HAND-HELD EXPLOSIVES SENSOR SYSTEM

by

Charles D. Bosco

Senior Research Engineer

Systems Management and Production Center

University of Alabama

Huntsville, Alabama

Prepared by

UTCA

University Transportation Center for Alabama

The University of Alabama, The University of Alabama in Birmingham,

and the University of Alabama at Huntsville

UTCA Report Number 03306

August 1, 2003

Technical Report Documentation Page

1. Report No FHWA/CA/OR-		2. Government Accession No.		3. Recipient Catalog No.
4. Title and Subtitle Hand-Held Explosives Sensor System			5. Report Date August 1, 2002
			6. Performing Organization Code
7. Author Charles D. Bosco			8. Performing Organization Report No. UTCA Final Report
9. Performing Organization Name and Address Systems Management and Production Center University of Alabama Huntsville, AL 35899			10. Work Unit No.
			11. Contract or Grant No. UTCA Identification Number - 03306
12. Sponsoring Agency Name and Address University Transportation Center for Alabama P O Box 870205 University of Alabama Tuscaloosa, AL 35487-0205			13. Type of Report and Period Covered Final Report
			14. Sponsoring Agency Code
16. Abstract One of the most important problems facing the U.S. Department of Transportation is the detection of illegal chemicals and explosives entering this country. There are various government agencies performing detection by means of physical inspections, sophisticated detection instrumentation and trained “sniffing” dogs. All of these methods have their limitations, especially costs. The purpose of this investigation was to study the feasibility of integrating a variety of microcantilever sensors into a hand-held sensor system capable of sensing and identifying illegal explosives. Researchers at the University of Alabama at Huntsville have developed the capability to design, fabricate and test microcantilever devices that can detect trace amounts of most organic and inorganic chemicals. These sensors are so sensitive that, in some cases, they can exceed the sensitivity of trained dogs. The sensors are small enough that many sensors can be placed on a single silicon chip. An extensive literature search was performed to determine the U.S. Department of Transportation’s challenges in detecting contraband explosives. This included a technical evaluation of present-day detection instrumentation and the capabilities of sniffing dogs. It was followed by a detailed study of microcantilever technology and its application to explosives detection. To determine the latest state-of-the-art, interviews were conducted with a customs inspector, a sniffing dog handler, and the head of a microcantilever laboratory. Other sensor technology was investigated to ensure that microcantilevers are indeed the most appropriate for explosives detection. The investigation concluded with a prototype design of a multi-sensor system, and a cost analysis of fabricating such a system.
17. Key Words Chemical sensors, microcantilever, explosives, homeland security			18. Distribution Statement
19. Security Class (report) Unclassified	20. Security Class. (Of this page) Unclassified		21. No of Pages		22. Price

