Spray-On Liquid-Metal Electrodes for Graphene Field-Effect Transistors

Abstract

Advancements in flexible circuit interconnects are critical for widespread adoption of flexible electronics. Non-toxic liquid-metals offer a viable solution for flexible electrodes due to deformability and low bulk resistivity. However, fabrication processes utilizing liquid-metals suffer from high complexity, low throughput, and significant production cost. Our team utilized an inexpensive spray-on stencil technique to deposit liquid-metal Galinstan electrodes in top-gated graphene field-effect transistors (GFETs). The electrode stencils were patterned using an automated vinyl cutter and positioned directly onto chemical vapor deposition (CVD) graphene transferred to polyethylene terephthalate (PET) substrates. Our spray-on method exhibited a throughput of 28 transistors in under five minutes on the same graphene sample, with a 96% yield for all devices down to a channel length of 50 μm. The fabricated transistors possess hole and electron mobilities of 663.5 cm2/(V·s) and 689.9 cm2/(V·s), respectively, and support a simple and effective method of developing high-yield flexible electronics.

Aerosol Spray Deposition of Liquid Metal and Elastomer Coatings for Rapid Processing of Stretchable Electronics

“…The nozzle directs a stream of particles onto a substrate until the particles cover the surface with a complete film. This process is compatible with a variety of substrates, as seen in prior work [ 52 , 54 , 55 , 56 , 59 , 62 , 63 , 64 , 65 , 66 ]. While others have shown that patterning is possible using a directed laser to ablate liquid metal from the surface [ 53 ], here we make use of vinyl stencils (also commonly used in the crafting community) adhered to the substrate to pattern the metal.…”

Low-Cost Rapid Fabrication of Conformal Liquid-Metal Patterns

“…Moreover, the scraping technique can be automated by mounting the needle to the printhead of a 3D printer, as illustrated in Figure 11. In addition to the transmission line and antenna demonstrated here, this method of spraying LM was used to create LM contacts for a graphene transistor [27].…”

Liquid Metal Direct Write and 3D Printing: A Review

“…By spraying through a stencil, electrically conductive features can be rapidly produced onto a variety of substrates. This technique has been used to manufacture electrodes, [87,88] inertial and strain sensors, [84,89] wireless power transmission coils, [90] and connections for thermal energy harvesters. [91] Using a stencil (which deviates from true direct-write techniques) also enables patterning on substrates with complex topography.…”