Electrospun biodegradable polycaprolactone filter media for filtering facepiece respirators.

Filtering facepiece respirators (FFRs) protect against disease transmission and other harmful air pollutants through the collection of incident aerosolized particulates. Conventional disposable FFRs, featuring meltblown polypropylene filter layers, rely on electrostatic charges to achieve N95 performance and are not biodegradable. Electrospun filters can achieve high filtration performance without electrostatic charging due to their small fiber size and may be fabricated from environmentally degradable materials. In this work, we design filter media made of biodegradable poly(ε-caprolactone) (PCL) nanofibers electrospun from a relatively benign solvent system. These media meet N95 performance targets for filtration efficiency and inhalation and exhalation resistance under laboratory test conditions. Moreover, we demonstrate the fabrication of media having average fiber diameters between 60 nm and 300 nm, and we propose combinations of fiber diameter, solidity, and basis weight that produce filters meeting N95 targets. Our results indicate that selecting electrospun media with particularly small diameter fibers leads to better filtration performance with less material and enhanced rates of degradation. Using these insights, we fabricate prototype duckbill-style respirators featuring an electrospun PCL filter layer sandwiched between polylactic acid spunbond support layers. These prototypes meet the N95 criteria for filtration efficiency and breathing resistance under the tested conditions. Supplementary Information: The online version contains supplementary material available at 10.1007/s44493-026-00021-6.