Integrated circuit thermopile as a new type of temperature modulated calorimeter

Abstract

Thermopiles, integrated into a thin silicon membrane, are used in some calorimetric applications (e.g. Setaram SETline120 portable thermal analyzer) that utilize temperature ramps of the thermostat to obtain the caloric response. A new calorimetric method is proposed, which uses an integrated circuit thermopile (ICT) in an oscillating mode. A heater integrated into the membrane drives temperature oscillations and the thermopile senses the temperature gradient across the membrane. ac calorimetry and the 3-omega method do not measure total heat losses and have an inherent quasi-adiabatic low frequency limit. On the other hand, the thermopile setup can measure total heat losses that permits one to monitor enthalpy changes in a sample, e.g. during crystallization. Low frequency measurements are limited only by sensor sensitivity. Preliminary results show that the same experimental setup can be used to make dynamic heat capacity measurements over a frequency range from 1 mHz to 100 Hz. At high frequencies (1 Hz and higher), heat capacity of nanogram samples can be measured.