3D Printed Flexible Microscaled Porous Conductive Polymer Nanocomposites for Piezoresistive Sensing Applications

Porous conductive polymer nanocomposites (CPNCs) have attracted significant attention for developing flexible piezoresistive sensors. In this work, a novel approach is developed by combining direct ink writing (DIW) and solvent evaporation induced phase separation method to synthesize porous CPNC with strain sensing capabilities. CPNC is prepared by dispersing carbon nanotubes (CNTs) at various concentrations in polydimethylsiloxane polymer, followed by mixing with solvent and nonsolvent phases to achieve a homogenous solution. 3D structures with 100% infill density are deposited layer-by-layer via DIW, while a microscaled porous network is formed during the curing cycle. The phase separation is induced by solvent evaporation, followed by the nonsolvent phase, while the polymer experiences gelation during the heat treatment procedure. The microstructure of the printed samples is characterized utilizing a scanning electron microscope. The piezoresistive and mechanical behavior of porous CPNC is evaluated to identify the optimum formulation that provides the highest sensitivity and flexibility. The sensors made with 1 wt% CNT loading with the optimum printing conditions are then fully characterized to evaluate the durability and reliability of the 3D printed sample for long-term piezoresistive applications. The porous CPNCs are successfully employed as a piezoresistive sensor to detect human motion.