Spray techniques for controlled paper formation and stabilisation of microfibrillated silk

Microfibrillated silk (MFS) is a promising biobased fibre material; however, it is typically produced as a low solid content aqueous suspension and processed into papers via casting or vacuum filtration. Its liquid form poses challenges for handling, storage, and transport, and restricts processing to water-based systems only, limiting broader application potential. This work investigates the feasibility of spraying MFS for two objectives: first, to develop a spray-based approach for producing silk papers that avoids conventional time-consuming and water-intensive processes; and second, to generate a dry MFS powder for easier storage and transport, enabling subsequent redispersion in both water- and non-water-based systems. Spray coating enabled rapid formation of strong MFS papers through higher solids deposition and reduced drying times. For the second objective, spray drying was shown to be a feasible route to producing MFS powder, depending on fibril size. The resulting powders consisted of spherical aggregates of silk microfibrils. Upon redispersion in water under shear, the microfibrils reopened to form stable dispersions like the native suspension. Papers cast from redispersed suspensions exhibited properties comparable to those made directly from native suspensions. This demonstrates a route for long-term storage and on-demand processing of MFS, enhancing its commercial and sustainable processing potential.