Variable Stiffness Conductive Composites by 4D Printing Dual Materials Alternately

可变刚度导电复合材料4D打印

Fei Long, Gaojie Xu, Jing Wang, Yong Ren*, Yuchuan Cheng*

龙菲，许高杰，王静，任勇*，程昱川*

全文链接：Micromachines, 2022, 13, 1343

Abstract

    本文研究了一种可变刚度复合材料，其由低熔点金属和有机硅弹性体组成，利用3D直写打印技术将低熔点金属封装到有机硅弹性体中。这种复合材料能够通过低熔点金属的热致相变来控制其自身在软态和刚态之间的刚度，刚度变化幅度不小于1900%。而且当温度超过低熔点金属熔点后，复合材料的材料的电阻随变形程度而变化，有望应用于软传感驱动器领域。

Materials that can be designed with programmable properties and which change in response to external stimuli are of great importance in numerous fields of soft actuators, involving robotics, drug delivery and aerospace applications. In order to improve the interaction of human and robots, materials with variable stiffness are introduced to develop their compliance. A variable stiffness composite has been investigated in this paper, which is composed of liquid metals (LMs) and silicone elastomers. The phase changing materials (LMs) have been encapsulated into silicone elastomer by printing the dual materials alternately with three-dimensional direct ink writing. Such composites enable the control over their own stiffness between soft and rigid states through LM effective phase transition. The tested splines demonstrated that the stiffness changes approximately exceeded 1900%, and the storage modulus is 4.75 MPa and 0.2 MPa when LM is rigid and soft, respectively. In the process of heating up, the stretching strain can be enlarged by at least three times, but the load capacity is weakened. At a high temperature, the resistance of the conductive composites changes with the deformation degree, which is expected to be applied in the field of soft sensing actuators.