Yorkshire firm Peratech is developing a sensor for volatile organic compounds (VOCs) based on its proprietary touch-sensing material QTC.
VOCs are sometimes hazardous or flammable chemicals that are used in paint and industrial processes, and VOC vapours, which are mists of tiny droplets, are also used to deliver other chemicals.
The company's QTC (quantum tunnelling composite) material fundamentally consists of conductive particles buried in a non-conductive flexible support medium.
The mixture is designed so that electrons will tunnel between the particles if a potential is applied, said the firm. When the material is deformed, the distance between conductive particles changes, which causes a change in electron flow, giving it a predictable force/resistance characteristic.
So far the firm has licenced the technology for touch sensing to Samsung for a five-way navigation switch, and to touch screen firm Nissha.
QTC is a material that senses force, not just pressure, it can detect different types of force including shear, twisting and swelling.
It is the material's ability to detect swelling that has been exploited in the detector for VOCs.
"The sensor is something that we developed with the University of Durham and have never really commercialised," Philip Taysom, joint CEO of Peratech, told Electronics Weekly.
QTCs can be made in two forms: bulk elastomer and printable ink emulsions.
"The bulk material can be made with a lot of different elastomers. We use silicones tuned to swell in the presence of VOCs for the sensor," explained Taysom.
To increase surface area, the bulk VOC sensing material is ground into small granules.
"A granule smaller than a pin-head contains hundreds of thousands of QTC junctions," said Taysom. Packed together, "the granules have a high surface area and can absorb very much more quickly than traditional sensors, and reset very much more quickly."
According to Taysom, these traditional sensors use saturation absorption into a solid block and require concentrations of 100,000-200,000ppm to detect reliably, while his QTC version operates well with 10,000-20,000ppm.
"This is largely to do with the large surface area," said Taysom.
By suspending the granules in a particular liquid they can be applied to textiles where they dry into a functional cloth.
"We can make a VOC sensor which can be worn, or made into safety equipment, or built into ships or planes," said Taysom.
Back with the firm's traditional business of force sensing, he revealed that Peratech is in discussions with an automotive partner.
In this case, the partner is considering building QTC sensors into car seats to measure the position and weight of occupants as data for the airbag firing system.
Peratech's most recent commercial announcement was QTC Clear, which is being pitched against traditional resistive touch screens.
A layer 6-8µm thick is sandwiched between two layers of indium-tin oxide-coated glass or hard plastic in front of the screen where it allows the location of deflections as low as 1-2µm to be measured.
"Both resistive and capacitive touch screen technologies have their drawbacks," said Taysom at its launch.
"Resistive is not very accurate and can't do multi-touch well, so it is becoming less popular than capacitive, but the latter uses a lot of power, constraining it to smaller screen sizes.
"QTC Clear can be made in any size and provides multi-touch, sensitivity, accuracy, low power consumption and adds the third dimension of pressure."
Multi-touch capability is achieved by replacing the upper and lower ITO conductor sheets with an X-Y grid, and actuation force of a typical glass-fronted QTC touch screen would be "10g comfortably and 5g can be achieved, and up to 1kg", said Taysom.
By exploiting the material's predictable force-resistance curve, force can be added as a third dimension of screen touch, which is why Peratech is also marketing QTC at capacitive touch screen makers. "Capacitive touch screen manufacturers can augment with the addition of QTC Clear to provide additional features from the force sensitivity, such as touch activation of the capacitive matrix to save power, 3D menus, variable line widths, and more intuitive gaming interaction," said the firm.
"Very little alteration is needed to the control electronics in either case, except to take advantage of the new features."
Firms including Samsung and Nissa have licensed Peratech's opaque QTC material and are manufacturing products, and there is already one undisclosed licensee for the transparent version.
Before the introduction of Clear the firm has been licensing an opaque form of QTC - applied as a thin gasket around the edge of the display - to add a third dimension to touch screens.