Stretchy, squeezable soft sensors use tear-proof bonding method

Stretchy, squeezable soft sensors benefit from new bonding method
Imperial College London bioengineers have found a way to create stretchy and squeezy soft sensing devices by bonding rubber to electrical components. (Michael Kasimatis/Imperial College London)

For wearable applications, the ability for sensors to be flexible and conform to the surface they’re used on is important. Researchers at Imperial College in London have found a way to create stretchy and squeezy soft sensing devices by bonding rubber to electrical components, according to an article by Hayley Dunning appearing on the university’s website.

According to the article, the method developed by the researchers creates a very strong bond between force-sensitive soft materials and electrical components. The bond is so strong that the stretchy rubber itself breaks before the bond between the two different materials does. The study’s results are published in ACS Applied Materials & Interfaces.

Applications for the flexible sensors are many, including sports and rehabilitation after injury or stroke. One possibility, according to the article, are soft electrical force sensors in the form for a squeeze ball that could monitor the rehabilitation of patients with hand injuries or neurological disorders.

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While such sensors have been under development a long time, none have made it to market, because they cannot easily be integrated with electronic components, like the wires, computer chips and batteries needed to gather, process and send the data the sensor collects.

First author Michael Kasimatis, from the Department of Bioengineering at Imperial, said: "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.

"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."

Previous bonding methods revolved around using adhesives to bond force-sensitive, conductive rubbers with electrical components, which often came apart when pulled, or using metal clamps, which could tear the stretchy material.

The new method instead uses small pieces of metal-coated silicon, which chemically bond the stretchy and squeezy rubber. The silicon contacts are smooth on one side, where they bond to the rubber, and pitted and plated with copper on the other side, so wires or other electric components can be easily attached via conventional methods such as soldering.

The researchers demonstrated how their bonding method can resist the strains of stretching, and also tested it out in a few prototype sensors that could be used in healthcare and rehabilitation. Examples include a wearable breathing monitor, a leg band for exercise monitoring and a squeezy ball for monitoring hand rehabilitation.

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