A MEMS Nanocalorimeter for Biomolecular Characterization

This paper presents an integrated MEMS nanocalorimeter with nanowatt thermal power sensitivity and on-chip control of calorimetric chamber temperatures for measuring structural transitions of biomolecules in solution. The device features two identical polymeric freestanding membranes, resistive temperature sensors and heaters, and a low-noise thermopile differential temperature sensor between the two membranes. With the integrated resistive heaters and temperature sensors, on-chip feedback temperature control is achieved to allow varying temperatures with prescribed rates. During measurements, the temperatures of the liquid sample and reference materials are scanned over a continuous range with on-chip temperature control, and the differential thermal response is monitored by the thermopile. By using low-noise thermopile temperature sensor and optimized thermal structures, we obtain sensitivity at about 50 nanowatt. Integrated with PDMS microfluidic channels and chambers, the calorimeter allows efficient handling and measurements of small volumes (~ mul) of liquid samples. We have used the device to measure protein denaturation at low concentrations