Incredible new eco-friendly sensors inspired by spider silk and 50 times smaller than a human hair could be used in fields from healthcare monitoring to virtual reality.
The sensors, developed by University of Cambridge researchers, can be printed on a range of biological surfaces from a finger to a flower petal.
They are so lightweight that they even printed them directly onto the fluffy seedhead of a dandelion without collapsing its structure.
And when printed on human skin, the fibre sensors conform to the skin and expose the sweat pores, so the wearer does not detect their presence.
Tests of the fibres printed onto a human finger suggest they could be used as continuous health monitors, as an alternative to more obtrusive wearables with built-in sensors like smartwatches.
“If you want to accurately sense anything on a biological surface like skin or a leaf, the interface between the device and the surface is vital,” said Prof Yan Yan Shery Huang from Cambridge’s Department of Engineering, who led the research.
“We also want bioelectronics that are completely imperceptible to the user, so they don’t in any way interfere with how the user interacts with the world, and we want them to be sustainable and low waste.”
Augmenting human skin with electronic sensors could change how we interact with the world around us. Printing them directly onto the skin could also be used for understanding skin sensations or improve the sensation of ‘reality’ in gaming or virtual reality applications.
Most methods devised so far for making wearable sensors have drawbacks.
Using flexible electronics would be like wrapping skin in cling film, as these are normally printed on plastic films that do not allow gas or moisture to pass through.
And while other researchers have recently developed flexible electronics that are gas-permeable, like artificial skins, they still interfere with normal sensation and rely on energy- and waste-intensive manufacturing techniques.
3D printing of bioelectronics is less wasteful but creates thicker devices that can interfere with normal behaviour.
And while spinning electronic fibres results in devices imperceptible to the user, they do not have great sensitivity or sophistication and are difficult to transfer onto the object in question.
The Cambridge team spun their bioelectronic ‘spider silk’ from PEDOT:PSS - a biocompatible conducting polymer - with hyaluronic acid and polyethylene oxide.
These high-performance fibres were produced from water-based solution at room temperature, which enabled the researchers to control the ‘spinnability’ of the fibres.
They designed an orbital spinning approach to allow the fibres to morph to living surfaces, even down to microstructures such as fingerprints.
“Our spinning approach allows the bioelectronic fibres to follow the anatomy of different shapes, at both the micro and macro scale, without the need for any image recognition,” said Andy Wang, the first author of the paper. “It opens up a whole different angle in terms of how sustainable electronics and sensors can be made. It’s a much easier way to produce large area sensors.”
Another advantage of them is that they can be made anywhere and use a fraction of the energy that regular sensors require. By contrast, most high-resolution sensors are made in an industrial cleanroom and require the use of toxic chemicals in fabrication process that used multiple steps and lots of energy.
The new bioelectronic fibres are repairable and can be washed away when they have reached the end of their useful lifetime. They generate less than a single milligram of waste. By comparison, a typical single load of laundry produces between 600 and 1,500 milligrams of fibre waste.
“Using our simple fabrication technique, we can put sensors almost anywhere and repair them where and when they need it, without needing a big printing machine or a centralised manufacturing facility,” said Prof Huang. “These sensors can be made on-demand, right where they’re needed, and produce minimal waste and emissions.”
Precision agriculture and environmental monitoring are other fields the sensors could be used in and in future other functional materials could be incorporated into this fibre printing method to build integrated fibre sensors for augmenting the living systems with display, computation, and energy conversion functions.
The research, published in the journal Nature Electronics, is being commercialised with the support of Cambridge Enterprise, the university’s commercialisation arm.
The research was supported in part by the European Research Council, Wellcome, the Royal Society, and the Biotechnology and Biological Sciences Research Council (BBSRC), part of UK Research and Innovation (UKRI).
