Detection of Explosives using Portable Devices ...ansoaindia.in/disha2013/images/pdf/ProfSoumyoMukherjee.pdf · Detection of Explosives using Portable Devices Developments in the

Detection of Explosives using Portable Devices

Developments in the Indian Context

Soumyo Mukherji

Department of Biosciences and Bioengineering

IIT Bombay

S. Mukherji, IIT-Bombay ([email protected])

Introduction

• Challenges In Explosive Detection

o Broad range of explosives

o Low vapor pressures and concentrations of explosives

o Minute quantities available

o Aggressively bind to surfaces

o Separation from background

o Presently available explosive detection - bulky and expensive

o Economic implications of widescale deployment

o Systems required that are small, portable, inexpensive

o Should have high SNR, low power consumption

o Should be able to give on-site analysis thus have local data processing


The Schemes of Detection

David S. Moore, Recent

Advances in Trace

Explosives Detection

Instrumentation, Sens

Imaging (2007) 8:9–38


Content of this talk

• Few examples from many systems are are being used/developed.

• IMS, GC-MS, NQR, THz, etc. technologies : some already developed and in commercial use and some others being developed does not yet show the promise of being affordable for widescale use.

• MEMS based sensors (Microcantilevers and Microheaters)

• Fluorescence Quenching Polymers

• Optical Sensors


The Problem of Very Low Vapor Pressures

This gives the basis for the interest in RDX particle detection. A 10 micron speck of RDX will weigh about 1.5 ng and have approximately 4x1012

molecules (equivalent to 1.5 L of saturated air at 37C)

Vapor pressure versus temperature

curves for a number of common

explosives and related materials.

The solid lines are the experimentally

measured temperature ranges; the

dashed lines are extrapolations

David S. Moore, Recent Advances in Trace

Explosives Detection Instrumentation, Sens Imaging

(2007) 8:9–38


Bulk Detection

• The CTX explosive detection device uses CAT scans and sophisticated image processing software to automatically screen checked baggage for explosives.

• Various variants of this and competitors are found in airports.

• Based on shape recognition.


Terahertz

• Significant interest in employing terahertz (THz) technology, spectroscopy and imaging for security applications.

Detect concealed weapons since many non-metallic, non-polar materials are transparent to THz radiation;

Explosives have characteristic THz spectra

THz radiation poses no health risk for scanning of people.


Bulk Detection Systems


Bulk Detection Systems


IMS

• Similar to Time-of-Flight MS.

• Uses soft ionization by atmospheric-pressure chemical ionization. Sample material is heated to yield a vapor that is swept into a small drift chamber where a beta radiation source ionizes the molecules.

• Ionized molecules travel through a drift tube under a weak electric field at distinct speeds that are related to their mass and geometry and hit a detector. Selectable positive and negative ionization enhances identification or sensitivity.

• The distribution of these signals forms an ion spectrum, with an ion mobility band corresponding to each of the unique ionic species. The spectrum is a fingerprint of the parent compound.


IMS (Ion Mobility Spectrometry)

Commercial IMS technology manufacturedby Smiths Detection; • top left, a Sabre 4000 hand-held

instrument,• right, the Sentinel, a personnel portal • bottom left, an Ionscan 400B

benchtop instrument.

Ion trap mobility spectrometers (ITMS), which is an IMS-based technology from GE Security. • Top left, the VaporTracer2 hand-held instrument; • right, the EntryScan3, a personnel portal; • bottom left, the Itemiser3, a benchtop instrument


Chemiluminescence Detectors

• Most common explosives materials contain nitrogen (N) in the form of either nitro (NO2) or nitrate (NO3) groups.

• Chemiluminescence reaction scheme for explosives detection involves infrared radiation (IR) light emission from excited-state nitrogen compounds.

• All that can be said is that a nitrogen-containing molecule was present that decomposed to yield NO, and such molecules are found in explosives and taggants but also in fertilizers, some perfumes, and other common materials.

• So a GC Column is typically fixed on the front end


Different Trace Detection systems

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The Divining Rod… The Pendulum of Prof. Calculus (of Tintin fame) ????

