Variable Stiffness Conductive Composites by 4D Printing Dual Materials Alternately

Fei Long; Gaojie Xu; Jing Wang; Yong Ren; Yuchuan Cheng

doi:10.3390/mi13081343

Variable Stiffness Conductive Composites by 4D Printing Dual Materials Alternately

Micromachines (Basel). 2022 Aug 19;13(8):1343. doi: 10.3390/mi13081343.

Authors

Fei Long^{1

2

3}, Gaojie Xu¹, Jing Wang⁴, Yong Ren^{2

3

5}, Yuchuan Cheng^{1

6}

Affiliations

¹ Zhejiang Key Laboratory of Additive Manufacturing Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.
² Department of Mechanical, Materials and Manufacturing Engineering, University of Nottingham Ningbo China, Ningbo 315100, China.
³ Research Group for Fluids and Thermal Engineering, University of Nottingham Ningbo China, Ningbo 315100, China.
⁴ Department of Electrical and Electronic Engineering, University of Nottingham Ningbo China, Ningbo 315100, China.
⁵ Key Laboratory of Carbonaceous Wastes Processing and Process Intensification Research of Zhejiang Province, University of Nottingham Ningbo China, Ningbo 315100, China.
⁶ Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.

Abstract

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.

Keywords: 4D printing; liquid metal; phase change; thermal response; variable stiffness.

Abstract

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