Contents

Contents ……………………………………………………………………………. i

List of Tables ………………………………………………………………………. v

List of Figures ……………………………………………………………………… v

Executive Summary ………………………………………………………………… vi

1.0 Project Objective …..………………………………………………………..…... 1

2.0 Background ……………..………………………………………………….…… 2

Introduction ………………………………………………………………………. 2

Transportation Inspection Problems ……………….……………………………. 2

Methods of Detection …………………………….………………………………. 4

Detection Instrumentation ………………..…….………………………….….. 4

Sniffing Dogs ……………………….………….……………………………… 4

New Technology …………….…...…………………….………………………. 5

Local Need for Explosives Detectors ……………….…………………….…… 6

Inspection at Different Locations ………………………..……………………….. 6

Inspecting Ships Before Entering a Port ……………………………..………… 6

Inspecting at Ports …………………………………………..…………….…… 7

Inspecting Borders ……………………………………………………….……. 8

Inspecting at Airports …………………………………………………………. 8

Inspecting Railroads and Trucking ……………………….…………………… 9

3.0 Explosives …………..…………………………………………………………… 10

Introduction …………………………………………………………….………… 10

Taggants ………………………………………………………………………..… 12

4.0 Detection Instrumentation ……………………………………………………… 14

5.0 SniffingDogs …………………………………………………………………… 18

Capability of Sniffing Dogs ……………………………………………….…….. 18

Accuracy ……………………………………………………………………… 18

Sensitivity ……………………………………………………………….……. 19

Comparison With Instrumentation ……………………………………………. 20

Volatility Problems ……………………………………………………………… 21

Limitations of Sniffing Dogs…………………………………………….………. 22

Comparison of Sniffing Dogs to Sensing Instrumentation ………………………. 23

Army Working Dogs …………………………………………………………….. 25

6.0 Current Instrumentation ………………………………………………………… 27

7.0 Microcantilever Technology ………………………………………………….… 30

Introduction ………………………………………………………………………. 31

Background Technology …………………………………………………………. 32

Sensor Detection Methods ……………………………………………………….. 33

Physical Properties ……………………………………………………..………… 33

Microcantilever Sensitivity ………………………………………………….…… 34

Sensitivity Analysis…………………………………………………. ………… 34

Comparison to Existing State-of-the-Art Techniques …………………………. 35

Detection of Explosives ………………………………………………………...… 37

Advantages of Microcantilevers over Conventional Sensors ………………..…… 38

Comparison of Microcantilever Sensors to Sniffing Dogs …………………..……. 38

Accuracy and Stability ……………………………………………………….……. 40

University of Alabama Nanometer/Micrometer Fabrication Facility ……………... 40

8.0 Prototype of Explosives Sensor Design ……………………………………..…… 43

Introduction ……………………………………………………………………..…. 43

Developing the Sensors …………………………………………………………….. 43

Designing the Electronics ………………………………………………….……… 44

Designing the Software ……………………………………………………………. 44

Designing the Display ……………………………………………………………… 45

Designing the Power Supply …………………………………………………….…. 46

Designing the Package …………………………………………………………….. 46

Estimated Research and Development Effort……………………………… ……… 46

Sensor Development ………………………………………………….…………. 46

Electronics Development ………………………………………………………… 46

Software Development ………………………………………………………….. 46

Development of Package ………………………………………………………... 47

Estimate of Final Cost of Sensor System …………………………………….…. 47

9.0 Conclusions and Recommendations …………………………………………….... 48

10.0 References ……………………………………………………………..………… 50

List of Tables

Number Page

3-1 Chemical composition of commonly used explosives…………………………… 10

3-2 Common major chemicals found in explosives and explosive mixtures ……….. 11

5-1 General comparison between instrumentation

explosive detection devices and trained detector dogs ………………………. 23

7-1 Comparison of techniques for mercury analysis ………………………………… 35

7-2 Gravimetric sensitivity of oscillating acoustic wave devices…………………… 36

List of Figures

Number Page

5-1 Canine olfactory sensitivity functions…………………………………………. 20

7-1 Different micrometer response modes ………………………………………… 33

Executive Summary

One of the most important problems facing the U.S. Department of Transportation is the detection of illegal chemicals and explosives entering this country. There are various government agencies performing detection by means of physical inspections, sophisticated detection instrumentation and trained “sniffing” dogs. The use of inspectors is expensive due to the limited number and the cost of personnel. Instrumentation is very useful, but the more sensitive instruments are very expensive, and therefore, are purchased in limited numbers. Sniffing dogs provide a very good compromise. The handlers provide the human evaluation and decision making while the dogs are very good at detecting trace odors of explosives, drugs, and currency. The problems associated with dogs are that a trained dog is expensive and requires a skilled handler and upkeep. Also, dogs cannot work long hours.

The purpose of this investigation was to study the feasibility of integrating a variety of microcantilever sensors into a hand-held sensor system capable of sensing and identifying illegal explosives. Researchers at the University of Alabama at Huntsville have developed the capability to design, fabricate and test microcantilever devices that can detect trace amounts of most organic and inorganic chemicals. These sensors are so sensitive that, in some cases, they can exceed the sensitivity of trained dogs. Also, hundreds of these sensors can be placed on a chip the size of a computer chip.

An extensive literature search was performed to determine the U.S. Department of Transportation’s challenges in detecting contraband explosives. This included a technical evaluation of present-day detection instrumentation and the capabilities of sniffing dogs. It was followed by a detailed study of microcantilever technology and its application to explosives detection. To determine the latest state-of-the-art, interviews were conducted with a customs inspector, a sniffing dog handler, and the head of a microcantilever laboratory. Other sensor technology was investigated to ensure that microcantilevers are indeed the most appropriate for explosives detection.

The investigation concluded with a prototype design of a multi-sensor system, and a cost analysis of fabricating such a system.

Section 1.0

Project Objective

One of the most important new scientific accomplishments to emerge recently from sensor research has been the development of microcantilever sensors. This sensor has been demonstrated to have such extreme sensitivity that specialized sensor systems using this technology have the potential to equal or exceed the detection capabilities of sniffing dogs and some of the more sensitive laboratory measuring equipment. The object of this investigation was to determine the feasibility of integrating a variety of microcantilever sensor devices in a hand-held sensor system capable of sensing and identifying trace amounts of explosives. Trained dogs and some specialized portable instrumentation traditionally do this work very well, however, the new microcantilever technology has the potential of replacing sniffing dogs and reducing the size and cost of portable instrumentation. A sensor system based on this technology could enjoy widespread use for U.S. Department of Transportation (USDOT) inspectors.

As part of this investigation, an analysis was made of the projected cost of a hand-held sensor, assuming that one could be built to match or exceed the effectiveness of dogs.

The approach to this investigation was to accomplish the following tasks:

1. Study the USDOT’s challenges in identifying contraband containing explosives.

2. Study the present technology used to detect explosives and determine its effectiveness, ease of use, cost, and upkeep.

