Development and Testing of a Micro- Cantilever Based Nano ...

[[email protected]]Multi-Phase Flows and Heat Transfer Lab. 1 of 22

2010 Mary Kay O’Connor Process Safety Center International Symposium

Development and Testing of a Micro-Cantilever Based Nano-Calorimeter for

Explosives Detection

S.-W. Kang, H. Kefeni (Ph.D. Students), and D. Banerjee (Ph.D.)

Multi Phase and Heat Transfer Lab.

Department of Mechanical Engineering

Texas A&M University

Oct. 27th, 2010



Introduction

Micro-cantilever based sensing system

– Detection of Explosives

– PH Sensing

– Disease Sensing

– DNA Hybridization

Two operation modes

– Static Mode (i.e. change in deflection)

– Dynamic Mode (i.e. natural frequencies)



Electronic-nose

MEMS system to mimic bomb-sniffing dogs → “Artificial nose”

– Electric power system

– Chemical sensing system

– Response detection system

Explosive gas sensing is performed by recognizing molecules by the measurement of changes in bending response.



Sensing Mechanism

The absorption or surface reaction of explosives on electrically pre-heated micro-cantilevers causes variations in thermal stress at the surface (Chemo-Mechanical Sensing)

→ Redistribution of the electronic chargeRepulsion bet. molecules→ Compressive surface stress→ Downward / Negative Deflection

Attraction bet. molecules→ Tensile surface stress→ Upward / Positive Deflection



Numerical Modeling (1)

Proper estimation of the temperature profile is a key factor in our nano-calorimeter platform.

The coupled electro-thermo-mechanical analysis is achieved by coupling of a CFD tool (Fluent ®) and an FEA tool (Ansys ®).



Numerical Modeling (2)

Joule Heating(UDF)

Species Transport &Gaseous

Combustion

Static Structural

CFD/FEA Thermal

Coupling (UDF)

CFD(FLUENT ®) CFD(FLUENT®) FEA(ANSYS®)



Joule Heating (UDF)

Fluent does not provide the solution for joule heating, so we implanted the user-defined function (UDF).

2 2 lQ I R I

A

2I

qA

(Volumetric Heat Generation Rate)

Temperature Profile heated by electrical

current (20mA)

Fluent Simulation Using UDF

ANSYS Simulation UsingElectro-Thermo Multiphysics



Gaseous Combustion

Concentration of reactants need to be specified on a basis of mass fractions.

– ‘Laminar finite-rate model’ is used.

– The rate constant is expressed in an Arrhenius form.

Chemical kinetics of explosives is obtained from the literatures.

/r rE RTrk A T e



Chemical Kinetics (VOC)

The multiple-step combustion model gives a more optimized value.

Reaction Ar βr Er

2C3H6O + 5O2 → 6CO + 6H2O[7-8] 1.9 × 1011 -1.0 2.09 × 108

2H2 + O2 → 2H2O[7-8] 2.37 × 10-3 -0.5 8.79 × 107

2CO + O2 → 2CO2[7-8] 3.55 × 105 -1.5 8.79 × 107

CO + H2O → CO2 + H2[7-8] 1.2 × 108

3.73 × 109

-1.0-1.0

1.74 × 108

2.06 × 108

C3H7OH → C3H6 + H2O[9] 8.32 × 107 0.0 8.11 × 107

C3H7OH + 1/2O2 → C3H6O + H2O[9] 4.58 × 107 0.0 7.16 × 107

C3H6 + 9/2O2 → 3CO2 + 3H2O[9] 6.75 × 109 0.0 9.57 × 107

C3H6O + 4O2 → 3CO2 + 3H2O[9] 1.39 × 1020 0.0 2.103 × 108



Case Setup & BC

3-D, Laminar, Species Transport, Surface Reaction and Steady-state Simulation

– Hexagonal, Gradient meshing technique

– Number of Grids: 590, 940

– Aspect Ratio < 0.12

(99%); Maximum=0.48

Constant Mass Fraction in Chamber at a state of dynamic equilibrium

(depends on the evaporation pressure)



CFD/FEA Thermal Mapping

It should be ensured that the scaling of the model is consistent in Fluent® and Ansys ®.

Solid Model of Bimorph Microcantilever in Gambit

Solid Model of Bimorph Microcantilever in ANSYS



Chemo-Mechanical Response

1. Electrically pre-heated bimorph MCL

2. Thermal response to combustion of VOC (Acetone) at the surface of MCL

3. Resultant deflection by bimetallic effect

Temperature CO2 Mass Fraction H2O Mass Fraction

Temperature

Applied Current = 20 mA (Acetone: CH3COCH3)

20 mA

δ = 9.39 μmδ = 38 μm



Chemo-Mechanical Response

1. Electrically pre-heated bimorph MCL

2. Thermal response to combustion of VOC (Isopropanol) at the surface of MCL

3. Resultant deflection by bimetallic effect

Temperature CO2 Mass Fraction H2O Mass Fraction

Temperature

20 mA

δ = 9.39 μmδ = 38 μm

Applied Current = 20 mA (Iso-propyl Alcohol: C3H7OH)



Change in Deflection

The change in surface temperature due to combustion contributes to the differences in deflections caused by the bimetallic effect.



