Sensors can be printed directly on human skin

Sensors are the eyes and ears of the electronics world. They gather data from multiple sources that can to be fed to the system’s electronic brain for processing. This desire for information has grown enormously since we entered the IoT era, and it is forecast there will be billions more sensors in operation in the near future. There’s always a desire to make these sensors smaller and less obtrusive, particularly when they will be worn on the body. Skin worn electronic sensors have the potential to change how we interact with the world. For example, we could continuously monitor our health.

Several methods have been employed to make small unobtrusive sensors for use on the human body, with mixed results. For example, flexible electronics don’t allow gas or moisture to pass through as they are normally printed on plastic films. However, advances in technology means we now have flexible electronics that are gas-permeable, but these still interfere with normal sensation. 3D printing has also been tried, but these devices are generally thicker and interfere with normal behaviour. Spinning electronic fibres has also been tried, but they don’t have a high degree of sensitivity or sophistication, and they’re difficult to transfer onto the object in question.

Now, a University of Cambridge led team has developed a new way of making high-performance bioelectronics that can be customised to a wide range of biological surfaces by printing them directly onto that surface. Their technique is partly inspired by spiders and their sophisticated and strong web structures adapted to their environment. The low-waste and low-emission way to make adaptive and eco-friendly sensors can be directly printed onto a wide range of biological surfaces. The sensors incorporate bioelectronics, so that different sensing capabilities can be added to the ‘web’.

“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 Professor 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.”

The ‘spider silk’ was spun from PEDOT:PSS (a biocompatible conducting polymer), hyaluronic acid and polyethylene oxide. The high-performance fibres were produced from water-based solution at room temperature, which allowed the researchers to control the ‘spinnability’ of the fibres. They then designed an orbital spinning approach to allow the fibres to morph to living surfaces, even down to microstructures such as fingerprints. Tests of the bioelectronic fibres, on surfaces including human fingers, showed that they provided high-quality sensor performance while remaining imperceptible to the host.

Most high-resolution sensors are made in an industrial cleanroom and require toxic chemicals in a multi-step and energy-intensive fabrication process. The Cambridge-developed sensors can be made anywhere and use a tiny fraction of the energy that regular sensors require. The bioelectronic fibres, which are repairable, can be simply washed away when they have reached the end of their useful lifetime, and generate less than a single milligram of waste.

The results are reported in the journal Nature Electronics.

https://www.cam.ac.uk/