The objective of this research is to develop a micro-device that is capable of picowatt-resolution, room temperature calorimetric measurements. Such technology could enable new understanding of systems-level biological properties of single biological cells. The work involves micro- and nanofabrication, micro-scale heat transfer, and ultra-sensitive instrumentation components.
Intellectual Merit: Although the long-term objective is to apply picowatt calorimetry to measure energy transduction in biological cells, this research will focus on the design, fabrication and demonstration of a micro-device capable of measuring steady (DC) power outputs with picowatt resolution. This level of resolution represents an improvement of approximately three orders of magnitude compared to the most precise room temperature calorimetric devices available today. To achieve such precise power resolution a device consisting of a micro-island suspended by thin and long beams will be used as this approach enables thermal isolation of the test section. Additional features include the incorporation of a high-sensitivity bimaterial cantilever for optically sensing temperature changes in the suspended region of the device and a microfluidic channel that enables the modulation of the thermal conductance of the micro-device.
Broader Impact and Significance: This research will lay a foundation for studying the mechanisms that maintain and control biological cells. More broadly, picowatt calorimetry will provide new insight into biology, materials science and electrochemistry. The project involves education and training of K-12 and undergraduate students, including students from underrepresented groups, by providing a variety of educational and research experiences.
The goal of this project was to develop the calorimetric tools required to measure heat outputs with picowatt resolutions. Towards this goal, in this project, we have developed an experimental platform involving custom-fabricated microdevices that enables us to measure modulated heat currents with picowatt resolution (Sadat et al., Appl. Phys. Lett., 2011). To elaborate, we developed a microfabricated device capable of <4 pW resolution—an order of magnitude improvement over state-of-the-art room temperature calorimeters. This was achieved by the incorporation of two important features. First, the active area of the device was thermally isolated by thin and long beams with a total thermal conductance (G) of ~600 nW/K. Further, a bimaterial cantilever thermometer capable of a temperature resolution (?Tres) of ~4 µK was integrated into the microdevice. The small thermal conductance and excellent temperature resolution enable measurement of heat currents with a resolution <4 pW. Further, to enable the measurement of unmodulated heat currents with picowatt resolution we have developed a novel nanopositioning platform that will enable us to modulate the thermal conductance of microscale devices without physically making contact to the devices. These results are described in our recent manuscript (Ganjeh et al., Rev. Sci. Instrum., 2012). We anticipate that by successfully combining these two advances it will be possible to probe heat outputs from single biological cells and organelles with picowatt resolution
