Tuning the electrochemical response of PCL-PEDOT:PSS fibers-based sensors by gas dissolution foaming

A new procedure to enhance the performance of polymer-based electrochemical sensors is proposed in this work. Polycaprolactone (PCL) electrospun fiber mats with tunable fiber morphology are functionalized with a conductive polymer (PEDOT:PSS) by a facile dip-coting process, providing them the necessary electrical conductivity to work as sensors. The modification of the fiber morphology is achieved by an enhanced gas dissolution foaming procedure, an environmentally friendly procedure that employs CO2 as blowing agent and takes advantage of recent advances that allowed extending such procedure to polymeric microfibers. Thus, the enhanced gas dissolution foaming approach was employed both before and after the coating of the fiber mats with PEDOT:PSS, producing in both cases hollow fibers with enhanced surface porosity and area, as well as increased diameter regarding the initial solid PCL fibers. The addition of PEDOT:PSS, both in solid and foamed PCL fibers, allows their use as sensors, as proved by cyclic voltammetry in a KCl solution, as well as calibrated with catechol solutions. Remarkable influence of the foaming procedure on the performance of the sensors have been found, proving by a detailed characterization that the foaming procedure applied after the PEDOT:PSS coating provides an enhanced sensoring response (i.e., increased signal, optimal linearity, decreased LOD) due to their superior surface area and optimal PEDOT:PSS distribution along the fiber mats, not only covering the external surface of the fibers but infusing into the inner regions.