Cryogel‐Based Electronic–Tissue Interfaces with Soft, Highly Compressible, and Tunable Mechanics

• Published in: Macromolecular materials and engineering Vol. 304; no. 12
• Main Authors: Ghatee, Rosa, Tolouei, Anita, Fijalkowski, Jennifer, Alsasa, Abdulrahman, Hayes, Justin, Besio, Walter, Kennedy, Stephen
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01.12.2019
• Subjects: Compressibility; Conducting polymers; conductive polymers; Crosslinking; Electric components; Electrical resistivity; electrodes; Fibroblasts; Freezing; Hydrogels; Implantation; Mechanics; Mechanics (physics); Needles; Neural prostheses; neuroprosthetics; Polyacrylic acid
• ISSN: 1438-7492; 1439-2054
• DOI: 10.1002/mame.201900367

Electrically conductive materials with soft, tough, and tunable mechanics have utility in a wide range of applications including neuroprosthetics. Such materials can serve as interfaces between electrical components and tissues, providing mechanical matches with and better conformations to soft, irregularly shaped surfaces. Hydrogels can potentially provide these attributes while remaining hydrated for long periods of time—providing a long‐term and stable electronic–tissue interface. Additionally, in applications that demand implantation, hydrogels can be formulated to locally deliver enhancing therapeutics. Here, hydrogels are developed by entrapping a conducting polymer within a crosslinked poly(acrylic acid) (pAAc) network. Critically, these hydrogels are cast under freezing conditions which produces cryogels that exhibit macroporous, soft, and highly tunable mechanics (0.2–20 kPa, by varying pAAc and crosslinker concentrations). Additionally, these cryogels are tough enough to survive over 90% compression, which enables survival after being passed through 16‐gauge needles. Cryogels also exhibit electrical conductivities that are sufficient to record alpha waves from the scalp of human subjects. Growth of fibroblasts cultures in the presence of these cryogels produce statistically similar viabilities compared to controls and do not disrupt fibroblast cell cycles. Finally, cryogels are capable of being loaded with and delivering proteins that can potentially combat inflammation. Poly(3‐4, ethylenedioxythiophene) (PEDOT)‐integrated cryogels exhibit porous, soft, and highly compressible mechanics and can electrically transmit neural signals. PEDOT cryogels exhibit macroporous structures that enhance softness and compressibility which enables injection through a 16‐guage needle. Cryogel conductivity is sufficient to record EEG signals at levels similar to traditional conductive pastes.