Liquid-Metal-Coated Magnetic Particles toward Writable, Nonwettable, Stretchable Circuit Boards, and Directly Assembled Liquid Metal-Elastomer Conductors

Liquid metal is a promising conductor material
for producing soft and stretchable circuit “boards”
that can enable next-generation electronics by electrically connecting
and mechanically supporting electronic components. While liquid metal
in general can be used to fabricate soft and stretchable circuits,
magnetic liquid metal is appealing because it can be used for self-healing
electronics and actuators by external magnetic fields. Liquid metal
can be rendered into particles that can then be used for sensors and
catalysts through sonication. We used this feature to produce “novel”
conductive and magnetic particles. Mixing ferromagnetic iron particles
into the liquid metal (gallium) produces conductive ferrofluids that
can be rendered into gallium-coated iron particles by sonication.
The gallium shell of the particles is extremely soft, while the rigid
iron core can induce high friction in response to mechanical pressure;
thus, hand-sintering of the particles can be used to directly write
the conductive traces when the particles are cast as a film on elastic
substrates. The surface topography of the particles can be manipulated
by forming GaOOH crystals through sonication in DI water, thus resulting
in nonwettable circuit boards. These gallium-coated iron particles
dispersed in uncured elastomer can be assembled to form conductive
microwires with the application of magnetic fields.