Direct Writing of Flexible Electronics through Room Temperature Liquid Metal Ink

Abstract

BackgroundConventional approaches of making a flexible circuit are generally complex, environment unfriendly, time and energy consuming, and thus expensive. Here, we describe for the first time the method of using high-performance GaIn10-based electrical ink, a significantly neglected room temperature liquid metal, as both electrical conductors and interconnects, for directly writing flexible electronics via a rather easy going and cost effective way.MethodsThe new generation electric ink was made and its wettability with various materials was modified to be easily written on a group of either soft or rigid substrates such as epoxy resin board, glass, plastic, silica gel, paper, cotton, textiles, cloth and fiber etc. Conceptual experiments were performed to demonstrate and evaluate the capability of directly writing the electrical circuits via the invented metal ink. Mechanisms involved were interpreted through a series of fundamental measurements.ResultsThe electrical resistivity of the fluid like GaIn10-based material was measured as 34.5 µΩ·cm at 297 K by four point probe method and increased with addition of the oxygen quantity, which indicates it as an excellent metal ink. The conductive line can be written with features that are approximately 10 µm thick. Several functional devices such as a light emitting diode (LED) array showing designed lighting patterns and electrical fan were made to work by directly writing the liquid metal on the specific flexible substrates. And satisfactory performances were obtained.ConclusionsThe present method opens the way to directly and quickly writing flexible electronics which can be as simple as signing a name or drawing a picture on the paper. The unique merit of the GaIn10-based liquid metal ink lies in its low melting temperature, well controlled wettability, high electrical conductivity and good biocompability. The new electronics writing strategy and basic principle has generalized purpose and can be extended to more industrial areas, even daily life.

Flexible Sub-THz Metal Wire Grid Polarizer Based on an EGaIn<formula> <tex>$_{24.5}$</tex> </formula> Alloy

“…Metals are weighted 75.5:24.5 and they are kept in de-ionized water to reduce the development of oxide skin that specially characterizes Gallium and its alloys [12]. As the EGaIn 24.5 is liquid at room temperature and has high surface tension, sheets of vinyl acetate monomer offer good adherence, avoiding the formation of droplets of alloy that can blur the result [9].…”

“…Several studies deal with the determination of the role of the alloy oxidation, when studying its rheological properties [9], [12], [14]. The solid-like response of EGaIn 24.5 and its high wettability are actually due to the compact, stable and homogeneous oxide skin that quickly forms on the droplet surface when it is exposed to air, avoiding the oxidation of the whole alloy (i.e.…”

“…Polarizers based on ink-jet printing exploit the conductive properties of metal inks based on Silver or Aluminum nanoparticles [7], [8]. The former type requires a rather complex and expensive process of fabrication in addition to specific printers of considerable cost [8], [9]. On the other hand, Aluminum based inks are more affordable, but they provide lower performance than Silver based ones [8], because of their higher resistivity (ρ Ag = 1.59 · 10 −6 Ωcm < ρ Al = 2.65 · 10 −6 Ωcm [10]).…”

Recent Advances in Soft E-Textiles

“…The addition of electronic components to these fabrics would create a fully new range of functional clothing. Optical light emitting diodes (OLEDs), nanoelectronics, conducting liquid metals, etc., in fiber form could lead to revolutionary applications by integrating optical, optoelectronic, flexible, and stretchable devices with textiles [61,62]. Recently, Levi's musical jacket prepared by the Media Lab at Massachusetts Institute of Technology (MIT), USA, includes a flexible and durable embroidered fabric keyboard.…”

Fast Fabrication of Flexible Functional Circuits Based on Liquid Metal Dual‐Trans Printing

“…For this strategy, the alloy's wettability with the substrate is one of the core factors that determine the ink deposition quality. In our earlier work, a tapping mode liquid metal delivery technique has been developed to improve the wettability of liquid metals on substrates, [30][31][32] which performs very well on the polyvinyl chloride (PVC) plastic fi lm. [ 31 ] As for soft substrate, the polydimethylsiloxane (PDMS) features better elasticity and biocompatibility.…”