Hydrogel Electronics

Hydrogels are a lot like people: squishy and made mostly of water. That makes these soft materials attractive supports for biomedical devices, such as implantable sensors and diagnostic wound dressings, because their properties are similar to biological tissue. But hydrogels are difficult to interface with electronics that are rigid and easily damaged by water, says Xuanhe Zhao of Massachusetts Institute of Technology. Zhao and his team overcame this problem by developing a way to make hydrogels cling to electronic components while staying flexible and stretchy like tissue (Adv. Mater. 2015, DOI: 10.1002/adma.201504152). To improve the bond between electronics and hydrogels, the researchers first encased active electronic components, such as light-emitting diodes, in a silicone elastomer. They then fixed the silicone to a thin piece of glass and functionalized the glass surface with 3-(trimethoxysilyl)propyl methacrylate. The methacrylate-functionalized surface bound with polyacrylamide in the team’s hydrogel. The covalent bonds hold the electronic hydrogel device together, even as it bends and stretches, Zhao says.