In this talk, I will give three examples about utilizing specially engineered nanostructured materials to develop advanced thermal components. First, I will demonstrate a "super-solder" consisting of a heterogeneous copper-tin nanowire array that has polymer-like compliance with a shear modulus 2-3 orders of magnitude lower than traditional solders and can reduce thermal resistance by two times as compared with the state-of-the-art thermal interface materials. The super-solder also exhibits exceptional long-term reliability with >1,280 thermal cycles over a wide temperature range. Second, I will report an ultra-high-contrast and reversible nanoscale thermal switch based on the structural phase transition in crystalline polyethylene nanofibers, which enables a ~ 10X thermal switching ratio between the on-state (high) and the off-state (low) thermal conductance values. To the best of our knowledge, the observed high switching ratio exceeds by far any reported experimental values for solid-solid phase transition, solid-liquid phase transition and desiccation-hydration of materials. By fabricating a heterogeneous “irradiated-crystalline nanofiber junction” using an electron beam, we also demonstrated a high-performance solid-state nanoscale thermal diode with a rectification factor as high as ~ 54 %, which exceeds any existing solid-state nanoscale thermal diodes. Finally, I will present a general theoretical framework for designing prefect thermal infrared emitters at the nanoscale, which can have a superior emission power several orders of magnitude larger than blackbody radiation compared to their surface areas. By using these nanoscale thermal emitters as fundamental building blocks, we experimentally demonstrate a new type of macroscopic perfect and tunable thermal emitters. The novel perfect thermal emitters have important practical impacts in a variety of technologies, e.g., heat assisted magnetic recording, radiative cooling, thermal infrared imaging, and thermophotovoltaic energy conversion.
Sheng Shen is a Professor at the Mechanical Engineering Department of Carnegie Mellon University (CMU). He also holds courtesy appointments in both the Electrical and Computer Engineering and the Materials Science and Engineering Departments at CMU. He received his PhD degree from the Mechanical Engineering Department, MIT, in 2010. Prior to joining CMU in 2011, he conducted his postdoctoral research at UC-Berkeley. His research interests include nanoscale heat transfer and energy conversion, nanophotonics, and their applications in energy conversion, thermal management, sensing, and multifunctional materials. Professor Shen is a recipient of NSF CAREER Award, DARPA Director's Fellowship, DARPA Young Faculty Award, and Elsevier/JQSRT Raymond Viskanta Award for Spectroscopy and Radiative Transfer. He also received the CMU Dean's Early Career Fellowship, the Philomathia Foundation Research Fellowship in Alternative Energy Research from UC-Berkeley, a Hewlett-Packard Best Paper Award from ASME Heat Transfer Division, and a Best Paper Award in Julius Springer Forum on Applied Physics.
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