Electrospinning is widely used for the manufacture of fibers in the low-micrometer to nanometer range, allowing the fabrication of flexible materials with a high surface area. A distinction is made between solution and melt electrospinning. The former produces thinner fibers but requires hazardous solvents; whereas the latter is more environmentally sustainable because solvents are not required. However, the viscous melt requires high process temperatures and its low conductivity leads to thicker fibers. Here, we describe the first use of the biobased dyes alizarin; hematoxylin and quercetin as conductive additives to reduce the diameter of polylactic acid (PLA) fibers produced by melt electrospinning; combined with a biobased plasticizer to reduce the melt viscosity. The formation of a Taylor cone followed by continuous fiber deposition was observed for all PLA compounds; reducing the fiber diameter by up to 77% compared to pure PLA. The smallest average fiber diameter of 16.04 µm was achieved by adding 2% (w/w) hematoxylin. Comparative analysis revealed that the melt-electrospun fibers had a low degree of crystallinity compared to drawn filament controls—resembling partially oriented filaments. Our results form the basis of an economical and environmentally friendly process that could ultimately, provide an alternative to industrial solution electrospinning

Sub-microfibers are polymer filaments less than 1 µm in diameter that can be fabricated into highly flexible materials with a large specific surface area. They are often produced by solvent or melt electrospinning. The former is a scalable process that produces thinner fibers but requires hazardous solvents, whereas the latter is more environmentally sustainable due to the absence of solvents but is more challenging to scale up. Here we investigated the manufacturing of biobased polylactic acid (PLA) sub-microfibers by melt electrospinning using a single-nozzle laboratory-scale device and a novel 600-nozzle pilot-scale device combined with conductive and viscosity-reducing additives: sodium stearate (NaSt), sodium chloride (NaCl) and a polyester-based plasticizer. We determined the effect of different additive concentrations on fiber diameter, thermal properties, polymer degradation, and fiber deposition. At the laboratory scale, the minimum average fiber diameter (16.44 µm) was accomplished by adding 2% (w/w) NaCl, but a stable spinning process was not achieved and the plasticizer did not reduce the melt viscosity. NaSt was the most effective additive in terms of adapting the material properties of PLA for melt electrospinning, but extensive polymer degradation occurred at higher temperatures and with higher concentrations of the additive. At the pilot-scale, the minimum average fiber diameter (3.77 µm) was achieved by adding 6% (w/w) NaSt, with a spinneret temperature of 195℃ and a spin pump speed of 0.5 rpm (0.16 cm3), without further improvements such as the integration of a heating chamber. The smallest single-fiber diameter (1.23 µm) was achieved under the same conditions but using a spin pump speed of 2 rpm. The scaled-up melt-electrospinning device therefore offers significant potential for the production of biobased sub-microfibers, bridging the gap between laboratory-scale and pilot-scale manufacturing.