Detection of Explosives using Portable Devices Developments in the Indian Context Soumyo Mukherji Department of Biosciences and Bioengineering
IIT Bombay
Introduction •
Challenges In Explosive Detection o o o o o
o o o o o
Broad range of explosives Low vapor pressures and concentrations of explosives Minute quantities available Aggressively bind to surfaces Separation from background
Presently available explosive detection - bulky and expensive Economic implications of widescale deployment Systems required that are small, portable, inexpensive Should have high SNR, low power consumption Should be able to give on-site analysis thus have local data processing S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
The Schemes of Detection
David S. Moore, Recent Advances in Trace Explosives Detection Instrumentation, Sens Imaging (2007) 8:9–38
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Content of this talk •
Few examples from many systems are are being used/developed.
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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 •
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
The Problem of Very Low Vapor Pressures 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
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)
David S. Moore, Recent Advances in Trace Explosives Detection Instrumentation, Sens Imaging (2007) 8:9–38
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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. •
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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. S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Bulk Detection Systems
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Bulk Detection Systems
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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.
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
IMS (Ion Mobility Spectrometry) Commercial IMS technology manufactured by 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
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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 •
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Survey of Commercially Available Explosives Detection Technologies and Equipment 2004 Author(s): Lisa Thiesan, David Hannum, Dale W. Murray, John E. Parmeter
Different Trace Detection systems
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
The Divining Rod‌ The Pendulum of Prof. Calculus (of Tintin fame) ????
Variety of names : Sniffex GT200 ADE651 Quadro
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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.
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Separate and Test •
Gas Chromatography coupled with a SAW detector. o
o
•
short high efficiency columns, where the GC analysis only takes a few seconds. 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.
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Selective Coatings •
Biochip for TNT detection o o
o
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Larsson and colleagues Self-assembled monolayers (SAMs) of hydroxyl-terminated oligo(ethylene glycol)-thiols Surface plasmon resonance (SPR) or quartz crystal microbalance (QCM) transduction .
Field effect transistors (FET) based on organic materials. o
o
Nitroaromatic molecules bind to the thin organic films, which form the transistor channel This increases film conductivity and changes the transistor electrical characteristic
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Selective Coatings (contd.) •
4-mercaptobenzoic acid (4-MBA) on Cantilevers o o o o
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Pinnaduwage and collaborators Commercial piezoresistive microcantilever arrays SAM of 4-MBA acts as a hydrogen bonding coating for analytes. LOD in the parts per trillion range, but no selectivity.
Metalloporphyrins on QCM o
o
Porphyrins with particular metal core have been shown to selectively adsorb explosive molecules (RDX, TNT) 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.
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
MEMS and Microcantilevers Significant work being done in ORNL and UC Berkeley • Thundat group on ORNL and Majumdar’s group in UCB •
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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.
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
PETN on Cantilevers
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Comparison of Explosives and Non-explosives
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Detection without Special Coatings •
Pinnaduwage and colleagues detected TNT deposited on a pulse-heated piezoresistive microcantilever via deagration 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
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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) •
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Amplified Fluorescence Polymers
Adv. Polym. Sci. 2005, 177, 151. S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Nomadic: Vapor detection of TNT Nomadics developed Fido, the only successful TNT sniffer.
DARPA Dog’s Nose program Objective: Match Canine Landmine Detection Performance Swager/MIT: Chemical Technology Nomadics: Instrumentation, Operations and Systems Development
http://www.chemicalagentdetection.com/presentations/paul.pdf
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Fluorescence Quenching sensitivity with TNT
0.2 0.18
ADI ADB
0.16 0.14
DI/I
0.12 0.1 0.08
DB
0.06 0.04 0.02
0 0
100
200
300
400
500
600
700
Concentration
Fluorescence quenching as a function of concentration for three molecules (DB, ADI, ADB) developed at IIT Bombay (courtesy Prof. Anil Kumar) The sensitivity of ADI and ADB is observed to be almost the same. S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Explosive Detection based on Fluorescence Quenching (from Prof. Anil Kumar) WHITE LIGHT
Polymer on silica gel without TNT
Polymer on silica gel with TNT
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Explosive Detection based on Fluorescence Quenching (from Prof. Anil Kumar) UV LIGHT (354 nm)
Polymer on silica gel without TNT
Polymer on silica gel with TNT
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Setup for Detection using Quenching Polymers (from Prof. Anil Kumar)
Pump
Power supply unit Photodiode Valve Glass Rod
Damper
Sample
Fluorescent Polymer Coating
Photodetector
24.5 mv
Multimeter
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Device Response to TNT Vapors ((from Prof. Anil Kumar) 6
