Design, Analysis and Implementation of Integrated Micro-Thermal Control Systems

While there has been a growing emergence of circuit designs for the life sciences, there is an important issue that remains largely unaddressed. Although advanced design techniques have been applied to circuits capable of measuring very small amplitude, high signal to noise ratio signals, with many custom circuit designs for these applications (Harrison and Charles, 2003), there remains a proverbial elephant in the room. The systems used to measure these signals provide no means of accurate thermal control. This is especially surprising considering the huge dependance in the behavior of both biological and electrical systems upon temperature. In fact, the vast majority of electrical cellular assays are performed on dying cells! We present a systematic method of incorporating a high-accuracy, closed-loop thermal feedback system into hybrid systems for the life sciences. We introduce a thermal stabilization chip containing a heater and PTAT temperature sensor including the heater control circuit. We then provide a description of the PID control loop. This is followed by both computational data via finite element analysis and empirical data that assesses the thermal performance of the chip. Finally, we demonstrate the advantages of the system with comparative results of cell culture.