Tape Transfer Printing of a Liquid Metal Alloy for Stretchable RF Electronics

Abstract

In order to make conductors with large cross sections for low impedance radio frequency (RF) electronics, while still retaining high stretchability, liquid-alloy-based microfluidic stretchable electronics offers stretchable electronic systems the unique opportunity to combine various sensors on our bodies or organs with high-quality wireless communication with the external world (devices/systems), without sacrificing enhanced user comfort. This microfluidic approach, based on printed circuit board technology, allows large area processing of large cross section conductors and robust contacts, which can handle a lot of stretching between the embedded rigid active components and the surrounding system. Although it provides such benefits, further development is needed to realize its potential as a high throughput, cost-effective process technology. In this paper, tape transfer printing is proposed to supply a rapid prototyping batch process at low cost, albeit at a low resolution of 150 μm. In particular, isolated patterns can be obtained in a simple one-step process. Finally, a stretchable radio frequency identification (RFID) tag is demonstrated. The measured results show the robustness of the hybrid integrated system when the tag is stretched at 50% for 3000 cycles.

Implantable liquid metal-based flexible neural microelectrode array and its application in recovering animal locomotion functions

“…Recently, the eutectic GaIn alloy has been found to own several intrinsic merits, such as good electrical conductivity [20,21], thermal performance [22] and radiation imaging capability [23] (metal features); liquidity and compliance [24] (liquid properties). With a broad temperature range of liquid phase, the room temperature liquid metal GaIn alloy (75.5% Ga, 24.5% In by weight) displays zero stiffness and almost infinite stretchability due to its fluidity, which is super compliant in vivo.…”

Selectively plated stretchable liquid metal wires for transparent electronics

“…The SLMP process can produce various conductive complex micropatterns containing features that have planar dimensions less than 10 m with higher resolution and uniform edges. Compared with the previous liquid metal printing methods, the accuracy of manufacture is significantly improved [34][35][36][37]. The I-V characteristics demonstrate that the LED-integrated stretchable circuit has stable electrical and mechanical properties, even after twisting (180 • ) and stretching (60%) for 6000 repetitions.…”

“…Owing to the extra demand of a needle and syringe for liquid-metal injection or printing, these manual methods have constraints in geometry and high-volume manufacturing. Hyperelastic circuits have been produced by other techniques, such as laser patterning, stencil masks, and masked deposition [34][35][36][37]. Despite these remarkable achievements, the developed liquidmetal printing techniques cannot satisfy the increasing demand of SCB applications owing to the low resolution (pattern planar dimension >100 m) and irregular edge [34][35][36][37].…”

Polyurethane foam coated with a multi-walled carbon nanotube/polyaniline nanocomposite for a skin-like stretchable array of multi-functional sensors

“…29,30 The sticky property of the film enhances the wetting of the liquid metal on the substrate surface. 31 Furthermore, formation of the gallium-oxide skin during the direct printing process allows the written pattern to maintain its printed shape, even after the encapsulation process with elastomer. The mechanical stability of the Galinstan interconnection was confirmed by the fact that there was no noticeable change in resistance under stretching up to 50%, and more detailed characteristics of the liquid metal pattern obtained using the XYZ printer are also illustrated in Supplementary Figure S6.…”