Overcoming Silk Fibroin Electrospinning Limitations: Ultra-High Surface Area Nanofibers and Microfilms Through Ethyl Cellulose-Assisted High-Speed Spinning

Abstract

Silk fibroin (SF) is a fundamental building block for the development of advanced biomaterials. SF nanofibers are ideal for industrial and biomedical applications due to their excellent biocompatibility, mechanical strength, and tunable biodegradability. However, conventional electrospinning suffers from jet instability, low fiber yield, and poor spinnability, which restricts its performance and scalability. In this study, we present a high-speed, controllable electrospinning process coupled with a simple, environmentally friendly post-treatment using ethanol. SF nanofibers were produced by blending SF with ethyl cellulose (EC), a naturally derived biocompatible polymer. The addition of EC significantly enhanced the viscoelasticity of the spinning solution, enabling the continuous electrospinning of EC-SF composite fibers. This method facilitated the high-yield production of EC-SF composite fibers, offering industrial-level scalability (10 mL/h per needle) and efficiency compared to lab-scale low-SF electrospinning techniques. A key innovation of this approach is the complete removal of EC via simple ethanol washing, which exploits EC's rapid solubility in ethanol to produce large quantities of pristine ultrathin SF nanofibers (average diameter: ~90 nm) with an ultrahigh surface area (BET: 78.82 m²/g)—notably, replacing ethanol with an ethanol-water mixture during post-treatment induced EC-SF microfilm formation, driven by insufficient EC solvation, which triggers gelation and subsequent rearrangement of the SF nanofibers into a network. These results confirm the tunability of our approach for generating a variety of SF-based architectures. As such, this work demonstrates a stable and eco-friendly method for fabricating SF-based composite fibers, EC-SF microfilms, and pure SF nanofibers, thereby eliminating the need for non-biodegradable synthetic polymer carriers or toxic crosslinkers. The simplicity, versatility, and sustainability of this approach offer strong potential for industrial-scale applications in biomedical engineering, filtration, and advanced materials.