Biomimetic Olfactory Chips: Are Artificial Intelligence and E-Noses the Next

The Difficulties Of Artificial Olfaction

While machine vision has made tremendous progress in the last few years, other artificial senses have lagged behind. One of them is the sense of olfaction or ‘smell’.

This is because we have long known how to get a precise electric signal in response to light, something that has been used on a massive scale since the first digital cameras. In contrast, smell is essentially the detection of volatile chemical substances.

This is a lot more difficult for a few reasons:

• Odorant chemicals are rarely “pure”. They are instead present in complex mixes that can complicate their detection.
• The threshold of detection needed to equal human or animal sense of smell is very low, detecting concentrations generally in the ppm range (part per million, or 0.0001%).
• Miniaturization is essential for most applications, requiring both advanced chips and low power consumption.
• Any detection based on a chemical reaction will require regular changes of the catalysts or chemicals used in the sensor.

For all these reasons, most chemical / olfactory digital detection is currently limited to a few chemical compounds. And generally only used in an industrial setting where the dangerous chemicals to be detected are expected to come from accidents or leaks, for example, carbon monoxide, ozone, chlorine, etc.

This could change thanks to the development of biomimetic olfactory chips by researchers on the team of Prof. Fan Zhiyong, Chair Professor at the Hong Kong University of Science and Technology (HKUST).

Source: HKUST

Biomimetic Olfactory Chips

How Does Smell Work?

The way the sense of smell works in animals & humans is through an array of “chemical detectors” called olfactory receptors, able to detect with high sensitivity a wide range of volatile chemicals.

The number of genes coding for such olfactory receptors can vary from 300 to 1,200 depending on the species and how important the sense of smell is for it.

So, instead of having one receptor for every possible chemical molecule, every compound will have a unique “footprint” produced when activating each of these receptors slightly differently. The olfactory bulbs then assemble this complex signal into a nerve signal and interpret it by a part of the brain called the olfactory complex.

Building An Olfactory Chips

HKUST researchers have created a way to replicate this system, bypassing the constraints of building a miniaturized receptor for each possible chemical compound.

They assembled nanotube sensor arrays on a nanoporous substrate, reaching up to 10,000 individually addressable gas sensors per chip.

This data is then processed by a neural network algorithm to be translated into a “perception” of a specific chemical digital smell.

Source: HKUST

Olfactory Chips Potential

This design gives the olfactory chips the potential to simultaneously detect both the presence and concentration of a dozen or more chemicals at once.

As a demonstration, the team created a biomimetic olfactory chip that demonstrated exceptional sensitivity to various gases, and with excellent distinguishability for mixed gases and 24 distinct odors.

They then integrated both the olfactory chip and vision sensors on a robot dog, creating a combined olfactory and visual system that can accurately identify objects in blind boxes, pretty much like a “real dog”.

Source: HKUST

Olfactory Chips Applications

Safety

The most immediate application of olfactory chips is where most chemical detectors are currently used: safety applications. This includes factories, water treatment stations, petrochemical industries, pipe leak detection, and environmental monitoring (air pollution, etc.).

These new types of detectors could detect more chemicals at once than previous technologies, allowing for a larger data stream and better assessment of safety.

Defense & Security

As demonstrated by the robodog prototype, such a detection system could be used to detect otherwise invisible threats. From drug smuggling to detection of explosives, every activity where sniffer dogs are used could be systematized, thanks to the merger of AI, autonomous robotics, and olfactory chips.

Search and rescue could also benefit from olfactory chips to find survivors under destroyed buildings after a natural catastrophe.

Food & Farming

One reason why most animals have a developed sense of smell is to detect if a food is edible or spoiled. We can imagine that very sensitive olfactory chips specialized in food products could be very useful for the food industry.

Similarly, farming drones could also be used to smell the ripening of fruit, the presence of fungal crop diseases, insect pheromones, etc.

Cancer and disease detection

It has been known for a while now that some diseases are associated with the emission of specific smells….