Warwick OLFaction - WOLF Projects

WOLF E-Nose

As part of its activities, the Biomedical Sensors Laboratory is developing a new generation of electronic noses and gas analysers that combine both in-house and commercial gas sensor technologies. The WOLF electronic noses are the latest in this line of innovation. Importantly, as these systems are designed and built in-house, they offer a high degree of flexibility and can be tailored to meet the needs for specific applications. In addition to our in-house platforms, we have also developed a wide range of commercial systems. At present, there are four distinct series of E-noses, with selected examples shown below.

WOLF Series 1 Analyser

The series 1 analyser are small, portable units fitted with the latest in miniature gas sensors. Their purpose is geared towards environmental applications, and are therefore fitted with additional sensors to give an indication of the total air quality around the user. These sensors include light (including UV), sound, temperature, humidity, total volatile organic compounds (VOCs), toxic inorganic gases, and carbon dioxide. The units are battery powered, and can last up to three days on a full charge. The units communicate through an Android app to a mobile phone or portable tablet, to give a real time reading of the environment around the wearer.

The first generation unit was designed to be a similar size and shape to a smart watch. It included an integrated microcontroller, sensors and a Bluetooth BLE chip for communication with the user. An overview of the system is shown in the figure below:

The second-generation unit incorporated a carbon dioxide sensor along with an integrated microcontroller and Bluetooth module. Although slightly larger than the first version, it was designed to be worn on a belt or attached to a bag for convenient use in everyday settings. Like its predecessor, the device transmitted information to a mobile device, but it also recorded location data, enabling the creation of detailed maps of environmental quality. An example of this unit is shown in the figure below.

The third-generation Series 1 unit is currently under development. It will integrate a wider range of sensors and feature a convenient clip-on design, providing improved functionality for the wearer.

WOLF Series 2 Analyser

The Series 2 analysers are designed primarily for indoor and environmental monitoring applications. While they can operate on battery power, they are mainly intended for plug-in use, enabling long-term monitoring over periods of weeks or even months. Compared to the Series 1 units, they incorporate a broader range of sensors, including higher-specification devices and particle sensors that cannot be accommodated in the smaller Series 1 design.

These analysers have been deployed across a wide variety of environmental and agricultural applications. The first-generation Series 2 unit, shown in the photo below, features a robust metal enclosure and an OLED display to provide a real-time indication of sensor readings. Communication is enabled via a long-range wireless module, with an SD card included for situations where radio frequency communication is not possible. In addition, the system can be linked to a dedicated website, allowing online access to data from multiple deployed units.

The second-generation unit was built for use in rougher environments and equipped with protective rubber boots. It was developed specifically for transport applications, where the analyser can be placed inside a container or similar enclosure to monitor environmental conditions during transit. The device is battery powered, with a lifespan of several months on a single charge. An example of this unit is shown in the photo below:

WOLF Series 3 Analysers

The WOLF 3.1 and 3.2 analysers are compact, portable systems that can be taken on-site, while still being mains powered. The WOLF 3.1 features a gas chromatography (GC)–metal oxide detection system, in which pre-separation occurs in the GC column, followed by chemical analysis using an array of metal oxide sensors. It includes a fully integrated fluidic system, a touchscreen interface, and a real-time display for monitoring results, featured in the image below:

The WOLF 3.2 is currently under development and will use optical gas sensor technology to detect breath-based biomarkers of inflammation.

WOLF Series 4 Analyser

The WOLF Series 4 is a fully integrated electronic nose, featuring:

Desktop electronic nose design
Array of electrochemical and optical gas sensors
Fully integrated control and drive electronics
Environmental control hardware
Integrated flow control
Custom software interface developed in National Instruments LabVIEW
Intuitive graphical interface for ease of use
Data export to common software analysis platforms

This instrument is already being used in both medical and agricultural applications.

WOLF-AROMA

The field of olfaction remains one of the most underdeveloped technological areas in our modern digital world. While significant advances have been made in the ways we receive digital information through visual and auditory channels, olfaction still feels like a technology of the future. This is likely due to a combination of factors, including the dominance of other senses, limited training in olfactory perception, and a perception that smell is less important. Yet olfaction has the unique ability to enrich visual experiences and engage areas of the brain associated with long-term memory.

The potential applications for olfactory technology are wide-ranging, spanning medical, educational, and entertainment domains. For example, olfactory cues could help reduce anxiety and stress or support the diagnosis of degenerative disorders such as Parkinson’s disease. In museums or tourism environments, carefully designed scents can complement audio-visual displays to recreate historical experiences. Other applications include virtual reality and multimedia, enhancing gaming, television, and interactive entertainment.

Given these possibilities, it is surprising that olfactory displays are not yet commonplace. One major reason is the lack of simple, robust, digitally controlled olfactory technologies. Unlike traditional approaches such as air fresheners, perfumes, scented paper strips, or candles, these modern systems are designed to deliver a controlled range of olfactory experiences in a digital format.

There have been numerous attempts to create such digital olfactory displays. Early examples include the AromaRama cinemas of the 1960s, which released scents from auditorium seats, and Morton Heilig’s Sensorama, the first full VR system. Neither achieved commercial success, and olfactory experiences were largely limited to scratch-and-sniff cards until the late 1990s. Subsequent efforts have also faced challenges in achieving widespread adoption.

In response to the lack of commercially available technologies, our group has developed simple olfactory displays that can be easily constructed and adapted by other researchers. Two examples of these devices are shown below.

Liquid-Based Olfactory Display

Our group has previously developed and published two olfactory display units, both based on a thermal release mechanism. The first device used heated essential oils to generate a cloud of aroma, which was then dispersed by a small fan. The heating element consisted of platinum wire coiled inside a capillary tube and placed within a glass vial. The entire system was fully computer-controlled via a portable device, such as a tablet, using wireless communication. The unit could be loaded with up to eight different aromas, each of which could be used multiple times. The completed device was roughly the size of a Bluetooth speaker. A photo of the unit is shown below.

Wax-Based Olfactory Display

A more recent olfactory display uses Peltier heating elements and wax as the aroma carrier. The unit is fully computer-controlled and can hold up to 12 aroma capsules, each containing a distinct scent. These capsules can be activated individually or combined to create richer olfactory experiences. The device is larger than our original unit, roughly the size of a larger Bluetooth speaker. It was developed as part of a wine aroma game aimed at promoting sensory training. In testing, the portable device was evaluated with 15 volunteers to measure the detection and recognition times of six aromas associated with red and white wines. An overview of the unit is shown below.

The Future of WOLF AROMA

We are currently developing the next generation of olfactory displays, which will be showcased here once they are published. We are also exploring a wide range of applications for these devices.

For more information about our olfactory displays, please contact Prof James Covington.
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