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

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 & AP;30% strain and then decrease such that by 100% strain, the resistance is only & AP;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. This study explores adding polyamic acid (PAA) to eutectic gallium-indium (EGaIn) particle films prior to laser processing. It is found that adding PAA decreases the required laser power for sintering, results in a liquid metal-carbon composite, helps remove unsintered regions, and increases surface area. After laser exposure, the EGaIn-carbon films are conductive, highly stretchable, and demonstrate strain-invariant resistance.image

Automated summary

Liquid metal-carbon composite films were fabricated by adding poly(amic acid) (PAA) to eutectic gallium-indium (EGaIn) particle films prior to laser processing. The addition of PAA decreased the required laser power for sintering, resulted in a liquid metal-carbon composite, helped remove unsintered regions, and increased surface area. The conductive films showed high stretchability and strain-invariant resistance up to a certain strain level. However, the films exhibited high reactivity with water molecules in the air, leading to an increase in resistance over time in humid conditions.