Biocompatible circuit-breaker chip for temperature regulation of electrothermally driven smart implants

This paper presents a thermoresponsive micro circuit breaker for biomedical applications specifically targeted at implantable microsystems. The circuit breaker is micromachined to have a shape-memory-alloy cantilever actuator as a normally closed temperature-sensitive switch to protect the device of interest from overheating, a critical safety feature for smart implants including those that are electrothermally driven. The micro breaker is constructed using biocompatible materials in a form of 1.5×2.0×0.46 mm³ Ti-packaged chip and exhibits a cold-state resistance of 14 Ω. The chip functionality is tested in combination with a wireless resonant heater powered by radio-frequency electromagnetic radiation, demonstrating self-regulation of heater temperature. The developed breaker chip operates in a fully passive manner, contributing to the miniaturization of smart implants in which thermal management is essential.