Reversibly Gellable Conductive Polymers for Minimally Invasive Electronics

• Casey Lorch, Biomedical Engineering, University of Delaware

• Laure Kayser, Materials Science, University of Delaware

Reversibly Gellable Conductive Polymers for Minimally Invasive Electronics

Casey Lorch¹, Vidhika Damani², Laure V. Kayser^2,3

Department of Biomedical Engineering

Department of Materials Science and Engineering

Department of Chemistry and Biochemistry

Innovations in medical technology present exciting avenues to revolutionize how we practice modern medicine. Hence, the use of biocompatible materials which mimic physical characteristics of natural tissues such as conductivity, softness and stimuli-response has become increasingly important to  interface medical devices with the human body.  One such material is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), a conductive polymer that can be introduced to tissues without rejection by the immune system. The conductive capabilities of this material mean that it could transmit vital electrical signals traveling through tissues that have been damaged or otherwise functionally impaired. However, PEDOT:PSS is not inherently stimuli-responsive. The Kayser lab has recently developed and patented a new derivative of the PEDOT:PSS by altering the PSS chain and synthesizing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate-block-poly(N-isopropylacrylamide), or PEDOT:PSS-block-PNIPAM. NIPAM is known to be thermo-responsive at 32-35℃, transitioning reversibly from hydrophilic to hydrophobic when heated above this temperature range. The addition of the PNIPAM block triggers the formation of a gel above 35℃ while being capable of reverting to a viscous liquid once cooled. With typical room temperature being 20℃ and body temperature being 37℃, it is our hope that this novel material may be used for minimally-invasive tissue regeneration via injection and gelation within hard-to-reach tissues. Since its development, we have begun to research methods for altering the mechanical properties of the gel. In synthesis for both our copolymer chain and PEDOT gel, we have optimized specific components such as reactant mass ratios, stir rate, reaction time, and water content. As more is learned about how these factors affect synthesis on a greater scale, mechanical properties of the gel may be tuned. Applications for our material could then include bioprinting scaffolds for specific, complex tissue structures as well as electronic interfaces for minimally invasive injectable devices.