3. Evaluate the capability of sniffing dogs to detect explosives.

4. Evaluate microcantilever technology.

5. Determine whether a cost-affordable multi-sensor system can be designed and fabricated.

Section 2.0

Background

Introduction

The focus of this investigation is to support the U.S. Department of Transportation in its quest for new technology to improve the detection of contraband explosives. Consequently, it will be useful to briefly describe the problems encountered by USDOT inspectors.

The Department of Transportation is faced with the overwhelming task of preventing the transportation of illegal explosives into and throughout the United States. Since the tragic twin towers attack, the threat level has increased significantly. Recently, the government has formed the Homeland Defense Department to consolidate the many agencies that are responsible for protecting this country. At this writing, it is unclear as to how the new organization will operate.

Contraband consists of many things, including drugs and currency, however this investigation will only be concerned with the detection of explosives or chemicals used in explosives.

Currently, inspections are done using inspectors, detection instrumentation, and sniffing dogs. Each has its strong and weak points, but whenever additional personnel are hired, the expenses increase significantly. Sniffing dogs have been found to be very useful, but they can only detect explosives that are not well sealed. They have other limitations that will be discussed later. Large sophisticated x-ray and other inspection machines are very important in identifying well-sealed explosives embedded in cargo or luggage. These instruments are usually very expensive and even the portable versions are too expensive for wide distribution. These instruments also have their limitations, and which will be discussed later.

Transportation Inspection Problems

Because of the vast size of the United States, i.e., borders with two large countries, and two major seacoasts (not including the Gulf of Mexico and the Great Lakes), the job of government inspectors is daunting. This task became significantly more important after the attack on the New York twin towers in 2001. While the USDOT is increasing the number of inspectors and improving techniques, the cost and size of such an operation is overwhelming. Also, there is the problem of coordination with other agencies such as the Department of Commerce, Customs, etc. The new Homeland Defense Department will attempt to provide a uniform approach to inspections and to the identification of contraband.

One of the more recent attempts to address the problem was to increase the number of inspectors. At the time of this investigation the airports were hiring 50,000 new federal screeners to check passengers. However, only the tiniest percentage of containers, ships, trucks, and trains that enter the United States each day are subject to examination. Therefore, a weapon of mass destruction could be hidden among this cargo. Should the maritime or surface elements of America’s global transportation system be used as a weapon-delivery device, the response would almost certainly be to shut the system down at an enormous cost to the economies of the United States and its trade partners. (Gary Hart and Warren B. Rudman, 2002)

Because of the costs and the number of inspectors needed, it is impossible to inspect all cargo before it enters the country, when it enters the country, and as it travels throughout the country. Even if it were possible, the delays in delivery would be intolerable. Therefore, an efficient process must be established whereby the USDOT can have a reasonable level of confidence that contraband has not passed through the inspection system. There are major obstacles to this process:

a. High cost of employing a large number of inspectors.

b. High cost of purchasing and maintaining sophisticated inspection equipment.

c. Long delays in delivery due to involved inspection techniques

d. Delays due to false positive signals from measuring equipment

Added to the above problems are the costs associated with training inspectors in the use of the new measuring equipment, and in the case of sniffing dogs, the cost of purchasing and maintaining them. The benefits and disadvantages of using sniffing dogs will be discussed in a later section.

As can be seen from the above, the major obstacle is cost. As in all finances, costs are managed in two ways, i.e., the elimination of waste or the increase in revenue. Elimination of waste is always desired, but because of the seriousness and scope of the problem, we can expect revenues to increase. The American public realizes that there are going to be significant costs associated with the protection of this country. However, even with large increases in funding, the problems will not be solved. While every single piece of cargo entering the country could theoretically be inspected, all trade would essentially stop. Given all this, then what is the answer?

The answer is to increase funding significantly for new technology to develop small, portable, non-intrusive, sensitive, low-cost inspection instrumentation. This would be a major undertaking, but the benefits would be worth it. It would allow effective inspections without significantly affecting the free flow of commerce.

There are over 40 departments of the United States government responsible for border inspections. However, no one agency searches specifically for explosives. (Conversation with a representative of Customs Service, 2003) The creation of the new Homeland Defense Department will attempt to bring these agencies together. In a memorandum concerning domestic preparedness, prior to the formation of the Department of Homeland Defense, Director Tom Ridge said the following. “It [the Department of Homeland Security] would assume responsibility for operational assets of the Coast Guard, Customs Service, Immigration and Naturalization Service and Border Patrol, the Animal and Plant Health Inspection Service of the Department of Agriculture, and the recently created Transportation Security Administration - allowing a single government entity to manage entry into the United States.” (Memorandum, Homeland Security 2001)

Methods of Detection

Aside from physical inspection by government agents, inspections are done using fixed instrumentation, portable instrumentation, and sniffing dogs. Depending on the particular situation, one or more of these techniques are used. When possible, a pre-screening analysis is used to determine cargo more likely to contain contraband.