Variety of names :

Sniffex

GT200

ADE651

Quadro

http://cache.gawkerassets.com/assets/images/4/2010/01/iraq.jpg

http://cache.gawkerassets.com/assets/images/4/2010/01/iraq.jpg


Trace Detection on Surfaces

• Cymantrene embedded in a polymer and developed using UV radiation shows change of color on exposure to explosives : Colorimetry.

• Desorption electrospray ionization (DESI) and desorption atmospheric pressure chemical ionization (DAPCI) have been used as sensitive and selective ionization methods for MS analysis of surface materials. This may be used with MEMS devices as well.


Separate and Test

• Gas Chromatography coupled with a SAW detector.

o short high efficiency columns, where the GC analysis only takes a few seconds.

o A 1-m long resistively heated capillary column was coupled to an uncoated solid-state crystal SAW detector [ Staples & Viswanathan]. Heating rates up to 20C/s produced 10-s chromatograms with peak widths of a few ms.

• Detection has been demonstrated using arrays of SAW devices with different coatings.


Selective Coatings

• Biochip for TNT detection

o Larsson and colleagues

o Self-assembled monolayers (SAMs) of hydroxyl-terminated oligo(ethylene glycol)-thiols

o Surface plasmon resonance (SPR) or quartz crystal microbalance (QCM) transduction .

• Field effect transistors (FET) based on organic materials.

o Nitroaromatic molecules bind to the thin organic films, which form the transistor channel

o This increases film conductivity and changes the transistor electrical characteristic


Selective Coatings (contd.)

• 4-mercaptobenzoic acid (4-MBA) on Cantilevers

o Pinnaduwage and collaborators

o Commercial piezoresistive microcantilever arrays

o SAM of 4-MBA acts as a hydrogen bonding coating for analytes.

o LOD in the parts per trillion range, but no selectivity.

• Metalloporphyrins on QCM

o Porphyrins with particular metal core have been shown to selectively adsorb explosive molecules (RDX, TNT)

o QCM-s are piezoelectric crystal based instruments in which very slight mass changes (pg to fg) can be detected on the basis of vibrational frequency changes of the piezo-crystal on which the analyte adsorbs.


MEMS and Microcantilevers

• Significant work being done in ORNL and UC Berkeley

• Thundat group on ORNL and Majumdar’s group in UCB


Cantilever Arrays and Pattern Recognition

Response patterns of an array of six cantilevers each coated with a different SAM (columns A-F) when exposed to vapors of TNT, ethanol, acetone, and water. Each column shows the 80 s bending response (see Fig. 3) of one cantilever/coating (A-F) when exposed to each of the four analytes. These response patterns have to be analyzed with a pattern recognition algorithm.


PETN on Cantilevers


Comparison of Explosives and Non-explosives


Detection without Special Coatings

• Pinnaduwage and colleagues detected TNT deposited on a pulse-heated piezoresistive microcantilever via deflagration induced bending and resonance frequency shifting.

Deflagration response. As the cantilever

exposed to an explosive is heated, its

temperature first lags behind the temperature

of the reference cantilever (no explosives)

because of the increased thermal load. Then

as the explosive reaches the deflagration

temperature, the exothermic process causes

the temperature of the loaded cantilever to

increase and exceed that of the reference

cantilever. As the explosive leaves the

cantilever, the temperature returns to that of

the reference cantilever.

Nanosensors for trace explosive detection, Larry Senesac and Thomas

G. Thundat, Materials Today, March 2008


Photothermal Deflection Spectroscopy

When a bimaterial cantilever that is exposed to TNT is sequentially illuminated with infrared (IR) radiation, the cantilever bends as the adsorbed TNT molecules absorb the energy. The plot of the bending as a function of the IR wavelength creates a mechanical IR absorption spectrum of TNT.

Nanosensors for trace explosive detection, Larry Senesac and Thomas

G. Thundat, Materials Today, March 2008


Research Efforts at IIT Bombay

Essentially a group effort, with different faculty members of the group targeting specific methods.

• Fluorescence Quenching Polymers (Anil Kumar)

• Microcantilevers (R. Rao and S. Mukherji)

• Deflagration or Heat Absorption on suspended Microheaters (S. Mukherji and R. Rao)

• Optical – Localized Surface Plasmon Resonance (S. Mukherji)


Adv. Polym. Sci. 2005, 177, 151.

