Baratunde A. Cola
Associate Professor, Mechanical Engineering Georgia Tech College of Engineering
Georgia Tech College of Engineering
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Media
Social
Biography
Areas of Expertise
Selected Accomplishments
National Academy of Sciences US Kavli Frontiers of Science Fellow
2014
ASME Bergles-Rohsenow Young Investigator Award in Heat Transfer
2015
Atlanta Business Chronicle’s 40 under 40
2015
Education
Purdue University
Ph.D.
Heat Transfer and Nanomaterials
2008
Activities and Societies: Vice President of Nanotechnology Student Advisor Council
Intel Fellow, NASA Institute of Nanoelectronics and Computing Fellow, Purdue Fellow
Vanderbilt University
M.S.
Mechanical Engineering
2004
Activities and Societies: Started engineering software company after taking New Ventures Course in Owen School of Management.
Vanderbilt University
B.E.
Mechanical Engineering
2002
Activities and Societies: Fullback on Football Team
Links
Selected Media Appearances
Advanced Metal Patterning Makes Electricity from Light
IDTechEx.com online
2019-07-29
In the world of flexible electronics, printed electronics and In Mold Structural Electronics IMSE ™ the staple is metal patterning for basic purposes such as interconnects. Those making conductive inks such as DuPont, and conductive micropatterning such as Nissha are often regarded as at the foothills of that world, the clever stuff involving semiconductor layers, optoelectronics, OLEDs and so on.
Researchers Boost Efficiency and Stability of Optical Rectennas
Georgia Tech News Center online
2018-01-26
The research team that announced the first optical rectenna in 2015 is now reporting a two-fold efficiency improvement in the devices — and a switch to air-stable diode materials. The improvements could allow the rectennas – which convert electromagnetic fields at optical frequencies directly to electrical current – to operate low-power devices such as temperature sensors.
Two early career researchers honored with Alan T. Waterman Award
National Science Foundation online
2017-04-13
The National Science Foundation (NSF) today recognized Baratunde "Bara" A. Cola of the Georgia Institute of Technology and John V. Pardon of Princeton University with the nation's highest honor for early career scientists and engineers, the Alan T. Waterman Award. This marks only the second time in the award's 42-year history that NSF selected two recipients in the same year.
Engineered “Sand” May Help Cool Electronic Devices
Research Horizons online
2016-07-13
Baratunde Cola would like to put sand into your computer. Not beach sand, but silicon dioxide nanoparticles coated with a high dielectric constant polymer to inexpensively provide improved cooling for increasingly power-hungry electronic devices.
Carbice Nanotechnologies seeks to scale heat dissipation and management technology
Georgia Tech News Center online
2016-05-02
The demand for ever-powerful and faster electronic devices has led to the development of innovative smartphones, tablets, computers, and other products.
Patents
Methods for attaching carbon nanotubes to a carbon substrate
US8919428B2
2014-12-30
Vertically oriented carbon nanotubes (CNT) arrays have been simultaneously synthesized at relatively low growth temperatures (i.e.,
Electrothermal interface material enhancer
CA2666815C
2013
Vertically oriented carbon nanotubes (CNT) arrays have been simultaneously synthesized at relatively low growth temperatures (i.e., < 700°C) on both sides of aluminum foil via plasma enhanced chemical vapor deposition. The resulting CNT arrays were highly dense, and the average CNT diameter in the arrays was approximately 10 nm, A CNT TIM that consist of CNT arrays directly and simultaneously synthesized on both sides of aluminum foil has been fabricated. The TIM is insertable and allows temperature sensitive and/or rough substrates to be interfaced by highly conductive and conformable CNT arrays. The use of metallic foil is economical and may prove favorable in manufacturing due to its wide use.
Palladium thiolate bonding of carbon nanotubes
US8541058B2
2013
Carbon nanotube (CNT) arrays are attractive thermal interface materials with high compliance and conductance that can remain effective over a wide temperature range. Disclosed herein are CNT interface structures in which free CNT ends are bonded using palladium hexadecanethiolate Pd(SC16H35)2 to an opposing substrate (one-sided interface) or opposing CNT array (two-sided interface) to enhance contact conductance while maintaining a compliant joint. The palladium weld is mechanically stable at high temperatures. A transient photoacoustic (PA) method is used to measure the thermal resistance of the palladium bonded CNT interfaces. The interfaces were bonded at moderate pressures and then tested at 34 kPa using the PA technique. At an interface temperature of approximately 250° C., one-sided and two-sided palladium bonded interfaces achieved thermal resistances near 10 mm2 K/W and 5 mm2 K/W, respectively.
Selected Articles
A metallization and bonding approach for high performance carbon nanotube thermal interface materials
NanotechnologyRobert Cross, Baratunde A Cola, Timothy Fisher, Xianfan Xu, Ken Gall, Samuel Graham
2010
A method has been developed to create vertically aligned carbon nanotube (VACNT) thermal interface materials that can be attached to a variety of metallized surfaces. VACNT films were grown on Si substrates using standard CVD processing followed by metallization using Ti/Au. The coated CNTs were then bonded to metallized substrates at 220 °C. By reducing the adhesion of the VACNTs to the growth substrate during synthesis, the CNTs can be completely transferred from the Si growth substrate and used as a die attachment material for electronic components. Thermal resistance measurements using a photoacoustic technique showed thermal resistances as low as 1.7 mm2 K W − 1 for bonded VACNT films 25–30 µm in length and 10 mm2 K W − 1 for CNTs up to 130 µm in length. Tensile testing demonstrated a die attachment strength of 40 N cm − 2 at room temperature. Overall, these metallized and bonded VACNT films demonstrate properties which are promising for next-generation thermal interface material applications.
