College of Engineering Mechanical Engineering Birck Nanotechnology Center Energy Center
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About the PI:

Professor Ruan received his B.S. and M.S. in Engineering Thermophysics from Tsinghua University in 2000 and 2002, respectively. He received an M.S. in Electrical Engineering and Ph.D. in Mechanical Engineering from the University of Michigan at Ann Arbor, in 2006 and 2007 respectively. He then joined Purdue as an assistant professor. He was promoted to associate professor with tenure in 2013 and to full professor in 2017. Dr. Ruan received several awards, including the NSF CAREER Award in 2012, the ASME Heat Transfer Division Best Paper Award in 2015, the College of Engineering Early Career Research Excellence Award in 2016, the School of Mechanical Engineering Outstanding Graduate Student Mentor Award in 2016, the B.F.S. Schaefer Award in 2017, and was named a University Faculty Scholar in 2017. He was an Air Force Summer Faculty Fellow at the Wright Patterson Air Force Base at Dayton, Ohio in 2010, 2011, and 2013. He currently serves as an Editorial Board Member for Scientific Reports, a journal published by the Nature Publishing Group, and as an associate editor for ASME Journal of Electronic Packaging. [CV]


Office: ME 2153 and BNC 1270     Phone: 765-494-5721 (ME), 765-494-6603 (BNC), Fax: 765-494-0539    

e-mail: ruan@purdue.edu

[see people in the group]



Positions open: We may have positions for postdoc fellows, graduate students, and undergraduate students. Please check here.


12/2017: News release: Our work of four-phonon scattering has been covered by Purdue News Services and numerous other scientific media with the title: "Researchers solve ‘four-phonon’ thermal-conductivity obstacle key to tech applications”:

10/2017: Student award. Xiangyu received the third-place Best Poster Award at the 2017 CTRC Fall Meeting. Congratulations to Xiangyu!


10/2017: Invited Seminar. Dr. Ruan gave an invited seminar at the University of California at Santa Barbara.


08/2017: Student award. Joseph Peoples joined our group as a Ph.D. student and receives the Winkelman Fellowship from the School of Mechanical Engineering. Congratulations, Joe!


[more news ...]

Mission Statement:


Sustainable energy and energy efficiency are among the greatest challenges facing the society, and heat transfer scientists and engineers can contribute. Solutions to these challenges rely on extraordinarily fundamental and innovative approaches. In our lab, we are developing efficient energy and renewable energy technologies using the emerging nanotechnology.


The behavior of all energy systems can be related to atomic-scale description. With an atomic-level knowledge of the thermal energy carriers (photon, electron, phonon, and fluid particle), one is able to design nano- and micro-structures with the desired size effects, or to synthesize new materials with the desired functionalities. Our lab is building and expanding the understanding of the fundamentals of atomic-level carrier transport and interactions, and is applying this knowledge to important applications for energy efficiency and electronics thermal management technologies.


Current projects fall in two main themes: nanoscale heat conduction, and nano-photonics (including nanoscale thermal radiation). Projects in the nanoscale heat conduction (or nano-phononics) category include: (1) high-performance nanostructured thermoelectric materials for power generation and thermoelectric refrigeration; (2) thermal transport and thermal rectification in carbon nanotube and graphene for electronic thermal management applications; (3) thermal interface resistance across CNT (or graphene)-metal interfaces for electronic thermal management applications. Projects in the nano-photonics category include: (4) Suppression of electron-phonon coupling in quantum dot solar cell materials for enhanced efficiency; (5) Enhanced optical absorption in silicon nanowire arrays for potentially enhanced solar cell efficiency; (6) Multiscale control of thermal radiation in ordered array of carbon nanotubes; (7) enhanced laser cooling of semiconductors and ion-doped solids.


These projects involve theoretical, computational, and experimental components. Currently our lab devotes 2/3 efforts to theoretical and simulation studies, and 1/3 effort to experimental work. Theoretical tools include heat transfer, materials science, quantum mechanics, solid state physics, optics, and electromagnetic theory. Computational tools involve multiscale simulation techniques of nanoscale energy transport, including molecular dynamics simulations, first principles calculations, Monte-Carlo simulations, and Boltzmann transport theory. Experiments include fabrication of nanomaterials and devices, and characterizations of these materials and devices using advanced imaging and spectroscopy techniques. Detailed information of our research can be found here.


We have labs in both the ME building and the Birck Nanotechnology Center. We are also associated with the Energy Center at Purdue.

Most Recent Publications:


[91] B. Xu, T.L. Feng, M.T. Agne, Q. Tan, Z. Li, K. Imasato, L. Zhou, J.H. Bahk, X.L. Ruan, G.J. Snyder, and Y. Wu, "Manipulating Band Structure through Reconstruction of Binary Metal Sulfide towards High-Performance, Eco-Friendly and Cost-Efficient Thermoelectrics in Nanostructured Bi13S18I2," Angew. Chem. Int. Ed., accepted (2018).


[90] T.L. Feng and X.L. Ruan, "Four-phonon scattering reduces intrinsic thermal conductivity of graphene and the contributions from flexural phonons," Phys. Rev. B 97, 045202 (2018). [PDF]


[89] S.V. Bhat, M. Dhanasekar, K.M. Rickey, and X.L. Ruan, "Facile In Situ Growth of Nanostructured Copper Sulfide Films Directly on FTO Coated Glass Substrate as Efficient Counter Electrodes for Quantum DOt Sensitized Solar Cells," Chemistry Select 2, 10736-10740 (2017). [PDF]


[88] X.W. Wu, J. Walter, T.L. Feng, J. Zhu, H. Zheng, J.F. Mitchell, N. Biškup, M. Varela, X.L. Ruan, C. Leighton, and X.J. Wang,Glass-like Through-Plane Thermal Conductivity Induced by Oxygen Vacancies in Nanoscale Epitaxial La0.5Sr0.5CoO3-δ," Adv. Funct. Mater. 1704233 (2017). [PDF]


[87] T.L. Feng, L. Lindsay, and X.L. Ruan, “Four phonon scattering significantly reduces thermal conductivity is solids,” Phys. Rev. B Rapid Communications, 96, 161201(R) (2017). [PDF]


[86] X.L. Li, W. Park, Y.P. Chen, and X.L. Ruan, “Absence of coupled thermal interfaces in Al2O3/Ni/Al2O3 sandwich structure,” Appl. Phys. Lett. 111, 143102 (2017). [PDF]


[complete list of publications]

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