Positions open: We may
have positions for postdoc
fellows, graduate students, and undergraduate students. Please check here.
04/2015: M.S. thesis
defense. Chris Robinson has successfully defended his MS
thesis. Congratulations, Chris!
04/2015: Invited Talk.
Dr. Ruan gave an invited talk at the 2015 MRS Spring
03/2015: Student Award.
Yan Wang received the College of Engineering Outstanding
Graduate Student Research Award. Congratulations, Yan!
03/2015: M.S. thesis
defense. Eshaan Mathew has successfully defended his MS
thesis. Congratulations, Eshaan!
Seminars. Dr. Ruan was invited to
visit Taiwan and give seminars at National Cheng Kung
University, National Taiwan University, and National Tsing
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
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
Current projects fall in two
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
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
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
We have labs in both the
ME building and the
Birck Nanotechnology Center. We are also associated with
Energy Center at Purdue.
Most Recent Publications:
 B. Qiu, Z.T. Tian, A.
Vallabhaneni, B.L. Liao, J.M. Mendoza, O.D. Restrepo, X.L.
Ruan, and G. Chen, “First-principles simulation of electron
mean-free-path spectra and thermoelectric properties in
silicon”, EPL 109, 57006, (2015). [PDF]
 Y. Wang, C.J. Gu, and X.L.
Ruan, “Optimization of the random multilayer structure to
break the random-alloy limit of thermal conductivity”,
Appl. Phys. Lett. 106, 073104 (2015). [PDF]
 Z.Y. Wang, T.L. Feng, and
X.L. Ruan, “Thermal conductivity and spectral phonon
properties of freestanding and supported silicone”, J.
Appl. Phys. 117, 084317 (2015). [PDF]
 H. Bao, A. Kumar, Y. Cai,
Y. Ji, T.S. Fisher, and X.L. Ruan, Optical Properties of
Thin Graphitic Nanopetal Arrays, Journal of Quantitative
Spectroscopy and Radiative Transfer 158, 84–90
 Y. Wang, H.X. Huang, and
X.L. Ruan, "Decomposition of coherent and incoherent phonon
conduction in superlattices and random multilayers,"
Phys. Rev. B 90, 165406 (2014). [PDF]
 B.T. Spann, S.V. Bhat,
Q. Nian, K.M. Rickey, G.J. Cheng, X.L. Ruan, and X.F. Xu,
“Enhancing Photo-induced Ultrafast Charge Transfer across
Heterojunctions of CdS and Laser-Sintered TiO2 Nanocrystals,”
Phys. Chem. Chem. Phys.
list of publications]