Amplified Fluorescence Polymers


DARPA Dog’s Nose program

Objective: Match Canine Landmine

Detection Performance

Swager/MIT: Chemical Technology

Nomadics: Instrumentation, Operations

and Systems Development

Nomadics developed Fido, the only successful TNT sniffer.

http://www.chemicalagentdetection.com/presentations/paul.pdf

Nomadic: Vapor detection of TNT


0

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0 100 200 300 400 500 600 700

DI/

I

Concentration

Fluorescence Quenching sensitivity with TNT

Fluorescence quenching as a function of concentration for three molecules

(DB, ADI, ADB) developed at IIT Bombay (courtesy Prof. Anil Kumar)

ADI

ADB

DB

The sensitivity of ADI and ADB is observed to be almost the same.


Explosive Detection based on Fluorescence Quenching (from Prof. Anil Kumar)

Polymer on silica gel without

TNT

Polymer on silica gel with

TNT

WHITE LIGHT


Explosive Detection based on Fluorescence Quenching (from Prof. Anil Kumar)

Polymer on silica gel

without TNT

Polymer on silica gel

with TNT

UV LIGHT (354 nm)


Setup for Detection using Quenching Polymers (from Prof. Anil Kumar)

24.5 mvDamper

Pump

Sample

Glass Rod

Fluorescent Polymer Coating

Power supply unit

Photo-detector

Multimeter

Valve

Photodiode


Device Response to TNT Vapors ((from Prof. Anil Kumar)

0 100 200 300 400 500 600 7000

1

2

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5

6

Flu

ore

sce

nce s

ign

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olts)

Time (sec)

Exposure to TNT

0 50 100 150 2000

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Flu

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Time (sec)

Response of an uncoated tube


Polymer Microcantilevers with optical transduction

Design and fabrication of SU-8 cantilevers

Fabrication methodFlip-chip approach[3 mask process]

Release layer HSQ, Sputtered SiO2

Cantilever layer SU-8 2002

Die & Frames SU-8 2100

Schematic of cantilever die attached to frame

optical and SEM micrograph of cantilever


The Portable Instrument


Results using Microcantilever


Micro – Cantilevers

• Cantilever Sensorso ~ 200um in sizeo Piezo-Resistive with electrical readouto In-house fabrication

• Material Scienceo Polymer Cantilevers with low stiffness, very high

sensitivity for gaseous phaseo Silicon Cantilevers stable in liquid medium

• Fabrication Technologieso Optical Lithographyo Chemical Vapor Depositiono Spintronics, Chemical / Plasma Etching

• Cantilever Functionalizationo Chemical Coatings with high specificity

towards surface chemistry of “Analyte”o Multi – Cantilever Arrays with higher binding

selectivity• Chemical Detection

o Bending due to molecular surface interactionand thereby produced surface stress

o Leads to change in resistance of piezo-resistive layer

o Analyte traces detected through highlysensitive dR/R instrumentation circuits


Explosive Detection

• Polymer Micro – Cantilever and MEMS based Handheld Explosive Detectors with very high sensitivity

• Trace Detection of Explosive Moleculeso Detection up to parts per billion molecules in airo All derivatives of RDX, TNT and PETNo Lab tested with up to 21 different explosive

compounds

• Low Cost Deploymento Highly cost effective for mass deployment in

Airports, Railway and Bus Stations, Hotels, Malls, Public Places

• Real Time Detection – Response in 5 to 10 seconds

• Fast boot up time, plug and play operation for cantilever sensor replacement


Third Party Testing


Detection using deflagration

• Deflagration Reaction

o Convective burning of energetic material with a large surface area.

o Rapid form of combustion with liberation of heat and gases.

• Explosive vapor heated to deflagration temp

o (RDX =260ºC, TNT=475º C)

• TNT & RDX molecules bind to the silicon dioxide surface using SiO2 – NO2 bond, particle-particle bond.

• Heat liberated sensed by RTD changing the resistance

R=R0(1+(T-T0) )

• Deviation in I-V characteristic from normal observed as a spike.


