Laser Writing of Eutectic Gallium–Indium Alloy Graphene‐Oxide Electrodes and Semitransparent Conductors

Abstract

Graphene encapsulated liquid metal particles is a novel and promising class of biphasic composite, with application in the next generation of electronic devices. Here, rapid, low‐cost, and scalable fabrication of solution processed large area rGO@EGaIn electrodes is demonstrated. rGO@EGaIn solution is first deposited over the substrate through spray coating, and then processed through a low‐cost laser (master oscillator power amplifier (MOPA)). This allows simultaneous reduction, thinning, ablation, and high resolution patterning of the deposited films. Surprisingly, it is found that by adjusting the laser parameters, it is possible to make semitransparent conductors via laser thinning of the films. Scanning electronic microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDS) spectroscopy confirm that although the rGO/EGaIn weight ratio is only ≈0.08, the composite has a considerably different microstructure compared to the eutectic gallium–indium alloy (EGaIn) particles alone. Graphene oxide (GO) protects the EGaIn from extreme morphology change under laser irradiation. Therefore, various “shades” of rGO@EGaIn can be fabricated in a single film. This allows development of large electrodes with complex geometries in a few seconds. The conductivity, transparency, and reduction of the laser processed films are characterized by several techniques and an example of application is demonstrated by laser patterning a highly sensitive breath‐monitoring sensor.

Graphene‐Assisted Chemical Stabilization of Liquid Metal Nano Droplets for Liquid Metal Based Energy Storage

“…The electrode geometry was custom-made through a simple and accessible 1064 nm wavelength inferred (IR) laser patterning method. [31] Thanks to the symmetric architecture, the full film of the CCs, and electrodes can be pre-coated and then rapidly turned into the desired shape through laser patterning. Figure 1C shows a thin-film SC created as an example and depicts how it can be bent, twisted, or rolled.…”

The role of printed electronics and related technologies in the development of smart connected products

“…These inherently stretchable materials circumvent the need to use constituents with different stretching and flexural moduli, as the ones presented above. Such formulations include eutectic indium gallium (eGaIn) alloys, silver-based solutions, and stretchable polymers [70,[105][106][107][108]. Among the stretchable polymeric conductors and semi-conductors, the most employed in literature are poly(3-hexylthiophene-2,5-diyl) (P3HT), Polyaniline (PANI), Polypyrrole, and poly(3, 4ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), whose viscosity can be modified to render them more compliant with stretching and less brittle [83,109].…”

Self‐Healing, Reconfigurable, Thermal‐Switching, Transformative Electronics for Health Monitoring

“…The thin oxide layer (≈3 nm) [40] rapidly formed on the outside surface of eGaIn also helps maintain mechanical stability but results in high surface tension (≈600 mN m −1 ) [41] and poor adhesion create challenges in printing. Efforts to improve printability include laser sintering, [42,43] electrowetting, [44] microchannels, [45] 3D printing, [46] and metal doping. [47][48][49] However, it is still challenging to maintain high electrical performance in the printed circuits, provide easy integration with commercial-off-the-shelf (COTS) components, [50,51] and recycle electronics to minimize e-waste for reduced health and environmental issues.…”