An autonomously electrically self-healing liquid metal–elastomer composite for robust soft-matter robotics and electronics

Large-area stretchable electronics are critical for progress in wearable computing, soft robotics and inflatable structures. Recent efforts have focused on engineering electronics from soft

materials—elastomers, polyelectrolyte gels and liquid metal. While these materials enable elastic compliance and deformability, they are vulnerable to tearing, puncture and other mechanical

damage modes that cause electrical failure. Here, we introduce a material architecture for soft and highly deformable circuit interconnects that are electromechanically stable under typical

loading conditions, while exhibiting uncompromising resilience to mechanical damage. The material is composed of liquid metal droplets suspended in a soft elastomer; when damaged, the

droplets rupture to form new connections with neighbours and re-route electrical signals without interruption. Since self-healing occurs spontaneously, these materials do not require manual

repair or external heat. We demonstrate this unprecedented electronic robustness in a self-repairing digital counter and self-healing soft robotic quadruped that continue to function after

significant damage.

The authors acknowledge support from the NASA Early Career Faculty Award (NNX14AO49G; Research Collaborator: B. Bluethmann) and AFOSR Multidisciplinary University Research Initiative

(FA9550-18-1-0566; Program Manager: K. Goretta). M.D.B. also acknowledges support from Iowa State University start up funds. Sensor and mechanical characterization was performed on equipment

supported through an Office of Naval Research (ONR) Defense University Research Instrumentation Program (DURIP) (N00014140778; Bioinspired Autonomous Systems; Program Manager: T. McKenna).

These authors contributed equally: Eric J. Markvicka, Michael D. Bartlett.

Integrated Soft Materials Lab, Carnegie Mellon University, Pittsburgh, PA, USA

Robotics Institute, Carnegie Mellon University, Pittsburgh, PA, USA

Material Science & Engineering, Iowa State University, Ames, IA, USA

Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA

E.J.M., M.D.B., X.H. and C.M. designed the research; E.J.M., M.D.B. and X.H. performed the research; E.J.M., M.D.B., X.H. and C.M. analysed the data; E.J.M., M.D.B. and C.M. wrote the paper.

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1 supplementary note with 1 reference, Supplementary Figures 1–11

Electrical activation of LM composite. The video illustrates the electrical activation of the LM composite using a 2D plotter and the ability to pattern geometrically intricate designs

Elapsed time counter with autonomously self-healing electronics. The video illustrates the ability of the composite to autonomously self-heal under extreme damage without manual

intervention, use of external energy sources, or redundant electronics. A complementary illustration is shown with traditional electrical wiring, which immediately fails after damage

Elapsed time counter with selectively patterned autonomously self-healing electronics. The video demonstrates the ability of the composite to be selectively patterned and autonomously

self-heal under extreme damage without unintended electrical shorting, without manual intervention, use of external energy sources, or redundant electronics

Electrical stability of the autonomously self-healing electronics under normal walking conditions. The video demonstrates the ability of the composite to undergo normal walking conditions

for up to 31 steps with 10 footwear variations

An autonomously self-healing soft robot. The video demonstrates the ability to use the self-healing composite for soft robots that require on-board circuitry that are resistant to damage and

can support large bursts of electrical power

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