Polysilicon-based flexible temperature sensor for brain monitoring with high spatial resolution

Temperature is one of the most important variables in brain monitoring, since changes of focal brain temperature are closely coupled to cerebral physiology and pathophysiological phenomena in injured brain. In this work, a highly accurate temperature sensor with polysilicon thermistors has been developed on flexible polyimide for monitoring brain temperature with high spatial resolution. The temperature sensors have a response time of 1.5 s and sensitivity of -0.0031 degrees C-1. Thermal hysteresis of the sensor in the physiological temperature range of 30-45 degrees C was found to be less than 0.1 degrees C. With silicon nitride as the passivation layer, the temperature sensor exhibits drift of less than 0.3 degrees C for 3 d in water. In vivo tests of the sensor show a low noise level of 0.025 +/- 0.03 degrees C, and the expected transient increases in cortical temperature associated with cortical spreading depolarization. The temperature sensor developed in this work is suitable for monitoring brain temperature with the desired high sensitivity and resolution.