U. ILLINOIS (US)—The concept of self-healing materials has been successfully demonstrated for polymers and is being developed for applications such as coatings on large scale structures like bridges. Now, researchers that pioneered this rapidly emerging field have shown that self-healing can also work for a critical small scale application: restoring lost conductivity in electronics.

Susan Odom, postdoctoral researcher at the University of Illinois, says a twin-microcapsule method is “the first microcapsule system for the restoration of conductivity in mechanically damaged electronic devices in which the repairing agent is not conductive until its release.”

Details of the study are available online in Advanced Functional Materials, and will serve as a cover story for the journal.

The system builds on recent work on a single capsule method for restoring conductivity, but with the added feature of being non-conductive until damage occurs and the conductivity agents are needed.

The microcapsule shells of the twin microcapsules rupture in response to the damage and the component precursor materials are released as a liquid from the core, forming a solid charge-transfer salt that restores conductivity to the electronic device.

“We’ve been able to encapsulate this conductive salt on its own but we wanted to show that we could encapsulate something that was non-conductive,” Odom says. “We only want it to be conductive when it’s actually being used in repair.”

The precursor components are encapsulated in a solution in an organic solvent. An advantage of using non-conductive liquid precursors is improved flow of the healing agent, enabling improved delivery to a damage site.

The precursor solutions are “low viscosity liquids, avoiding delivery problems of viscous solutions or suspensions,” the researchers write.

“This system has the potential to serve as a useful model for a two-part electronic self-healing system using liquid precursors by comparing the degree of restoration of conductivity of one- and two-part microcapsule systems.”

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