1. Research: http://www1.mengr.tamu.edu/mpf/
NANO-DEVICES FOR ENHANCED COOLING, STORAGE AND SENSING
Debjyoti Banerjee, Ph.D.
Morris Foster Faculty Fellow (2007-2009) and Assistant Professor of Mechanical Engineering;
Faculty Fellow, Mary Kay O'Connor Process Safety Center;
ASEE Faculty Fellow, SPAWAR/ Office of Naval Research (ONR) 2009
Mail Stop 3123, Texas A&M University, College Station, TX 77843-3123.
Ph: (979) 845-4500, Fax: (979) 845-3081 Email: dbanerjee@tamu.edu
ABSTRACT:
Our research combines: (a) cooling and thermal storage technologies with (b) nano-technology.
In the thermal area – we are investigating micro-scale heat transfer phenomena in boiling.
Micron-scale features in boiling cause the formation of “cold spots”. These cold-spots are able to
transmit almost 60-90% of the total heat transfer. Using Carbon Nano-Tube coated surfaces cooling
was enhanced by 30-300%, probably due to enhancement of these cold spots in boiling. Using silicon
nano-fins - cooling was enhanced by 120%. The applications are in materials processing and thermal
management (cooling). We have also demonstrated cooling enhancement by ~8-30% using nanofluids.
We are currently exploring the use of nanofluids for solar thermal energy conversion.
DPN™ (Dip Pen Nanolithography) is a versatile technology that leverages microfluidic ink
delivery systems with Scanning Probe Microscopy. In earlier studies the DPN process was enhanced
through the development of commercial microfluidic devices called “Inkwells™”. We are currently
developing the next generation microfluidic devices for DPN (e.g., Fountain Pen Nanolithography).
The applications are in nano-catalysis, combinatorial nano-synthesis, bio-nanotechnology (e.g., cancer
nanotechnology), maskless-lithography and nano-sensors for homeland security, bio-security and
explosives detection (e.g., “nano-nose” and “nano-tongue”). We have invented a process for
synthesizing Carbon Nanotubes of a single chirality (either metallic or semi-conducting) using DPN.
Biography: Prior to Texas A&M University, Dr. Banerjee worked as a Manager of Advanced Research &
Technology (ART) group at Applied Biosystems Inc. ($2B annual revenue), CA, where he
managed a group of 10 engineers and scientists (6 Ph.D.). Previously in a singular capacity,
Dr. Banerjee developed from concept to a commercial product at NanoInk Inc. (called
“InkWells™). Inkwells are microfluidic platforms used for bio/nano-technology applications.
Dr. Banerjee has 2 issued patents, submitted 4 provisional patent applications, while working
at ABI, Ciphergen Biosystems, NanoInk and Coventor Inc. Dr. Banerjee received his Ph.D. in
Mechanical Engineering from UCLA (with minor in MEMS) and received the “2001 Best
Journal Paper Award” from the ASME Heat Transfer Division (HTD). He received 3 M.S.
degrees and was invited to 4 national honor societies. He attended the Indian Institute of Technology (IIT),
Kharagpur for his Bachelor of Technology (Honors). At the graduation convocation at IIT he received the
“Amlan Sen Best Mechanical Engineering Student Award (Endowment)”. He also received the “Jagdish Bose
National Science Talent Scholar” award from the Government of India. Dr. Banerjee received the “New
Investigator Award (2005)” from the Texas Space Grants Consortium (TSGC), the “ASEE/AFOSR Summer
Faculty Fellowship (2006, 2007)” at AFRL, the “ASEE/ONR Summer Faculty Felloship” at SPAWAR, “Morris
Foster Fellowship (2007-2008)” from Mechanical Engineering Department at Texas A&M University and was
designated as a Faculty Fellow at the Mary Kay O’Connor Process Safety Center at the Texas A&M University.
He received the “3M Corporation Non-Tenured Faculty Fellowship (2009-2012). Dr. Banerjee’s research
interests are in thermo-fluidics (boiling, nanofluids), solar thermal energy, MEMS/ microfluidics and
nanotechnology (DPN, nano-synthesis and bulk synthesis of CNT and graphenes).
Research Sponsors/ Collaborators: NSF, DARPA, SPAWAR, US Air Force (AFRL, AFOSR), Navy (ONR), Army
(ARO), Texas Space Grants Consortium (TSGC), NASA (URETI/TiiMS), Nano-MEMS Research, DOE, Qatar National
Research Foundation (QNRF), Lynntech, Aspen Thermal System, Irvine Sensors, Anteon Corp (General Dynamics),
General Electric – Corporate Research & Development (GE-CRD), 3M Corp.
Page 1 of 6 Ph: (979) 845-4500, Fax: (979) 845-3081 Email: dbanerjee@tamu.edu 03/13/2009

