” said Emiliano Bilotti. “Most advanced silk materials today are made by dissolving the fibres and rebuilding them, which disrupts that structure and carries a significant environmental cost. We wanted to see if we could keep silk as close as possible to its natural state, while still shaping it into useful, high‑performance components of arbitrary geometry.”  

Fusing fibres without chemical reprocessing 

High‑performance synthetic materials underpin technologies from healthcare and transport to electronics and communications, but their manufacture often depends on energy‑intensive processes and non‑renewable resources. Silk has long attracted interest as a sustainable alternative, combining mechanical robustness with optical functionality, biocompatibility and biodegradability. 

Most advanced silk‑based materials rely on dissolving silk fibres into solution before regenerating them into new forms. These processes use large amounts of water and chemicals, take days or weeks, and can erase the native multiscale organisation that underpins silk’s properties.  

In the new study, the team developed a rapid thermo‑mechanical process in which aligned, degummed silk fibres are simply hot‑pressed within a defined temperature and pressure window. Under these conditions, the naturally occurring amorphous regions of the silk proteins become mobile and diffuse across fibre boundaries, fusing neighbouring fibres together while leaving the ordered crystalline regions largely intact. 

“This is a purely physical process,” said Emiliano Bilotti. “By carefully controlling temperature and pressure, we can consolidate silk fibres into dense, transparent solids without additives or solvents, and without destroying the internal architecture that makes silk so tough.”  

Mechanical performance approaching Kevlar 

Mechanical testing showed that the fused silk materials outperform previously reported silk‑based bulk materials and compete with established structural materials. The researchers measured flexural strengths of up to 510 MPa, flexural moduli of 21.5 GPa and when stretched, the material had a toughness approaching that of Kevlar fibres, surpassing values typical of bone and wood. In impact tests, fused silk absorbed more energy per unit mass than a conventional carbon‑fibre‑reinforced polymer composite.  

“These results are remarkable for a bio‑derived material processed without solvents,” said Nicholas A. Kotov, Irving Langmuir Distinguished University Professor at the University of Michigan. “The key is that the crystalline regions and protein secondary structures inside the silk fibres are largely retained, allowing stress to be transferred efficiently across the material.”  

Our method can turn even small fibres into solid materials, which opens the door to more sustainable use of silk across its entire life cycle. Dr Emiliano Bilotti Associate Professor in Multifunctional and Sustainable Polymer Composites

Optical and biological functionality preserved

Beyond mechanical performance, the fused silk retained and, in some cases, amplified functional properties inherent to aligned silk fibres. The materials are transparent to visible light and twist the direction of the light’s vibration by a large amount, even when the material itself is thin. This has significant potential for use in the terahertz range, a frequency band of growing interest for future communications and imaging technologies. 

“It is very rare to find a material that is both transparent and capable of rotating terahertz light so strongly,” said Nicholas A. Kotov. “This could enable new types of components for terahertz optics and potentially future 6G communication systems.”  

The team also showed that the biological response of fused silk can be tuned through processing conditions. In studies in mice, implants produced at lower processing temperatures generated materials that allowed greater cell infiltration and faster biodegradation, while higher temperatures yielded more stable, slowly degrading implants.  

“This level of control is very attractive for medical applications,” said Chunmei Li, Research Assistant Professor at Tufts University. “Depending on how we process the silk, we can design materials that either integrate gradually with tissue or remain stable for long‑term support.”  

Towards circular silk manufacturing 

By enabling silk consolidation without dissolution, the work points to a lower‑footprint and more scalable manufacturing route for high‑performance bio‑derived materials. The researchers say the approach could broaden the use of silk from fibres to shaped components and support more circular strategies, such as upcycling end‑of‑life silk textiles into value‑added products.  

“At the moment, short or damaged silk fibres are often considered unrecyclable without dissolving them,” said Emiliano Bilotti. “Our method can turn even small fibres into solid materials, which opens the door to more sustainable use of silk across its entire life cycle.”  

The team is now exploring how to scale the process to larger and more complex shapes, alongside life‑cycle assessments to quantify the full sustainability benefits. The researchers are now seeking industrial and commercial partners to help scale the process and bring fused silk materials to market. They are also investigating functionalisation strategies that could turn fused silk into an active platform for sensing and other advanced applications.