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With potential applications in medical devices and advanced sensors, the multifunctional material was developed by researchers at Imperial College London, Tufts University in Massachusetts and the University of Michigan.
The work demonstrated that aligned silk fibres can be fused using heat and pressure alone, avoiding the large amounts of solvent normally required to process them. The new process preserves the natural hierarchical structure that gives silk its strength, optical properties and biocompatibility.
“Silk is extraordinary because its performance comes from a finely tuned structure that has evolved over millions of years,” said research co-leader Emiliano Bilotti, associate professor at Imperial.
“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.”
In the study, the team developed a rapid thermo‑mechanical process in which aligned, degummed silk fibres are hot‑pressed at defined temperatures and pressures. 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,” Bilotti said. “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 testing showed that the fused silk materials outperform previous silk‑based bulk materials and can compete with established structural materials. The researchers measured flexural strengths of up to 510 megapascals and flexural moduli of 21.5 gigapascals. When stretched, the material had a toughness approaching Kevlar fibres, surpassing typical values 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 Professor Nicholas A Kotov from 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.”
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,” Kotov said. “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. “Depending on how we process the silk, we can design materials that either integrate gradually with tissue or remain stable for long‑term support.”
The work was published in Nature Sustainability.
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