2. BOILING ON NANO-STRUCTURED SURFACES
30 - 300% Enhancement in Cooling
18
Bare Silicon Saturation Bare Silicon 5 ºC Subcooled
Type‐A Saturation Type‐A 5 ºC Subcooled
16 Type‐B Saturation Type‐B 5 ºC Subcooled
14
Height of CNT
Averaged Heat Flux (W/cm )
2
12 Type A: 9 microns
Type B: 25 microns
10
8
6
4
2
0
0 10 20 30 40 50 60 70 80 90
Wall Superheat (ºC)
Figure 1. Boiling on Carbon Nanotube (CNT) coated silicon wafer for PF5060
refrigerant. The results show a 30-300% enhancement in heat transfer. Experiments
were performed in the research group of PI. (ASME J. Heat Transfer, 2006; 2008).
120% Enhancement in Cooling
Nucleate Boiling Curve for qn" (W/cm2)
30
ΔTSub = 0 C
o
25
Heat flux (W/cm )
2
20
15
10
5
0
2 4 6 8 10 12 14
Wall Superheat (oC)
100 nm Run1 100 nm Run2 336 nm Run1 336 nm Run2
259 nm Run1 259 nm Run2 Bare
Figure 2. Boiling on Silicon Nanofins. Pool boiling heat flux was enhanced by ~120% on
heaters with silicon nano-fins (SEM of nanofins shown in inset). Silicon nano-fin geometry:
~100 nm height, ~200 nm diameter, .~800 nm pitch (ASME-IMECE 2007).
Page 2 of 6 Ph: (979) 845-4500, Fax: (979) 845-3081 Email: dbanerjee@tamu.edu 03/13/2009

3. TEMPERATURE MICRO/NANO-SENSORS FOR BOILING MEASUREMENTS
(a) (b) (c)
Figure 3. SEM images of (a, b) Thin Film Thermocouples (TFT), integrated with
(c) Carbon Nanotubes (CNT): The CNT structures are 9-25 microns in height and 8-16
nm diameters. The integrated device was used to study transport mechanisms in pool
boiling. Heat transfer enhancement of ~30-300% was achieved. (J. Heat Transfer, ’06)
Thermocouple Junction Chromel Alumel Figure 4. Temperature Micro-sensors:
Thin Film Thermocouples (TFT)
(a) Mask Layout, and (b) Fabrication
(using photolithography, physical vapor
deposition, and lift-off process) on
silicon and pyrex wafers. K-Type was
chosen for their sensitivity and broad
linearity. The Chromel and Alumel layers
are ~200nm thick, ~ 30microns wide and
the junctions are on 200 microns pitch.
Bond Pads (a) Bond Pads (b) (J. Components & Packaging Tech., ‘06)
8
7
6
COLD SPOT
5
Power
4
3
2
1
Cold Spot 0
0 5 10 15 20 25 30
Frequency [Hz]
(a) (b)
Figure 5. Cold Spot: (a) Simulation results showing “cold spot” dynamics in boiling of water
on a steel heater. This received the “Best Journal Paper Award” from the ASME Heat
Transfer Division. The animation movies can be downloaded from PI’s research website.
Wire frame depicts vapor bubble. Heat Flux = 1.68 W/cm2. (Banerjee and Dhir, ASME-IMECE
’96; J. Heat Tr. ’02). Color Code: Red: High, Blue: Low temperature.
(b) Fast Fourier Transform (FFT) of temperature fluctuations recorded from pool boiling
experiments using surface micro-machined temperature micro-sensors (thin film
thermocouples). The FFT data shows frequency peaks in temperature in the 10-15 Hz range
– showing the existence of “cold spots”. (AIAA Paper No. 06-5586).
Page 3 of 6 Ph: (979) 845-4500, Fax: (979) 845-3081 Email: dbanerjee@tamu.edu 03/13/2009

