Template-Directed Synthesis of Tissue-Like Conductive Hydrogels for Bioelectronics

Hydrogels are widely used in bioelectronics for the interfacing electrode between biology and electronics since they have tissue-like mechanical properties, high ionic conductivity, and biocompatibility. However, conventional hydrogels intrinsically have low electrical conductivity, which restricts efficient signal reading or stimulating. Several approaches have been made to improve electrical properties such as metallic fillers, carbon nanocomposite, and conductive polymers. Although metallic fillers and carbon materials gives good electrical properties, their size disparity with hydrogel networks leads to inhomogeneity and many of them are found to be cytotoxic. Therefore, conductive polymers are preferred in bio applications. Among them, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) have attracted extensive attention due to their high biocompatibility and high conductivity. Although PEDOT:PSS based hydrogel is a promising candidate for conductive hydrogel, high electrical conductance and tissue-like mechanical properties, such as high stretchability and low Young’s modulus, cannot be obtained simultaneously.<br/><br/>Here, we show a template-directed synthesis of PEDOT:PSS hydrogel that exhibits record-high conductivity (130 S/cm), high stretchability (&gt; 150%), tissue-like Young’s modulus (50~350 kPa), and high water content (&gt; 90%). The template polymer, which can be made of various hydrophilic polymers, forms the main body of the hydrogel and traps PEDOT:PSS colloidal solution. We developed a new synthetic route to assemble PEDOT:PSS colloids into highly conductive fiber network in template polymer. Then a highly conductive, stretchable and tissue-like soft hydrogel is achieved. Since our method is based on photopatternable polymer network, we successfully patterned our PEDOT:PSS hydrogel and fabricated intrinsically stretchable electrode array. In my presentation, I will discuss more details for hydrogel synthesis and their bioelectronic applications.