The Bio-Sensor:
An
Effective Drugs and Explosives Detection System
K.E. O'Neil
Advanced
Aviation Technology Ltd.
Compton, Surrey, UK.
Abstract
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. |
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.
|
