MEMS-based microcalorimeter for liquid samples
American Society of Mechanical Engineers, Micro-Electromechanical Systems Division Publication (MEMS)
Advances in MEMS technology has enabled the development of microcalorimeters that have significant improvement in resolution over conventional calorimeters and require smaller samples. However, microcalorimeters have yet to accomplish the variety of tasks that are done by conventional calorimeters, such as study of the thermal properties of polymers and proteins that are typically in liquious state. These applications are especially important in the biomedical field, where combinatorial approaches are used to test a large number of variations in biomaterials. We present a design for a MEMS microcalorimeter that can be applied for a variety of liquid samples. The basic design of the microcalorimeter consists of low stress silicon nitride thin film with nickel resistive heater and thermometer. The heater and thermometer are thermally isolated from each other so that the thermometer accurately measures the temperature of the sample. The silicon nitride film containing the device is suspended over silicon substrate to achieve thermal isolation. Modulation calorimetry technique is used to determine the specific heat of the sample based on the temperature response of the sample when subjected to an AC-modulated heat source. A numerical model was developed to model the thermal behavior of the device. Initial numerical studies found that the device operates optimally at low frequencies, where with appropriate corrections, the device can yield values of heat capacity that are within one percent of the actual value.
Tada, H., & Wong, P. (2003). MEMS-based microcalorimeter for liquid samples. American Society of Mechanical Engineers, Micro-Electromechanical Systems Division Publication (MEMS), 5, 577-581. https://doi.org/10.1115/imece2003-41150