Laser-Engraved Liquid Metal Circuit for Wearable Electronics.

Shuting Liang,Fengjiao Li,Xingyan Chen,Na Song

doi:10.3390/bioengineering9020059

Abstract

Conventional patterning methods for producing liquid metal (LM) electronic circuits, such as the template method, use chemical etching, which requires long cycle times, high costs, and multiple-step operations. In this study, a novel and reliable laser engraving micro-fabrication technology was introduced, which was used to fabricate personalized patterns of LM electronic circuits. First, by digitizing the pattern, a laser printing technology was used to burn a polyethylene (PE) film, where a polydimethylsiloxane (PDMS) or paper substrate was used to produce grooves. Then, the grooves were filled with LM and the PE film was removed; finally, the metal was packaged with PDMS film. The experimental results showed that the prepared LM could fabricate precise patterned electronic circuits, such as golden serpentine curves and Peano curves. The minimum width and height of the LM circuit were 253 μm and 200 μm, respectively, whereas the printed LM circuit on paper reached a minimum height of 26 μm. This LM flexible circuit could also be adapted to various sensor devices and was successfully applied to heart rate detection. Laser engraving micro-processing technologies could be used to customize various high-resolution LM circuit patterns in a short time, and have broad prospects in the manufacture of flexible electronic equipment.

Highlights

Research on flexible wearable technologies and wearable electronic systems has been developing for a long time
We proposed and demonstrated a new printing and manufacturing strategy for liquid metal (LM) electronic circuits, denoted as laser printing-based LM electronic circuit printing
The accuracy of the laser engraving could be used to manufacture a flexible circuit with a width of 253 μm on a PDMS substrate

Summary

Introduction

Research on flexible wearable technologies and wearable electronic systems has been developing for a long time. Flexible electronic devices are characterized by their softness, stretchability, and wear resistance, and have been widely used in biomedical testing, electronic skin sensors, smart skins, photoelectricity, energy storage, and other fields [1,2,3,4,5,6]. Wearable electronic skin generally has sensors, such as stress, temperature, light, and electrochemical sensors, to measure the skin epidermis or superficial tissues. Electronic skin is made of conductive and stretchable materials, which provide compliance for the manufacture of flexible wearable devices. Flexible circuits have been generally based on metal nanoparticles, nanowires, and graphene [7]. Compared with common organic or inorganic conductive materials, such as silver nanoparticles, liquid metal (LM)

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