Optical Deflection Detection

The deflection is experimentally measured by tracking the light spot reflected from the micro-cantilever surface.

Advantage→ sub-nanometer resolution

Disadvantage→ alignment system is expensive

Materials Today, 2007



Experimental Apparatus

Air-tight acrylic chamber

Platform to support and control the movement of the laser and micro-cantilevers.



Threshold Current

The threshold current can be estimated from the self-ignition temperature.

Ammonium Nitrate, Picric AcidAmmonium Picrate

TNT

RDX

AcetoneIsopropyl Alcohol

EGDN

Picramic Acid

In the case of VOC, the dependence of the

evaporation pressure and catalytic oxidation should be considered.



Summary and Conclusion

In this study, the static response of a microcantilever in the presence of explosives were characterized experimentally and by performing numerical simulations.

The sensor sensitivity can be enhanced by specifically coating the high thermal conductivity materials onto the micro-cantilever surfaces (e.g. using Dip-Pen Nanolithography: DPN).



Acknowledgements AFRL/AFOSR: ASEE Summer Faculty Fellowship (RZ), RX NSF (SGER Program, SBIR Program): Dr. Al Ortega ONR (Thermal Management Program): Dr. Mark Spector SPAWAR: Dr. Richard Nguyen, Dr. Ryan Lu DARPA (MTO, MF3 Center) DOE (Solar Energy Program) NASA (URETI/ TiiMS) JPL (Jet Prpulsion Lab.): Dr. Anu Kaul TSGC (Texas Space Grants Consortium) TEES (Texas Engineering Experimentation Station) Mechanical Engineering Dept., Texas A&M (New Faculty Start-Up Grant) Industry Collaborators:

– ESI Group: CFD-ACE+– 3M Corp.– Nano-MEMS Research (NSF SBIR Phase I, AFOSR STTR Phase I & II),– Aspen Thermal Systems (ONR SBIR Phase I),– Lynntech Inc. (ARO SBIR Phase II)– Irvine Sensors (AFOSR SBIR Phase II)– General Dynamics (Anteon Corp.): AFRL Seed Grant– General Electric (GE): Global Research Center, NY– NanoInk Inc.: MEMS Group (Campbell, CA)



Acknowledgements

DOE Solar EnergyTechnology Program (NREL, Golden, CO): – Brian Hunter, Allie Aman, Craig Turchi, Ryan Shininger, Brad Ring

ONR (SPAWAR, San Diego, CA): – R. Nguyen PhD, R. Lu PhD, A. Ramirez PhD

AFRL (WPAFB, Dayton, OH):– R. Ponnappan, Ph.D. (AOARD), – R. Naik, Ph.D., J. Slocik, L. Brott (RX), – Ajit Roy, Ph.D., S. Ganguly, Ph.D. (RX), Dr. L. Gschwender (RX), Dr. Ed Snyder (RX)– K. Yerkes, Ph.D. , T. Michalak, A. Flemming (RZ)

DARPA (MF3 Center): 12 universities, 20 faculty, 9 companies, 1 National Lab.– George Whitsides (Harvard)– Luke Lee, Liwei Lin (UC Berkeley)– Juan Santiago (Stanford)– Marc Madou, Bill Tang, Abe Lee, Mark Bachman, Robert Corn, M. Khine, Jim Brody (UCI)– Steve Werely (Purdue)– Hugh Fan (University of Florida)– Jeff Wang (Johns Hopkins)– Tianghong Cui (U. Minnesota)– David Beebe (U. Wisconsin)– Ian Pappuatsky (U. Cinncinnati)



U. New Haven: S. Sinha, Ph.D., U. Texas (Austin): S. Banerjee, Ph.D. U. Texas (Dallas): R. Baughman, Ph.D., U. Maryland (UMD): J. Kim, Ph.D.

3M: Phil Tuma General Electric (GE-CRD): L. Tsakalocos, Ph.D. Lynntech: T. Ragucci, T. Gilletto, Ph.D. Nano-MEMS: H.J. De Los Santos, Ph.D. Irvine Sensors: Ying Hsu, I. Sapir Aspen Thermal Systems: Steve Casey, Tom Lovell NanoInk Inc.: J. Fragala

Industry Partners (MF3 Center) ESI Group Beckman Coulter, Inc. Douglas Scientific Monsanto Company Pioneer Hi-Bred International, Inc. Invitrogen Irvine Sensors Corporation Lawrence Livermore National Laboratory

Acknowledgements



Debjyoti ( “DJ”, “Deb”) Banerjee3123 TAMU, Texas A&M

Mechanical Engineering

College Station

TX 77843-3123

Ph: (979) 845-4500

Fax: (979) 845-3081

Email: [email protected]

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Technologies

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