Thermal management of BioMEMS

Integrated microfluidic devices for amplification and detection of biological samples that employ closed-loop temperature monitoring and control have been demonstrated within a multilayer low temperature co-fired ceramics (LTCC) platform. Devices designed within this platform demonstrate a high level of integration including integrated microfluidic channels, thick-film screen-printed Ag-Pd heaters, surface mounted temperature sensors, and air-gaps for thermal isolation. In addition, thermal-fluidic finite element models have been developed using CFDRC ACE+ software which allow for optimization of such parameters as heater input power, fluid flow rate, sensor placement, and air-gap size and placement. Two examples of devices that make use of these concepts are provided. The first is a continuous flow polymerase chain reaction (PCR) device that requires three thermally isolated zones of 94°C, 65°C, and 72°C, and the second is an electronic DNA detection chip which requires hybridization at 35°C. Both devices contain integrated heaters and surface mount silicon transistors which function as temperature sensors. Closed loop feedback control is provided by an external PI controller that monitors the temperature dependent I-V relationship of the sensor and adjusts heater power accordingly. Experimental data confirms that better than +/- 0.5°C can be maintained for these devices irrespective of changing ambient conditions. In addition, excellent matching with model predictions has been achieved, thus providing a powerful design tool for thermal-fluidic microsystems.