5
Fluorescence signal (volts)
Fluorescence signal (volts)
6
Exposure to TNT
4 3 2 1
0
0
100
200
300
400
500
600
700
Response of an uncoated tube 5 4 3
2 1 0
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Time (sec)
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
50
100
Time (sec)
150
200
Polymer Microcantilevers with optical transduction Design and fabrication of SU-8 cantilevers Fabrication method
Flip-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 S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
The Portable Instrument
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Results using Microcantilever
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Micro – Cantilevers •
•
•
Cantilever Sensors o ~ 200um in size o Piezo-Resistive with electrical readout o In-house fabrication Material Science o Polymer Cantilevers with low stiffness, very high sensitivity for gaseous phase o Silicon Cantilevers stable in liquid medium Fabrication Technologies o Optical Lithography o Chemical Vapor Deposition o Spintronics, Chemical / Plasma Etching •
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Cantilever Functionalization o 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 interaction and thereby produced surface stress o Leads to change in resistance of piezoresistive layer o Analyte traces detected through highly sensitive dR/R instrumentation circuits
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Explosive Detection •
Polymer Micro – Cantilever and MEMS based Handheld Explosive Detectors with very high sensitivity
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Trace Detection of Explosive Molecules o o o
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Detection up to parts per billion molecules in air All derivatives of RDX, TNT and PETN Lab tested with up to 21 different explosive compounds
Low Cost Deployment o
Highly cost effective for mass deployment in Airports, Railway and Bus Stations, Hotels, Malls, Public Places
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Real Time Detection – Response in 5 to 10 seconds
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Fast boot up time, plug and play operation for cantilever sensor replacement S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Third Party Testing
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Detection using deflagration •
Deflagration Reaction o
o
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Convective burning of energetic material with a large surface area. 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. •
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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
o o o
Constructing thin membranes of materials having low thermal conductivity Use of suspension beams with high length-to-width ratio Decreasing the heated area Choosing a large pit depth of the suspended membrane S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Microheater and Sensor Design •
Silicon Dioxide platform o
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Heater o
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Area 330 micron x 330 micron. Thickness 500 nm Line width 30 micron. Total length 1.01mm
RTD o
Line Width 30 micron. Length 281 micron
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Fabricated Microheaters
Fabricated Interdigitated Microheater (New Design) S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Protocol •
RDX dissolved in Acetone and drop coated on heater.
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Different concentrations of RDX solution was used (5mg/ml and subsequently halved till 0.15625 mg/ml)
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About 1.8 microlitre drop size.
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Amount of RDX deposited on heater calculated for each concentration.
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At the lowest concentration it was 5ng on the active area.
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RDX vapor generator was also used for 1 set of experiments. 1 ppm vapor for 1 hour.
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Experimental Results
After Deflagration Active Area cleared of RDX
Before Deflagration Active Area covered with RDX
After Deflagration Active Area cleared of RDX
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Results (Output on Pulse) Heat liberated due to deflagration. • Increase in resistance more than due to applied voltage. •
Expanded output S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Results (Contd.. )
Output spike for concentration of 0.3125mg/ml
Output spike for concentration of 0.15625mg/ml
Vapor Phase output (1300C, approx 1ppm) S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Testing of Microheater for Repeatability
The differential signal of the two pulses with a concentration of 0.039mg/ml S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Instrumentation for Heaters
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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 •
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Optical system design Declad fiber exposing core
Layer of GNP on which receptors are bound
1
1 2 3 4 5 6, 7 stage 8 9 10
2
3
4
5
6, 7
8,
9, 10
Spectrometer
Optical source, (200 – 870 nm) Lens in a multi axis lens positioner and lens holder Microscopic objective lens connected to fiber coupler Multimode fiber coupler with tilt stage Fiber holder and chucks and holder Flow system with capillary tube of diameter 2 mm and support Fiber optic positioner Multi axis lens positioner Lens with screw for fiber optic probe mounting S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Real time detection of Explosive vapors
Response to TNT vapors: 4-MBA functionalized probe
Response to RDX vapors: 4-MBA functionalized probe
L-Cysteine modified probes S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
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. •
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
Acknowledgements Funding Agencies and PRMC Dr. Chidambaram (PSA to PM) Dr. Baldev Raj (Dir, IGCAR) Mr. Neeraj Sinha (PSA’s office)
Students
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)
Prasanth Sankar, Vibhor Khanna, A.V. Prasad, G. Suresh (Microheater) N. Kale, Ms. Seena V (Cantilevers) Jasmine (Quenching Polymers) Reshma Bharadwaj, Simon Feyles (LSPR) S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)
S. Mukherji, IIT-Bombay (mukherji@iitb.ac.in)