Mechanical Engineering Thermal

Xiangwen Chen

**** *. ********** ****, ** ***-** Email: *********@*****.***

Pasadena, CA 91125 Cell phone: 626-***-****

Summary

My expertise covers thermal experimentations and simulations (10+ years of experience), optical pump-probe spectroscopy (5+ years), clean room fabrications (5+ years), materials characterizations (5+ years) and programming (9+ years).

I led and participated 10+ research projects in which I built up my knowledge, versatile skillset and team spirit, and developed detail-oriented and hard-working style. I am seeking opportunities in thermal management of electronics, fabrications, or optical applications. Current appointment

2012 – Postdoctoral scholar at California Institute of Technology (Caltech) Pasadena, California USA Education

2011 Ph.D. in Mechanical Engineering, Iowa State University (ISU) Ames, Iowa USA 2008 M.S. in Engineering Thermophysics, Zhejiang University (ZJU) Hangzhou, China 2006 B.S. in Thermal Energy & Power Engineering, Zhejiang University (ZJU) Hangzhou, China Skills

Experimental utilities: thermal test, cryogenic system, vacuum system, temperature controlling equipment, electronic test equipment, machining, pressured gases Optical: optical component and system design, ultra-fast lasers (including cavity alignment), Raman spectroscopy

Fabrication: e-beam lithography, photolithography, wet etching, plasma dry etching; thin film deposition by e-beam evaporation, magnetron sputtering and pulsed laser deposition Characterization: Atomic force microscope (AFM), profilometry, ellipsometry, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), focused ion beam (FIB), X-ray diffraction

(XRD), transmission electron microscope (TEM)

Simulation tool: ANSYS Fluent, ANSYS HFSS, COMSOL multiphysics Engineering tool: AutoCAD, Labview

Programming language: Matlab, Fortran, Python, C

Professional experience

Postdoc at Caltech (Advisor: Austin Minnich) 2012 – present Thermal transport characterization at the micro/nanoscale with optical techniques and micro/nanofabrications: Built 3 laser-based pump-probe spectroscopies for thermal conductivity measurements: time-domain thermoreflectance with ultra-fast laser, broadband frequency-domain thermoreflectance with heterodyning detection, asynchronous optical sampling system which synchronizes two femtosecond lasers. Fabricated nanoscale line array heaters by lithography, and experimentally investigated the thermal conductivity correspondingly with ultra-fast pump-probe method. The results show significance in two aspects:

Establishing the spatial frequency of the heating profile as the critical parameter that governs heat transport at nanoscale for the first time, providing a foundational understanding of how materials dissipate heat at Resume - Xiangwen Chen “Green card” holder Page 1

small lengths.

High thermal resistance of heat flow at small scale can be highly improved by rationally engineering the spatial arrangement of heat sources, even if the individual heaters are of nanoscale dimensions. Designed and fabricated different interfaces between aluminum thin film and Si substrate, and measured the dynamics of thermal transport in the 2-layer system, by combining my colleague’s ab-initio phonon transport modeling, the thermal phonon transmission coefficients at solid interfaces were extracted. Collaborated with colleague to demonstrate a generalized Fourier’s law at nondiffusive regime by time-domain thermoreflectance measurements on MgO with nanoscale heating patterns, providing a constitutive relations for heat transport at nondiffusive regime. Conducted the first quantitative measurements of the c-axis mean free paths of thermal phonons in graphite at different temperatures, through thermal conductivity measurements on graphite flakes of variable thickness with time-domain thermoreflectance method.

Experimentally investigated the thermal conductivity of thin films, including high entropy alloys, SiN, thermoelectrics (BiTe, SbTc, Cu2Se), and superlattices (SiGe, AlGaN). Characterized thermal properties of thermoelectric layer and isolation layer in thermopile detectors for thermal probing in universe. The thermal analysis provided essential information for materials selection and structural design.

Designed a circuit to power wireless sensors with thermoelectric on aircraft by harvesting waste heat. The locally powered configurations will reduce the wires and increase the reliability. Designed a circuit of balancing detection to reduce the baseband noise and improve detection sensitivity in thermal signal measurement.

Graduate Research/Teaching Assistant at ISU (Advisor: Xinwei Wang) 2008 – 2011 Laser-based thermophysical properties measurements and nanostructure diagnostics: Characterized thermal conductivity of thin films by using photothermal technique, including P3HT, TiO2, diamond and SiC, hydrogen storage material vanadium-doped magnesium porous nanostructures before and after H2 absorption.

