Direct Writing of Flexible Electronics through Room Temperature Liquid Metal Ink

Haiyan Li,Arum Han,Yunxia Gao,Jing Liu

doi:10.1371/journal.pone.0045485

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.

Highlights

The application of flexible electronics is growing rapidly, as promoted by a group of newly emerging areas
Breakthroughs made will benefit the rapid development of modern consumer electronics including flexible displays [1,2,3], conformal antenna arrays, thin film transistors [4,5,6,7], membrane keyboards, electronic solar cell arrays [8,9], radio-frequency identification (RFID) tags [10], flexible batteries [11,12], and electronic circuits fabricated in e.g. clothing or biomedical devices etc. [13,14,15,16]
The directly printing techniques such as nanoimprinting [17], screen printing [18] and ink jet imprinting [19,20,21] have emerged as attractive direct patterning techniques and promoted a big development in flexible electronics fabrication fields

Summary

Introduction

The application of flexible electronics is growing rapidly, as promoted by a group of newly emerging areas. The conventional electrical circuit fabrication technologies are subject to limitations in that they request multistep, involve high processing temperatures and toxic waste and are more expensive. The directly printing techniques such as nanoimprinting [17], screen printing [18] and ink jet imprinting [19,20,21] have emerged as attractive direct patterning techniques and promoted a big development in flexible electronics fabrication fields. Conventional approaches of making a flexible circuit are generally complex, environment unfriendly, time and energy consuming, and expensive. We describe for the first time the method of using high-performance GaIn10based 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

Methods

Results

Conclusion