With accelerating trends in miniaturization of semiconductor devices, techniques for energy harvesting become increasingly important, especially in wearable technologies and sensors for the internet of things. Although thermoelectric systems have many attractive attributes in this context, maintaining large temperature differences across the device terminals and achieving low-thermal impedance interfaces to the surrounding environment become increasingly difficult to achieve as the characteristic dimensions decrease. Here, we propose and demonstrate an architectural solution to this problem, where thin-film active materials integrate into compliant, open threedimensional (3D) forms. This approach not only enables efficient thermal impedancematching but alsomultiplies the heat flow through the harvester, thereby increasing the efficiencies for power conversion. Interconnected arrays of 3D thermoelectric coils built using microscale ribbons of monocrystalline silicon as the active material demonstrate these concepts. Quantitative measurements and simulations establish the basic operating principles and the key design features. The results suggest a scalable strategy for deploying hard thermoelectric thin-film materials in harvesters that can integrate effectively with soft materials systems, including those of the human body.
Bibliographical noteFunding Information:
We acknowledge the support from the U.S. Department of Energy, Office of Science, Basic Energy Sciences through the following programs: J.A.R. acknowledges DE-FG02-07ER46471; G.J.S. acknowledges S3TEC, an Energy Frontier Research Center (DE-SC0001299). Y.H. acknowledges the support from the NSF (1400169, 1534120, and 1635443). Z.X. acknowledges the support from the National Natural Science Foundation of China (11402134). K.J.Y. acknowledges the support from the National Research Foundation of Korea (NRF- 2017M1A2A2048880 and NRF-2018M3A7B4071109) and the Yonsei University Future-leading Research Initiative (RMS2 2018-22-0028). The experimental work was carried out, in part, in the Frederick Seitz Materials Research Laboratory, Central Research Facilities, University of Illinois.
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