Examination of the effects of dimethyl sulfoxide on PEDOT: PSS-based materials used in thermoelectric power systems developed for intracorporeal active implanted devices

Abstract

With the increasing use of active implantable medical devices (IMDs), studies to meet their energy needs have focused on wireless energy transfer and thermoelectric generators. Materials, which are one of the most critical research topics in thermoelectric power systems, are expected to have low thermal conductivity and high electrical conductivity. Recently, organic polymers, especially poly (3,4- ethylenedioxythiophene) poly styrene sulfonate, have been preferred due to concerns over the toxicity of inorganic materials. However, using solvents such as dimethyl sulfoxide to prepare high-concentration solutions of poly (3,4- ethylenedioxythiophene) poly styrene sulfonate (PEDOT: PSS) may raise biocompatibility issues. This study investigates the effects on electrical conductivity, Seebeck coefficient, and biocompatibility after mixing different dimethyl sulfoxide solutions with PEDOT: PSS. As a result of these analyses, the highest electrical conductivity, 156.15 S/cm, was achieved with a 15/85 (v/v) dimethyl sulfoxide-water solution. The highest Seebeck coefficient was obtained at 26.27 µV/K for the film prepared with a 10/90 (v/v) dimethyl sulfoxide-water solution. Biocompatibility tests were performed according to ISO 10993-5 and ISO 10993-12 standards with the L929 cell line. It revealed that higher dimethyl sulfoxide (DMSO) ratios lead to increased toxicity in PEDOT: PSS samples. Furthermore, the group with the highest biocompatibility, which shows over 70% cell viability even at a 1:1 (v/v) extract ratio, was found as the group with a 1:1 extract ratio that contains 1% PEDOT: PSS. These findings provide insights into optimizing PEDOT: PSS formulations for enhanced electrical performance while maintaining biocompatibility, contributing to the development of safer and more efficient thermoelectric power sources for implantable medical devices.