High thermal conductivity of chain-oriented amorphous polythiophene
Nature NanotechnologyVirendra Singh, Thomas L Bougher, Annie Weathers, Ye Cai, Kedong Bi, Michael T Pettes, Sally A McMenamin, Wei Lv, Daniel P Resler, Todd R Gattuso, David H Altman, Kenneth H Sandhage, Li Shi, Asegun Henry, Baratunde A Cola
2014
Polymers are usually considered thermal insulators, because the amorphous arrangement of the molecular chains reduces the mean free path of heat-conducting phonons. The most common method to increase thermal conductivity is to draw polymeric fibres, which increases chain alignment and crystallinity, but creates a material that currently has limited thermal applications. Here we show that pure polythiophene nanofibres can have a thermal conductivity up to ∼4.4 W m–1 K–1 (more than 20 times higher than the bulk polymer value) while remaining amorphous. This enhancement results from significant molecular chain orientation along the fibre axis that is obtained during electropolymerization using nanoscale templates. Thermal conductivity data suggest that, unlike in drawn crystalline fibres, in our fibres the dominant phonon-scattering process at room temperature is still related to structural disorder. Using vertically aligned arrays of nanofibres, we demonstrate effective heat transfer at critical contacts in electronic devices operating under high-power conditions at 200 °C over numerous cycles.
Photon-Assisted Tunneling in Carbon Nanotube Optical Rectennas: Characterization and Modeling
ACS Applied Electronic MaterialsErik C Anderson, Baratunde A Cola
2019
We present optical characterization and modeling of carbon nanotube (CNT) rectennas featuring multi-insulator, metal–insulator–metal tunneling diodes. The diodes use four layers of Al2O3 and ZrO2 dielectrics to obtain strong nonlinearity and highly asymmetric current density at low turn-on voltage. The CNT rectenna devices show energy conversion in the full optical spectrum (404–980 nm). We introduce the theory of photon-assisted tunneling (PAT) to model the optical behavior based on unilluminated diode characteristics. Our model shows agreement between PAT and our experimental results, and fitting suggests a wavelength-dependent optical voltage. We discuss the impact of rectenna parameters and elucidate performance limits to our CNT rectenna device.
Tunable Thermal Energy Transport across Diamond Membranes and Diamond–Si Interfaces by Nanoscale Graphoepitaxy
ACS applied materials & interfacesZhe Cheng, Tingyu Bai, Jingjing Shi, Tianli Feng, Yekan Wang, Matthew Mecklenburg, Chao Li, Karl D Hobart, Tatyana Feygelson, Marko J Tadjer, Bradford B Pate, Brian Foley, Luke Yates, Sokrates T Pantelides, Baratunde A Cola, Mark S Goorsky, Samuel Graham
2019
The development of electronic devices, especially those that involve heterogeneous integration of materials, has led to increased challenges in addressing their thermal operational temperature demands. The heat flow in these systems is significantly influenced or even dominated by thermal boundary resistance at the interface between dissimilar materials. However, controlling and tuning heat transport across an interface and in the adjacent materials has so far drawn limited attention. In this work, we grow chemical vapor-deposited diamond on silicon substrates by graphoepitaxy and experimentally demonstrate tunable thermal transport across diamond membranes and diamond–silicon interfaces. We observed the highest diamond–silicon thermal boundary conductance (TBC) measured to date and increased diamond thermal conductivity due to strong grain texturing in the diamond near the interface. Additionally, nonequilibrium molecular dynamics simulations and a Landauer approach are used to understand the diamond–silicon TBC. These findings pave the way for tuning or increasing thermal conductance in heterogeneously integrated electronics that involve polycrystalline materials and will impact applications including electronics thermal management and diamond growth.
Thermal radiation in systems of many dipoles
arXiv preprint arXiv:1906.10003Eric J Tervo, Mathieu Francoeur, Baratunde A Cola, Zhuomin M Zhang
2019
Systems of many nanoparticles or volume-discretized bodies exhibit collective radiative properties that could be used for enhanced, guided, or tunable thermal radiation. These are commonly treated as assemblies of point dipoles with interactions described by Maxwell's equations and thermal fluctuations correlated by the fluctuation-dissipation theorem. Here, we unify different theoretical descriptions of these systems and provide a complete derivation of many-dipole thermal radiation, showing that the correct use of the fluctuation-dissipation theorem depends on the definitions of fluctuating and induced dipole moments. We formulate a method to calculate the diffusive radiative thermal conductivity of arbitrary collections of nanoparticles; this allows the comparison of thermal radiation to other heat transfer modes and across different material systems. We calculate the radiative thermal conductivity of ordered and disordered arrays of SiC and SiO2 nanoparticles and show that thermal radiation can significantly contribute to thermal transport in these systems. We validate our calculations by comparison to the exact solution for a one-dimensional particle chain, and we demonstrate that the dipolar approximation significantly underpredicts the exact results at separation distances less than the particle radius.
