可拉伸导体的印刷制备概述

Overview of Preparation of Stretchable Conductors by Printing

可穿戴电子器件可应用于电子皮肤、人体运动监测、医疗健康行业中,是当前印刷电子领域的研究热点之一,但可穿戴电子应用面临的一个重要挑战是器件的突兀性。可拉伸导体是实现可穿戴电子器件突兀性最小化的关键技术。根据制备方法,可拉伸导体可分为两类。一种是直接利用本质上可拉伸的功能材料实现可拉伸,获得抵抗应变的可靠电导,即将导电填料与弹性聚合物混合或嵌入到弹性基质上获得,可提高导电网络的机械稳定性,且导电组分难以从基质上脱落。这种方法制备的导体拉伸性有限(通常低于30%形变,如果大于40%形变电阻增加2倍以上),或者由于大量绝缘弹性聚合物的存在使本身导电性较差。另一种是通过巧妙的结构将具有不同作用的元件组合成一个整体,获得抵抗应变的可靠电导,包括通过可变形的导线将各个微电子结构连接起来形成岛桥结构,或者设计成开放网格式的结构利用面内转动实现可拉伸。这种方法不是本质上可拉伸,而是依靠结构改变来承受大的应变,但结构设计制造过程复杂,并且在拉伸之后不能完全恢复原始形貌,限制了其导电功能和机械拉伸稳定性。因此,基于内在完全可拉伸元件的可拉伸电子器件的发展受到极大关注。为了制备具有二维平面结构、本质上可拉伸的导体,使其具有较好的导电性和机械拉伸稳定性,往往需要将两种方法结合在一起,如采用真空沉积、光刻等方法制备含有金属网的弹性膜。然而,这些制备工艺属于减法过程,工艺复杂、成本高、无法规模化,难以用于大面积电子中。印刷作为一种快速图案化技术,通过印刷可溶液化的弹性复合导电油墨,可以实现以较低成本制备平面图案化、本质上可拉伸的导体。因此,开发与印刷设备、工艺兼容的弹性复合导电油墨成为关键技术。本文介绍了弹性复合导电油墨的类型与制备及可拉伸导体图案的印刷技术,分析当前可拉伸导体应用的限制,为突破其在可穿戴传感器中的应用限制提供参考。

Wearable electronic device can be used in electronic skin,human motion monitoring,medical and health industry,it becomes one of research hotspots in the field of printed electronics.However,the unobtrusiveness of wearable electronic devices is an important challenge for wearable electronic applications.Stretchable conductor is the key technology to minimize the unobtrusiveness of wearable electronic devices.According to the preparation method,stretchable conductors can be divided into two categories.One is directly use of the essential and stretc-hable functional materials to achieve reliable conductance to resist strain.The mechanical stability of conductive networks can be improved by mixing conductive fillers with elastic polymers or embedding them into elastic substrates,and the conductive components are difficult to fall off from the substrates.The conductors fabricated by this method have limited tensile properties(generally less than 30%deformation,resistance will be increased by more than two times if more than 40%deformation),or poor electrical conductivity due to the presence of a large number of insulating elastic polymers.The other is to integrate the elements with different functions by structure design to obtain reliable conductance against strain.It includes connecting micro-electronic structures to form island-bridge structures by stretchable wires,or designing open grid structures to achieve stretchability by in-plane rotation.This method can withstand large strains by structure deformation,and is not essentially stretchable.However,the design and manufacture of structure are complicated,and the original morphology cannot be completely restored after repeated stretching.Thus its electrical conductivity and mechanical tensile stability is limited.Therefore,the development of stretchable electronic devices based on intrinsically fully stretchable components has attracted great attention.In order to prepare intrinsically stretchable conductors with two-dimensional planar structure with good conductivity and mechanical stretchability,it is necessary to combine the two above methods.Elastic film with metal mask prepared by vacuum deposition and photolithography.However,these preparation processes belong to subtraction process,which is complex,costly and can not be scaled up,and it is difficult to acquire large-area electronics.Printing technology,as a fast patterning technology,can be used for the preparation of planar patterned and intrinsically stretc-hable conductors at a lower cost by using soluble and elastic composite conductive ink.Therefore,the development of elastic composite conductive ink compatible with printing equipment and process is the key technologies.In this paper,the types and preparation of elastic composite conductive ink and printing technologies of stretchable conductor patterns are introduced.The limitations of current stretchable conductor application are analyzed,which can provide reference for breaking through the limitations of wearable sensor application.