Nanofibers prepared by electrospinning technique are extensively applied as building blocks for tissue-engineered scaffolds because of their high resemblance to natural extracellular matrix (ECM) and the capacity to provide more cell contacts than microfibers. However, conventional electrospun scaffolds only allow superficial growth of cells in that the size of inter-fiber pores is much smaller than the size of cells. By taking advantage of the positive correlation between fiber diameter and pore size in fibrous materials, we report here a simple method for fabricating poly-L-lactic acid (PLLA) microfiber scaffold with longitudinally aligned nanogrooves on fiber surface. Three-dimensional (3D) and structurally stable PLLA scaffolds with an average pore size of 16 μm were successfully acquired when the fiber diameter was 4.22 μm. The topographical cues from nanogrooves ensured fast cell adhesion of scaffolds, whilst the large inter-fiber pores enabled sufficient cell infiltration. Moreover, the nanogrooved microfiber scaffold showed improved curative effects of wound healing in a rat skin injury model, making us believe its practical significance in biomedical areas that requires fast cell adhesion and high cell infiltration.

Fiber morphology with off-standing branches, as found in nature, e.g., in goose downy feather, provides exquisite functions that can be barely achieved by man-made fiber systems. In this work, we develop a simple and scalable method for generating downy feather-like para-aramid fibers and assemblies. Through treating commercial para-aramid microfibers with mild alkaline solution (low concentration of NaOH), a synergistic effect of chemical hydrolysis and physical shearing is successfully triggered to generate abundant nanofiber branches on the surface of para-aramid fibers. When compared with conventional monotonous structures, nonwovens composed of downy feather-like fibers exhibit a typical multiscale fiber morphology, larger specific surface area and smaller pore size, thus showing enhanced particles adsorption capacity (over twice of the pristine nonwoven), excellent oil absorption capacity (increased by ~ 50%), improved air filtration performances (doubled the filtration efficiency) and effective thermal insulation (thermal conductivity = 26.1 mW·m⁻¹·K⁻¹). More attractively, the intrinsic flame-retardant nature of para-aramid is well inherited by the downy feather-like fibers, and the fabrication process requires neither sophisticated equipment, nor tedious procedures, making us believe the strong competitiveness of these fibers and assemblies.