Structural and Functional Characterization of Ultrasonically Treated PLA-PEDOT:PSS Nonwoven Composites for Soft Implantable Bioelectronics

Flexible implantable electrodes require biocompatibility, mechanical stability, and sufficient electrical conductivity for effective neural interfacing. This work examines ultrasonic treatment during poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) impregnation of electrospun poly(D,L)-lactide (PLA) nonwoven scaffolds as a route to improve filler distribution and functional performance. Four sample types were studied: pristine PLA (untreated and sonicated) and PLA–PEDOT:PSS composites prepared with and without ultrasonication. Scanning electron microscopy shows that ultrasonic treatment suppresses the formation of continuous surface films and promotes homogeneous three-dimensional penetration of PEDOT:PSS throughout the fibrous network. As a result, electrical resistivity decreases by a factor of 7.3, from 294.4 to 40.2 Ω·m. Contact-angle measurements reveal markedly enhanced wettability, with sonicated composites exhibiting rapid water uptake (5–13 s), unlike non-sonicated controls. These findings demonstrate that ultrasound-assisted PEDOT:PSS impregnation yields conductive, highly wettable, and structurally stable scaffolds, highlighting their potential for flexible implantable neural electrodes.