Making wearable sensors stick to the body

Poly vinyl alcohol becomes wearable sensor adhesive
A film made of 4C3-PVA remained stuck to two pig skin surfaces when they were separated (top); an unmodified PVA film did not (bottom). (American Chemical Society)

One of the challenges in getting wearable sensors to work properly is to make sure the devices stay next to the skin. In a study described in ACS Omega, researchers tweaked a widely used polymer to potentially create a new adhesive to keep these sensors in place.

According to researchers, the acrylic-based medical bandages commonly used can provoke allergic reactions or cause pain when removed. Another option, silicone-based adhesives, is not irritating but also doesn't stay put. Other adhesives, including bio-inspired ones that mimic gecko feet and octopus suckers, are not yet practical for mass production.

To develop a better alternative, researchers Xi Chen and Tetsushi Taguchi turned to a polymer, poly (vinyl alcohol) (PVA), which is not irritating to the skin and is currently used in some wound dressings, contact lenses and other similar items.

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Because PVA can come off easily when wet, the researchers modified the compound by adding alkyl chains to try to improve its adhesion. They made versions with chains that contained three, six or nine methylene carbons, then tested them to see which performed best. It turned out that films made of longer chain versions were more hydrophobic, but had less tensile strength. Cells best tolerated the short chain known as 4C3-PVA, and in tests with pig skin, they found it bonded most strongly.

The researchers conclude that 4C3-PVA is a promising adhesive for wearable devices.

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