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The Bio-Sensor:
An Effective Drugs and Explosives Detection System

K.E. O'Neil
Advanced Aviation Technology Ltd.
Compton, Surrey, UK.


A new tool is now available for the detection of drugs and explosives: the Bio-Sensor. The Bio-sensor is based on a simple but advanced technology. It is extremely sensitive, but easy to employ in a variety of operational environments. It is able to screen people, baggage, cargo, buildings, vehicles and aircraft. It is able to screen unambiguously for specific substances, chemicals or materials. It is able to do this during all the phases involved in the management of peoples and goods at airports: from entry into the passenger terminal through to the aircraft itself. The Bio-Sensor promises to radically improve the detection of drugs, explosives and other illicit and dangerous substances at airports. As such, it will greatly improve airport safety and security.

1. Introduction

The need to effectively screen passengers, baggage and cargo at airports for a wide range of illegal substances increases daily. These substances can threaten the safety, security and lives of everyone. They include: drugs, explosives, weapons, radio-active material, smuggled goods etc. A variety of agencies are involved and concerned with their detection, including customs, police, transport security, immigration, airlines, airport authorities, manufacturers and insurance companies. The legal and moral obligation to detect and prevent the movement of these substances through ports and airports, also grows with each passing day.

Traditional methods of screening people and baggage at airports have relied on a wide range of low and high tech solutions. The operational effectiveness of some of these methods and technologies is often random and can be less than reliable.

Figure 1: Archive picture of people and baggage at airport.

2. Existing Technologies

A variety of technologies and methods are available and routinely used for the screening and detection of illegal substances and materials. These include:

  • Imaging technologies
    (e.g. X-ray; gamma ray, Pulsed Fast Neutron)
  • Non-imaging technologies
    (e.g. Gamma backscatter, radio activity detectors, metal detectors, people detectors, dogs)
  • Chemical identification
    (e.g. Trace detectors, Nuclear Quadrupole Resonance (NQR), x-ray diffraction)

Each of these has specific characteristics and limitations. Aviation security typically applies a battery of solutions including most of the above to a greater or lesser degree. Baggage tends to receive more attention than cargo, despite the fact that most passenger aircraft carry cargo too.

3. Impact of Existing Methods

Despite the best efforts of the agencies involved, traditional screening methods also inhibit the flow of passengers, baggage and cargo. This, in turn, adds a high price to operations in terms of added costs, overheads, delays and lost business. Thus, there is a pressing need to make the screening process more reliable, effective, efficient and less intrusive.

In many countries only a few percent of suspect items are actually inspected. Yet, the total number of bags, freight items, vehicles and people entering airports and crossing borders every day is measured in millions. Freight is particularly difficult to screen effectively, due to the huge volumes and physical effort required. This means that, in practice, the actual detection rate of illegal substances by existing methods is relatively poor.

In short, current screening methods are costly, inefficient and often unreliable.

Figure 2: Archive picture of Airport Queue through Customs

4. The Bio-Sensor: How it Works

The Bio-Sensor is a new weapon for the detection of illicit substances. Although sophisticated, the process is relatively simple. It is an air sampling method, which is able to detect very low concentrations of a given substance.

The concept employs specially tailored antibodies which react with a given material or substance. The antibody is mounted on an extremely sensitive piezo-electric quartz microbalance system. In the presence of the substance, the antibody attaches itself to the target molecule leading to a weight reduction on the crystal which can be extremely accurately measured by the micro-balance system. The antibody is very specific - it reacts only with the substance in question and no other. The antibody is also very large in comparison with the airborne molecule, leading to a magnification effect.

4.1 The Bio-Sensor Process

The Bio-Sensor is essentially a three-step process: air sample collection, a concentration (or compression) phase and the detection and analysis phase.

Bio-Sensor System

Figure 3. System Diagram

4.2 Collection System

Most air sampling systems rely on the absorption of the airborne molecules, which means that detecting low concentrations of a substance can be problematic and subject to error (in both detection and measurement of concentrations).

The Bio-Sensor overcomes the problems of detecting low concentrations with a very effective sampling technique. For example, the Bio-Sensor technology was originally developed for detecting TNT in Land-mine clearance. Land-mines are notoriously difficult to detect and clear. It is especially difficult to reliably sample air for small concentrations of TNT in the open air. Yet Land-mine detection also requires close to 100% accuracy.

The Bio-Sensor's collection system is able to concentrate 100 litres of air into 10 micro-litres of solution of TNT. This is a concentration of gaseous molecules of TNT into a liquid solution by a factor of over a million to one. The Bio-Sensor also allows for cleaning of the system, whilst new samples are being collected, without risk of cross contamination. The use of an adsorption filter combined with a cooling trap, prevents dust and particles from entering the sensor unit.


