“Panchromos produced a robust and functional prototype for field trials in a cost-effective manner”
Honeybees have a very acute sense of smell, are quick to train, inexpensive to keep and do not take up a lot of space. They can detect extremely low concentrations of volatile compounds—parts per trillion for some chemicals—with very high specificity. This makes them ideal sensors to detect trace vapours, with applications ranging from screening for explosives and drugs to medical diagnostics. Bees naturally exhibit a Proboscis Extension Reflex (PER) when they are presented with food, and can be conditioned to show a PER when confronted with other very specific stimuli. This behaviour is the basis of Inscentinel’s VASOR technology (short for Volatile Analysis by Specific Odour Recognition).
When we got involved Inscentinel had already built a first proof-of-concept prototype that used a camera and image analysis software running on a PC to detect the PER from the 3 bees that the unit contained. Our brief was to turn this concept into a self-contained hand-held device with 36 bees suitable for practical field trials. This meant we could not use cameras or PCs. It also meant the unit would need to supply its own clean filtered air, would need to be battery powered, small and light.
Bees in a box
First of all, I have to say that the bees are not harmed in any way: After their sniffer duty they are returned to the hive to live out the rest of their lives. As can be seen in the image above the bees are gently restrained in holders to enable us to detect a PER by the partial obscuration of an infrared beam – the bee in the picture has its proboscis extended between the infrared LED in the foreground and the photodetector mounted behind the horizontal aperture in the bee holder. Apart from the detector each beeholder also contains a heater to keep the bee warm in cold weather, and a microcontroller chip giving complete traceability. Inscentinel was awarded 3 patents on the beeholder.
A crucial part of the VASOR principle is that there needs to be a stepwise change in odour concentration to elicit a PER – slow changes will not be detected. That meant we had to come up with an airflow system that could switch between unfiltered and filtered air, without changing the flow rate as that could also serve as a trigger for a PER.
We designed and built the VASOR 136 product demonstrator as seen on the right image above, and this unit was used for a number of field trials for a security application. Overall results have been very positive, with the VASOR detecting trace vapours of explosive materials where a commercial hand-held device currently used in airports didn’t.