Microheater Design

• Suspended membrane : one dimensional – main heat

conduction through the suspension beams

• Total heat flow equation

Heat conduction through the

closed membrane

Heat conduction through

ambient air

Heat losses due to

radiation

Unknown heat loses

• Important points for the design of a micro heater

o Constructing thin membranes of materials having low thermal conductivity

o Use of suspension beams with high length-to-width ratio

o Decreasing the heated area

o Choosing a large pit depth of the suspended membrane


Microheater and Sensor Design

• Silicon Dioxide platform

o Area 330 micron x 330 micron. Thickness 500 nm

• Heater

o Line width 30 micron. Total length 1.01mm

• RTD

o Line Width 30 micron. Length 281 micron


Fabricated Microheaters

Fabricated Interdigitated

Microheater (New Design)


Protocol

• RDX dissolved in Acetone and drop coated on heater.

• Different concentrations of RDX solution was used (5mg/ml and subsequently halved till 0.15625 mg/ml)

• About 1.8 microlitre drop size.

• Amount of RDX deposited on heater calculated for each concentration.

• At the lowest concentration it was 5ng on the active area.

• RDX vapor generator was also used for 1 set of experiments. 1 ppm vapor for 1 hour.


Experimental Results

Before Deflagration

Active Area covered with RDX

After Deflagration

Active Area cleared of RDX

After Deflagration

Active Area cleared of RDX


Results (Output on Pulse)

Expanded output

• Heat liberated due to deflagration.

• Increase in resistance more than due to applied voltage.


Output spike for concentration of 0.15625mg/ml

Vapor Phase output (1300C, approx 1ppm)

Output spike for concentration of 0.3125mg/ml

Results (Contd.. )


Testing of Microheater for Repeatability

The differential signal of the two pulses with a concentration of 0.039mg/ml


Instrumentation for Heaters


LSPR

• Localized Surface Plasmon Resonance (LSPR) is the reason why nanoparticles or gold look red in color when suspended in water.

• The color depends on the refractive index of the micro (or nano) environment.

• If anything attaches to gold nanoparticles the color might change.

• Used this property by immobilizing gold nanoparticles on an optical fiber, coating then with 4-MBA and passing explosive vapors over the fiber.

• Preliminary stage of work


Optical system design

1 Optical source,

2 Lens in a multi axis lens positioner and lens holder

3 Microscopic objective lens connected to fiber coupler

4 Multimode fiber coupler with tilt stage

5 Fiber holder and chucks and holder

6, 7 Flow system with capillary tube of diameter 2 mm and support

stage

8 Fiber optic positioner

9 Multi axis lens positioner

10 Lens with screw for fiber optic probe mounting

1 2 3 4 5 6, 7 8, 9, 10

Spectrometer

(200 – 870 nm)

Layer of GNP on which receptors are bound

Declad fiber exposing core


Response to TNT vapors: 4-MBA

functionalized probe

Real time detection of Explosive vapors

Response to RDX vapors: 4-MBA

functionalized probe

L-Cysteine modified probes


ASTM Standard test

• 23 L of TNT solution in IPA (1mg/L) i.e. 23 ng of TNT dispensed on Whatman filter paper and solvent allowed to evaporate completely.

• Filter paper held near the sensor head while air was sucked in.

• Regenerated by sucking dry air over sensor head.


Acknowledgements

Colleagues and Collaborators

Prof. V. R. Rao (IIT B)

Prof. Anil Kumar (IIT B)

Dr. Vasudeva Rao (IGCAR)

Dr. Gnanasekaran (IGCAR)

Dr. Jayaraman (IGCAR)

Dr. Girish Phatak (CMET)

Funding Agencies and PRMC

Dr. Chidambaram (PSA to PM)

Dr. Baldev Raj (Dir, IGCAR)

Mr. Neeraj Sinha (PSA’s office)

Students

Prasanth Sankar, Vibhor Khanna, A.V. Prasad, G. Suresh (Microheater)

N. Kale, Ms. Seena V (Cantilevers)

Jasmine (Quenching Polymers)

Reshma Bharadwaj, Simon Feyles (LSPR)




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Detection of Explosives using Portable Devices ...ansoaindia.in/disha2013/images/pdf/ProfSoumyoMukherjee.pdf · Detection of Explosives using Portable Devices Developments in the