Thermal transport investigations in atomic force microscope (AFM) tip-substrate system with experiments and simulations:

Simulated thermal transport of Si AFM tip under laser irradiation by using ANSYS Fluent and high frequency structure simulator (HFSS).

Measured temperature response of Si AFM tip under laser irradiation with Raman thermometry method, achieving spatial resolution of 1 μm.

Worked on temperature measurements in Si substrate under nanotip focused laser at a sub-10 nm region with Raman thermometry method.

Designed a scanning photothermal microscopy system, consisting of customized atomic force microscopy, lock-in amplifier, and laser, to diagnose the sub-surface defects such as interfaces, voids, impurities, etc. at nanoscale resolution.

Assisted in teaching course “Heat Transfer”.

Master student in the State Key Lab of Clean Energy Utilization at ZJU 2006 – 2008 Combustion-generated pollutants control in coal-fired power plants: Designed a limestone-gypsum Flue Gas Desulfurization scrubber with sieve tray. Through experiments and flow simulations by FLUENT, the optimization of the structure of sieve tray (opening, diameter of the holes, install position) and working conditions (flue gas velocity, liquid-gas ratio) were acquired for simultaneous removal of SO2 and NOx.

Resume - Xiangwen Chen “Green card” holder Page 2

Built a bubble Flue Gas Desulfurization tower for multi-pollutant (SO2, NOx, and Hg0+) removal using limestone as absorber and Na2O2 as additive, and tested the efficiency of pollutants removal under different working conditions.

Experimentally investigated the absorbing capability of slaked CaO for SO2 and NOx, and Hg0+ in calcium- based semi-dry technique. The optimal slaking conditions were systematically explored. Publications and Presentations

11 Journal publications (plus 1 submitted, 2 in preparation), 2 invited talks, 14 conferences presentations with 6 oral ones. Below are a few highlights:

X. Chen, C. Hua, H. Zhang, N.K. Ravichandran, and A.J. Minnich, Quasiballistic thermal transport from nanoscale heaters and the role of the spatial frequency. Submitted, 2017. ( contribute equally). C. Hua, X. Chen, N.K. Ravichandran, and A.J. Minnich, Experimental metrology to obtain thermal phonon transmission coefficients at solid interfaces. Physical Review B 95:205423, 2017. ( contribute equally), chosen as Editor’s suggestion.

H. Zhang, X. Chen, Y.D. Jho, and A.J. Minnich, Temperature-dependent mean free path spectra of thermal phonons along the c-axis of graphite. Nano Letters 16(3):1643, 2016. ( contribute equally). Invited talk at Jet Propulsion Laboratory, “Thermal transport under the microscope: Uncovering the key parameters that govern thermal transport.” Pasadena, CA; June 30, 2017. Leadership and Service

Mentor 10 students/scholars to be professionals in thermal sciences and engineering. Session Chair, ASME International Mechanical Engineering Congress & Exposition, 2013 – 2015. Reviewer for 20+ prestigious journals and conferences, including Advanced Materials, Nano Energy, Journal of Heat Transfer, etc.

Tennis club organizer for Chinese student and scholar community at ISU, 2009 – 2011. Main Courses

Advanced Heat and Mass Transfer, Solar Energy Systems, Advanced Thermodynamics, Micro/Nano Manufacturing, Statistical Mechanics, SEM, Modern Optics, Nanoelectronics. References

Austin J. Minnich, Professor of Mechanical Engineering and Applied Physics California Institute of Technology

1200 E. California Blvd, MC 104-44, Pasadena, CA 91125 Email: *****.*******@*******.***, Phone: 626-***-**** Xinwei Wang, Professor of Mechanical Engineering

Iowa State University

2010 Black Engineering, Ames, IA 50011

Email: ******@*******.***, Phone: 515-***-****, Fax: 515-***-**** Jonathan A. Malen, Associate Professor of Mechanical Engineering Carnegie Mellon University

5000 Forbes Avenue, Scaife Hall 413, Pittsburgh, PA 15213 Email: ********@******.***.***, Phone: 412-***-****, Fax: 412-***-**** Resume - Xiangwen Chen “Green card” holder Page 3

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