Researchers create new silver hydrogel composite for bioelectronics

Metals play a key role for strength, electrical conductivity, and durability in robotics. However, due to the heavy weight and rigidness of metals, they are undesirable for soft and fluid systems for wearable computing devices and human-machine interfaces.

On the other hand, hydrogels are lightweight, biocompatible, stretchable that makes them excellent materials for tissue engineering scaffolding and contact lenses. On the downside, hydrogels are poor at conducting electricity, which is required for bioelectronics and digital circuits.

In a new development, researchers at the Soft Machines Lab, Carnegie Mellon University have developed a unique silver- based hydrogel composite. The material has high electrical conductivity and can deliver direct current, and at the same time maintain deformability and soft compliance. The findings of the study is published in Nature Electronics.

For the study, the team suspended flakes of size of a micrometer in a hydrogel matrix of polyacrylamide alginate. After a partial dehydration process, the flakes shape into percolating networks with electrical conductivity and robust for mechanical deformations. In fact, by manipulation of the hydration and dehydration process, the flakes can be molded to stay attached or break apart to lead to reversible electrical connections.

Meanwhile, previous attempts to combine hydrogels and metals revealed a trade-off between improved conductivity and reduced compliance and deformability. To address this, the team of researchers sought to tackle the challenge with efforts to augment their expertise in developing conductive, stretchable elastomers using liquid metal.

“Importantly, featuring high electrical conductivity and high compliance, the new composite can have several applications in bioelectronics and more,” explained the lead researcher of the study. A sticker for the brain equipped with sensors for signal processing is an example of the new composite.