Transparent fibre sensors 'smell, hear and touch'

The transparent conducting fibres are 100 times thinner than a human hair and could be applied to health monitoring, Internet of Things devices and biosensing.

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The fibre printing technique, reported in Science Advances, can be used to make non-contact, wearable, portable respiratory sensors. According to Cambridge University, these printed sensors are high-sensitivity, low-cost and can be attached to a mobile phone to collect breath pattern information, sound and images simultaneously.

First author Andy Wang, a PhD student from Cambridge's Department of Engineering, used the fibre sensor to test the amount of breath moisture leaked through his face covering, for respiratory conditions such as normal breathing, rapid breathing, and simulated coughing. The fibre sensors are said to have significantly outperformed comparable commercial sensors, particularly in monitoring rapid breathing, which replicates shortness of breath.

The fibre sensor has not been designed to detect viral particles - scientific evidence increasingly points to viral particles such as coronavirus being transmitted through respiratory droplets and aerosols – but measuring the amount and direction of breath moisture that leaks through face coverings could act an indicator of 'weak' points in the protection.

The team found that most leakage from fabric or surgical masks comes from the front, especially during coughing, while most leakage from N95 masks comes from the top and sides with tight fittings. Nonetheless, both types of face masks, when worn properly, help to weaken the flow of exhaled breath.

"Sensors made from small conducting fibres are especially useful for volumetric sensing of fluid and gas in 3D, compared to conventional thin film techniques, but so far, it has been challenging to print and incorporate them into devices, and to manufacture them at scale," said Dr Yan Yan Shery Huang from Cambridge's Department of Engineering, who led the research.

Huang and her colleagues 3D printed the composite fibres, which are made from silver and/or semiconducting polymers. This fibre printing technique creates a core-shell fibre structure, with a high-purity conducting fibre core wrapped by a thin protective polymer sheath.

In addition to the respiratory sensors, the printing technique can also be used to make biocompatible fibres of a similar dimension to biological cells, which enables them to guide cell movements and 'feel' this dynamic process as electrical signals.

"Our fibre sensors are lightweight, cheap, small and easy to use, so they could potentially be turned into home-test devices to allow the general public to perform self-administered tests to get information about their environments," Huang said in a statement.

The team is to develop this fibre printing technique for a number of multi-functional sensors, which could potentially detect more breath species for mobile health monitoring, or for bio-machine interface applications.