Innovation

'Soft sensors' are about to make the human body more online than ever

Get ready for another stream of data heading for the cloud.

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Your phone knows how many steps you’ve walked and your Fitbit knows your current heart rate. But are you ready for even more streams of data to hit your digital life, collected through a stream of new “soft sensors” that resemble a stress ball?

A team from Imperial College London announced Tuesday that they had made a breakthrough in the quest to create force-sensitive sensors in stretchy and squeezy form factors. The findings were published in the journal ACS Applied Materials & Interfaces.

It may seem like a means to create a cool squeezy ball, but the breakthrough represents a new method of collecting vital health data. One such application could involve giving a hand injury patient a squeeze ball and making them squeeze, helping them measure the pressure and understanding how they’re progressing. Another application could include a leg band for use in exercise, and a chest band for monitoring breathing.

“We hope this method will allow us to make low-cost soft sensors that are reliable and portable, that can be used to monitor people’s health in their own homes,” Michael Kasimatis, from the university’s department of bioengineering, said in a statement. “Such sensors could be coupled with a mobile device, such as a smartphone, so that the data they generate can be easily processed and stored on the cloud, which is important for applications in digital healthcare.”

Imperial College London's sensor in action.Imperial College London

It’s the sort of quantified health data gradually being collected by smartphones, and it’s shown to have big benefits in recovery. The Apple Watch Series 4, for example, offers an electrocardiogram for measuring heartbeats and flagging up irregularities. The feature saved one Virginia man in December 2018 from a silent heart issue. An August 2018 patent has suggested future wearables could expand this further by measuring glucose levels for diabetics.

In this case, the squishy sensors are potentially measuring forces and pressures that were previously difficult to quantify.

The main difficulty until now has been developing a means of connecting the soft material to the electronic components inside the creation. Earlier efforts involved using adhesives or metal clamps, but the adhesives would gradually come loose and the clamps would tear the material. This has stopped a number of such sensors from making it to market.

The breakthrough is in using tiny bits of metal-coated silicon. This is used to encourage a chemical bond between the rubber and the components. The contacts are smooth on one side to connect with the rubber, while the other side is plated with copper to enable easier soldering.

The trio of demonstration devices is just the beginning. From here, the researchers are hopeful that their discovery could enable new forms of sensor. It’s now looking for partners and funders to help bring the idea to life.

“Having successfully demonstrated how this new bonding approach could work and be applied in laboratory prototypes, we now want to take this technology out of the lab and make it available to everyone,” Firat Güder, lead researcher from the department, said in a statement.

As fitness fans seek to quantify more of their workouts and health, a squeezy sensor could maybe bring a whole new dimension to the emerging treasure trove of data. Just as long as it’s secure.

>Abstract:

We report a method of creating solderable, mechanically robust, electrical contacts to interface (soft) silicone-based strain sensors with conventional (hard) solid-state electronics using a nanoporous Si-Cu composite. The Si-based solder-on electrical contact consists of a copper-plated nanoporous Si top surface formed through metal-assisted chemical etching and electroplating and a smooth Si bottom surface that can be covalently bonded onto silicone-based strain sensors through plasma bonding. We investigated the mechanical and electrical properties of the contacts proposed under relevant ranges of mechanical stress for applications in physiological monitoring and rehabilitation. We also produced a series of proof-of-concept devices, including a wearable respiration monitor, leg band for exercise monitoring, and squeeze ball for monitoring rehabilitation of patients with hand injuries or neurological disorders to demonstrate the mechanical robustness and versatility of the technology developed in real-world applications.
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