Patterning of a High Surface Area Liquid Metal‐Carbon Composite Film Using Laser Processing

Abstract Liquid metal is a compelling material for making soft and stretchable devices due to its high electrical conductivity and extreme stretchability. One way to pattern liquid metal is to nebulize it into small droplets, spray it onto a surface as a film, and then use a laser to “sinter” it into circuit patterns. Here, it is shown that including poly(amic acid) in the spray‐deposited film has multiple benefits: it (1) allows the unsintered regions to be removed easily, (2) lowers the power required for sintering, (3) converts to carbon upon exposure to create a carbon‐metal composite, and (4) increases the surface area of the film by 2632% compared to bulk EGaIn. The conductive liquid metal‐carbon circuits can also be transferred to a soft substrate to produce stretchable conductors. The circuits slightly increase in conductivity up to ≈30% strain and then decrease such that by 100% strain, the resistance is only ≈1.02 times its initial resistance. Lastly, the film is highly reactive with water molecules in the air, increasing in resistance over time in humid conditions. The high reactivity and surface area of the film indicate potential applications in batteries, catalysts, and capacitors. Meanwhile, the facile patterning indicates potential applications in soft circuits.