Soft and Stretchable Liquid Metal Composites with Shape Memory and Healable Conductivity

Shape
memory composites are fascinating materials with the ability
to preserve deformed shapes that recover when triggered by certain
external stimuli. Although elastomers are not inherently shape memory
materials, the inclusion of phase-change materials within the elastomer
can impart shape memory properties. When this filler changes the phase
from liquid to solid, the effective modulus of the polymer increases
significantly, enabling stiffness tuning. Using gallium, a metal with
a low melting point (29.8 °C), it is possible to create elastomeric
materials with metallic conductivity and shape memory properties.
This concept has been used previously in core–shell (gallium-elastomer)
fibers and foams, but here, we show that it can also be implemented
in elastomeric films containing microchannels. Such microchannels
are appealing because it is possible to control the geometry of the
filler and create metallically conductive circuits. Stretching the
solidified metal fractures the fillers; however, they can heal by
body heat to restore conductivity. Such conductive, shape memory sheets
with healable conductivity may find applications in stretchable electronics
and soft robotics.