Figure 4: Sensor Diagram

4.3 Measuring Concentrations of Substances

The antibodies are attached to the surface of a piezo-electric crystal. The quartz crystal oscillates at its natural frequency. Changing the mass of the crystal changes this natural frequency, which can be accurately measured by simple electronic means. When the antibody attaches itself to the substance in question it leaves the surface of the piezo-electric crystal, reducing its mass. This increases the natural frequency of the crystal.

The mass of the TNT antibody is over 600 times the mass of a gaseous TNT molecule. This leads to a considerable multiplier effect - resulting in much higher sensitivity to substances than in conventional methods, which rely on absorption. Clearly, the loss of an antibody 600 times the mass of a TNT molecule is easier to measure than the gain in mass of one TNT molecule.

Disturbances to the system are also easily measured, so the risk of faulty operation is significantly reduced.

4.4 Sensitivity

By measuring overall weight loss, the sensor is able to measure concentrations down to 10-12, when combined with the concentration process and the multiplier effect (of mass loss) this leads to an overall sensitivity of a million times lower at 10-19. This is comparable to the sensitivity of the very best trained dogs, is very accurate, more reliable and is much less easy to confuse.

4.5 Performance Characteristics

Performance can be measured in four ways: yield, sensitivity, speed and memory effect. Existing air-sampling systems, typically achieve a yield of 5%. The Bio-Sensor has already achieved yields of over 15% and production systems are expected to achieve 50%. This is a major advance over all other air-sampling technologies. Up to 600 litres a minute can be collected allowing detection over large volumes. The time to purge the system is 36 seconds. The reaction time between the antibody and the target substance is less than one second.

With current improvements to the injection system and to the mechanical and hydraulic design of the cell, it is projected to reduce the biosensor response time to 3 minutes. With further development this time can be reduced to 30 seconds or less. Thus, with the collection of 100 litres of air, the total process and analysis time would be approximately 1 minute. The collection system is self-cleaning and there is no memory effect.

4.6 Analysis and Software Processing

No sophisticated signal processing is required for sample analysis. Thus software costs and maintenance are kept to an absolute minimum. This also removes the risk of faulty software in the analytical phase. This is a key factor in reliability and in reducing through-life costs.

5. The Bio-Sensor in Operating Environments

The Bio-Sensor is able to screen large areas either for a range of substances or for a specific substance. The Bio-Sensor's sensitivity and accuracy is such that it is able to identify WHEN a more detailed search is required. The same technology can then be used to carry out a closer search with consequent greater efficiency, effectiveness and reliability. The safety of the Bio-Sensor has been extensively demonstrated during mine clearing operations, where it has been shown to be able to detect the presence of mines with great reliability and to rapidly declare large areas as safe i.e. when the Bio-Sensor indicates that no mines are present.

The Bio-Sensor is more sensitive and reliable than dogs in detecting illicit substances such as drugs and much less easy to confuse. It is also more cost effective. The Bio-Sensor can be fixed or portable and can efficiently screen people, baggage, cargo, lorries, buildings or even whole aircraft. (Place Portable Sensor Picture here) Thus the Bio-Sensor is able to remove the "hit and miss" nature of the screening process, replacing it with an efficient, effective and reliable operating method. This helps to increase the effectiveness of other screening technologies, so safeguarding existing airport safety and security screening investments (i.e. enabling those methods to be deployed in a properly effective manner according to their inherent capabilities).

6. Bio-Sensor Developments

Most Substances can be detected if the appropriate antibody has been developed for it, including chemical and biological agents. Currently, a sensor for amphetamine has been fully developed and sensors for cocaine, heroin and cannabis are in the final stages of development with delivery and volume production during the year 2000. Sensors for other drugs will also be made - according to market demand. Sensors have also been developed for explosives such as TNT. Antibodies and antigenes for the explosives RDX and PETN are currently being developed along with their sensors and these are also expected to be available during the year 2000.

7. Key Characteristics

The system is able to detect specific substances, chemicals, biological agents or other materials. This includes drugs and explosives. The system that is used to collect and concentrate the target substance is very effective. Thus the system has several key characteristics, which makes it very efficient and reliable in detecting illicit substances:

  • It is unambiguous and is able to identify specific substances.
  • It is able to detect very low concentrations as required.
  • It can sample over a large volume or in small areas.
  • It is very accurate.

The use of antibodies in the sensor makes the system very difficult to cheat or confuse. Consequently, the Bio-Sensor is set to become a major tool in the improvement of Airport safety and security.

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Advanced Aviation Technology Ltd.
The Old Post Office,
The Street, Compton,
Surrey GU3 1ED. ENGLAND.
Tel. +44 1483 811 311.

Email: kim.oneil@aatl.net

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