Open AccessA Micromachined Picocalorimeter Sensor for Liquid Samples with Application to Chemical Reactions and Biochemistry
Author(s) -
Bae Jinhye,
Zheng Juanjuan,
Zhang Haitao,
Foster Peter J.,
Needleman Daniel J.,
Vlassak Joost J.
Publication year - 2021
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.202003415
Subject(s) - thermopile , microscale chemistry , calorimetry , silicon nitride , calorimeter (particle physics) , chemistry , analytical chemistry (journal) , surface micromachining , noise equivalent power , materials science , nanotechnology , optoelectronics , chromatography , silicon , optics , fabrication , infrared , thermodynamics , physics , mathematics education , mathematics , responsivity , detector , photodetector , medicine , alternative medicine , pathology
Calorimetry has long been used to probe the physical state of a system by measuring the heat exchanged with the environment as a result of chemical reactions or phase transitions. Application of calorimetry to microscale biological samples, however, is hampered by insufficient sensitivity and the difficulty of handling liquid samples at this scale. Here, a micromachined calorimeter sensor that is capable of resolving picowatt levels of power is described. 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, which significantly reduces thermal drift. The partial pressure of water in the ambient around the sample is maintained at saturation level using a small hydrogel‐lined enclosure. The materials used in the sensor and its geometry are optimized to minimize the noise equivalent power generated by the sensor in response to the temperature field that develops around a typical sample. The experimental response of the sensor is characterized as a function of thermopile dimensions and sample volume, and its capability is demonstrated by measuring the heat dissipated during an enzymatically catalyzed biochemical reaction in a microliter‐sized liquid droplet. The sensor offers particular promise for quantitative measurements on biological systems.