Woodruff School of Mechanical Engineering
Mechanical Engineering Seminar
Thermal Conduction and Radiation Properties of Metamaterials and Novel Thermal Management Designs
Prof. Jaeho Lee
University of California, Irvine, Mechanical & Aerospace Engineering
Tuesday, October 15, 2019 at 11:00:00 AM
MRDC Building, Room 4211
The seminar talk will first introduce and share recent findings of thermal conduction phenomena in silicon nanostructures, which are relevant for advanced electronic systems. When material dimensions become comparable to or smaller than the average distance travelled by heat carriers in bulk, the material,s thermal conductivity begins to deviate from the bulk property. The thermal conductivity reduction in silicon nanostructures can be considered either detrimental for heat dissipation in electronic systems or as an opportunity for thermoelectric energy conversion. Our work has focused on identifying the fundamental mechanisms of thermal transport in holey silicon nanostructures and the contributions of phonon coherence and backscattering through combined experimental and computational approaches. Our recent study also shows that silicon nanostructures with a controlled pore design can lead to a low thermal conductivity in the in-plane direction and a high thermal conductivity in the cross-plane direction, and that the anisotropy is ideal for thermoelectric cooling. While the low in-plane thermal conductivity sustains a lateral temperature gradient from hot to cold Peltier junctions, and the high cross-plane thermal conductivity dissipates heat vertically from a hot spot to an on-chip cooling structure, which can address local heat fluxes of 1 kW/cm2 and beyond for high-power electronics. Our work further shows possibilities of manipulating heat flow using holey silicon nanostructures and potential designs of CMOS-compatible thermal metamaterials, which enable heat guiding and even cloaking and will lead to breakthroughs in thermal management of electronics packaging. The second part of the talk will present recent findings of thermal radiation by optical metamaterials and their use for thermal management in the ambient environment. While the sun heats up a surface in the visible to near-infrared wavelengths, the surface radiates heat to the atmosphere and to the cold space in mid-infrared wavelengths. The concept of radiative cooling has received much attention because we can passively control the surface temperature. Our work focuses on engineering the surface emissivity spectrum not only selectively but also dynamically so that we can enable dynamic thermal control. We integrate a surface material with a stretchable polymer and use strain-induced morphology variations to control optical and thermal properties. Our selective emitters based on reconfigurable 2D materials and thin films provide significant control over surface temperature and a cooling flux up to 100 W/m2 in the ambient environment, which can lead to advanced thermal management of wearables and energy-efficient buildings.
Jaeho Lee is an assistant professor of Mechanical and Aerospace Engineering and the Henry Samueli Career Development Chair at the University of California, Irvine. He received a B.S. in Mechanical Engineering from Georgia Institute of Technology in 2007 with highest honors, an M.S. and a Ph.D. in Mechanical Engineering with a minor in Electrical Engineering at Stanford University in 2012. His Ph.D. thesis work was on electro-thermal phenomena in phase change memory devices under the guidance of Professor Kenneth Goodson. Prior to joining UC Irvine in 2015, he worked as a postdoctoral scholar with Peidong Yang in Materials Sciences Division at Lawrence Berkeley National Laboratory. He worked as a summer faculty fellow with the Thermal Energy Conversion Research and Advancement Group at the Jet Propulsion Laboratory in 2016. He was selected as a recipient of the Hellman Faculty Fellow in 2018. His research focuses on controlling thermal conduction and radiation by metamaterials and developing solid-state thermal management solutions for electronics and aerospace systems.
Lunch will be provided.
Meet the speaker