4. NANOFLUIDS FOR ENHACNED COOLING & MOLECULAR DYNAMICS
220
Heat Flux vs Flowrate (400W)
215
210
Heat Flux (W/m2)
205
200
195
190
Nano (0.6%)
Nano (0.3%)
185
PAO
180
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Flowrate (gpm)
(a) (b)
Figure 6. Nanofluids in Fin Cooler (a) Experimental apparatus showing the gap fin cooler.
(b) Heat flux enhanced by upto 10% for nanofluids using exfoliated graphite particles in Poly
Alpha Olefin oil (PAO) for concentrations of 0.6% and 0.3%. Inset: SEM of the precipitated
nano-particles from the nanolfuid on to the heater surface leading to “nano-fin” effect which
causes enhancement in heat flux (AIAA J. Thermophysics, 2008).
200
Reservoir 200 W Input
150
Heat Rejection (W)
Liquid-Liquid
Finned Heater Compact Heat
Exchanger
100
Hot Loop (Oil) Cool Loop
(Water)
50 Nanofluid
PAO
0
Flowmeter Magnetic Gear 0 0.25 0.5 0.75 1 1.25 1.5 1.75
Pump Flowrate (gpm)
Figure 7. Nanofluids in Compact Heat Exchangers. (a) Compact heat exchanger
apparatus. (b) Heat flux enhanced by 30% for nanofluids using Carbon Nanotube (CNT) in
Poly Alpha Olefin oil (PAO) for concentrations of 0.6%. Inset: Inset: SEM of the precipitated
nano-particles from the nanolfuid on to the heater surface leading to “nano-fin” effect which
causes enhancement in heat flux. (AIAA J. Thermophysics, 2008, in preparation)
4
SWNT & Water Figure 8. Molecular Dynamics simulation of
SWNT & Water + CuO
nanofins and nanofluids. (Inset) Unit cell with
3
water and CuO nanoparticles in contact with
Rk x10 -8 m2K/W
nanofin. Interfacial resistance (Kapitza
2 resistance) for water and CuO nanofluid changes
in contact with the nanofluid. (Int. J. of Thermal
1 Sciences, 2009)
0
400 600 800 1000 1200
Nanotube Temperature (K)
Page 4 of 6 Ph: (979) 845-4500, Fax: (979) 845-3081 Email: dbanerjee@tamu.edu 03/13/2009

5. MICROFLUIDICS FOR BIO/NANO-LITHOGRAPHY
(a) (b)
(c) (d) (e)
Figure 9. Inkwells™: Microfluidic ink delivery apparatus for Dip Pen Nanolithography of 4-10
inks. (a) Inkwell for nano-bio lithography applications in genomics. (b), (c): Inkwell for nano-
bio lithography applications in proteomics. (b), (c), (d) Scanning probes in registry with
microwells for “ink-loading” step in DPN. (e) Computational results for meniscus bifurcation
studies in capillary driven microfluidics. (SPIE J. of Micro/Nano-Fabrication, “MF3”, 2006).
(a)
(b) (c)
Figure 10. Centiwells: Microfluidic apparatus for simultaneous nano-patterning of ~100
species by Dip Pen Nanolithography (DPN). (a) SEM image of Centiwells containing
polystyrene micro-beads. (b) Scanning probe on an Atomic Force Microscope dipped in PEG
solution in the micro-wells. (c) LFM image of fractal nano-patterns formed by DPN of PEG.
(SPIE J. of Micro/Nano-Fabrication, “MF3”, 2007).
Page 5 of 6 Ph: (979) 845-4500, Fax: (979) 845-3081 Email: dbanerjee@tamu.edu 03/13/2009

6. NANO-SENSORS FOR EXPLOSIVES DETECTION (HOMELAND SECURITY)
Laser Explosives Micro-Heater (Gold)
Source Sensor
Reaction
Surface (Gold)
Laser Ray
Activated
Silicon Micro-Cantilever
Base (Silicon Nitride)
Detector
Sensor System
Explosives Sensor (Nano-Calorimeter)
(a) (b)
Figure 11. (a) Schematic of explosive sensor using nano-calorimetry. (b) Micro-heaters
maintain cantilevers at the ignition temperatures of the explosives to be detected.
In presence of an explosive the micro-cantilever at the corresponding ignition
temperature is activated. Multiple cantilevers can be maintained at same temperature for
eliminating false positives. Each micro-cantilever can be maintained at a specific temperature
or scanned over a range of temperatures for detecting multiple explosives. Nominal
dimensions Micro-cantilever: 150 × 25 microns, 100nm thick, Pitch: 30 microns; Micro
Heaters: 25 × 22 microns, 100 nm thick, gold; Reaction surface: 10nm, gold.
Explosives Sensor
Sensor Response (Summary)
250 500
Vapor Pressure (mm of Hg)
Ignition Temperature (C)
200 Gasoline 400
V a p o r P re s s u re ( m m o f H g )
Ig n it io n T e m p e ra t u re ( C )
Acetone
150 300
100 200
50 100
Iso-Propyl Alcohol
0 0
5 15 19
Micro-Heaters Sensor Threshold Current (mA)
(a) (b)
Figure 12. (a) Heated micro-cantilever array for explosives detection (by nano-calorimetry).
Experimental results showing unique sensor response (signatures) under ambient conditions
for several explosives: gasoline, acetone, alcohol. (Defense & Security Symp.’06, SPIE 6223-24).
Page 6 of 6 Ph: (979) 845-4500, Fax: (979) 845-3081 Email: dbanerjee@tamu.edu 03/13/2009