Biocompatible low-voltage electrothermal actuators with biological operational temperature range.

Abstract

Muscle loss can severely affect movement and physiological functions, driving interest in artificial muscle development. Although various soft actuators exist, ensuring biocompatibility-especially in terms of heat transfer and non-cytotoxicity-remains a key challenge. To address these issues, here we develop Bio35, a low-voltage (3.6 V) electrothermal actuator that operates at mild hyperthermic temperatures (38.9 °C). Bio35 is synthesized using a one-pot, solvent-free process with Epikote 828, poly(propyleneglycol) bis (2-amino-propyl-ether) (PPG), and 1,4-diamino-diphenyl-sulfone (DDS). It demonstrates high chemical stability, maintaining actuation performance after more than 100 cycles over 200 min. Initial biological tests confirm that these materials are biocompatible and non-cytotoxic. As proof of concept, we demonstrate two systems: a simple gripper capable of holding objects up to 225 mg and a sphincter-like valve, showcasing its potential for use in treating conditions like urinary incontinence, where precise, muscle-like actuation is critical for function.