Calorimetry is used extensively for the characterization of molecular binding and for the study of the internal structure of biomolecules in life science research. There is increasing interested in the use of calorimetry to measure the energetics of cell and developmental biological processes, but these applications have been hampered by the insufficient sensitivity of instruments to allow measurements at the single-cell scale.<br/><br/>We have developed a calorimetry sensor that has a sensitivity in the picowatt range, that can make measurements on biological samples as small as a 1 µL, and that has a response time on the order of seconds. The sensor consists of low-noise thermopiles on a thin silicon nitride membrane that allow direct differential temperature measurements between a sample and four coplanar references. Using a design with four references makes it possible to eliminate the effects of any in-plane temperature gradients that may arise during the measurement as a result of small changes in the ambient temperature. The resulting sensor has a resolution on the order of 28 picowatt, which is a near order-of-magnitude increase in sensitivity above current state-of-the-art calorimeters. An ultralow long-term (8-h) temperature drift (0.18 µK) of the calorimeter is enabled by a small custom-built chamber with control over the interior temperature and humidity.<br/><br/>We demonstrate the capability of the sensor by measuring the heat dissipated during an enzymatically catalyzed biochemical reaction in a microliter-sized liquid droplet of active matter. The extraordinary sensitivity combined with the special handling of aqueous samples makes the sensor ideally suited for the direct measurement of metabolic rates and for the study of non-equilibrium processes in a range of materials systems.

Picowatt single-cell calorimetry for application to chemical reactions and biochemistry

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.