Biocompatible circuit-breaker chip for thermal management of biomedical microsystems

摘要

This paper presents a thermoresponsive micro circuit breaker for biomedical applications specifically targeted at electronic intelligent implants. 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 with wireless micro heaters. The device is fabricated in a size of 1.5 x 2.0 x 0.46 mm(3) using biocompatible materials and a chip-based titanium package, exhibiting a nominal cold-state resistance of 14 Omega. The breaker rapidly enters the full open condition when the chip temperature exceeds 63 degrees C, temporarily breaking the circuit of interest to lower its temperature until chip temperature drops to 51 degrees C, at which the breaker closes the circuit to allow current to flow through it again, physically limiting the maximum temperature of the circuit. This functionality is tested in combination with a wireless resonant heater powered by radio-frequency electromagnetic radiation, demonstrating self-regulation of heater temperature. The developed circuit-breaker chip operates in a fully passive manner that removes the need for active sensor and circuitry to achieve temperature regulation in a target device, contributing to the miniaturization of biomedical microsystems including electronic smart implants where thermal management is essential.