Soft Flexible Skin Conformable Nanocomposites as a Platform for Electroceutical and Orthopedic Applications

Designing biomimetic substrates and electrodes for bioelectronic devices with the necessary mechanical, electrical, and biological properties is critical considering the potential mismatch between soft tissue and rigid electronics, where incompatibility leads to decreased device performance, delamination, inflammation, and discomfort. There is an unmet engineering and clinical need for epidermal bioelectronics that are bioinert, can emulate host tissue mechanical properties, demonstrate low bulk resistivity, and are flexible and scalable. To address this shortcoming, this work describes innovations pertaining to the development of a hydrophilic, biocompatible nanocomposite comprised of carbon black (CB), polyvinyl alcohol (PVA), and glycerol for neuro-muscular and rehabilitative applications. We find that this materials platform (herein referred to as CB-AFTIDerm), comprised of 3 wt% PVA and 5 wt% glycerol, demonstrated superior biocompatibility (cytotoxic grade of 0), high flexibility (maximum of 140% stretchability and as low as 1% ∆R/R_o at 3.5-cm bending diameter), low electrical resistivity (as low as 0.6 Ω.cm), and electrical stability over a long-term duration (at 235 Ω in the lateral direction and between 300 Ω and 400 Ω in the transverse direction for a 24 h period). We find that the optimal CB concentration for our material platform is at 50% CB. We present examples for use in electroceutical therapy of chronic wounds and in orthopedic rehabilitation for monitoring joint angles. Achieving such results from a material, mechanics, biological, and electrical perspective facilitates the translational potential of this materials platform for the digital health and wearable technologies community to improve patient outcomes.