‘Soft Devices’ Get Boost from New Bonding Technique

From Next Big Future

New method for bonding soft materials will enable more complex wearable smart devices

Combining multiple soft materials into a complex machine requires many new innovations.

Current methods to combine soft materials are limited, relying on glues or surface treatments that can restrict the manufacturing process. For example, it doesn’t make much sense to apply glue or perform surface treatment before each drop of ink falls off during a 3D printing session.

New bonding methods can join various hydrogels and elastomers in various manufacturing processes without sacrificing the properties of the materials.

The researchers focused on the two most-used building blocks for soft devices, hydrogels (conductors) and elastomers (insulators). To combine the materials, the team mixed chemical coupling agents into the precursors of both hydrogels and elastomers. The coupling agents look like molecular hands with small tails. As the precursors form into material networks, the tail of the coupling agents attaches to the polymer networks, while the hand remains open. When the hydrogel and elastomer are combined in the manufacturing process, the free hands reach across the material boundary and shake, creating chemical bonds between the two materials. The timing of the “handshake” can be tuned by multiple factors such as temperature and catalysts, allowing different amounts of manufacturing time before bonding happens.

The researchers showed that the method can bond two pieces of casted materials like glue but without applying a glue layer on the interface. The method also allows coating and printing of different soft materials in different sequences. In all cases, the hydrogel and elastomer created a strong, long-lasting chemical bond.

“The manufacturing of soft devices involves several ways of integrating hydrogels and elastomers, including direct attachment, casting, coating, and printing,” said Canhui Yang, a postdoctoral fellow at SEAS and co-first author of the paper. “Whereas every current method only enables two or three manufacturing methods, our new technique is versatile and enables all the various ways to integrate materials.”

 

New method for bonding soft materials will enable more complex wearable smart devices
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