Three-dimensional circuit fabrication using four-dimensional printing and direct ink writing

Three-dimensional (3D) circuit has good properties such as compact design, shape conformity, and better performance. The spatial layout of a 3d circuit design, however, adds difficulty and complexity in the fabrication process. In this paper, a hybrid process of four-dimensional (4D) printing and Direct Ink Writing is developed to implement customized 3D circuit design. In the process, a two-dimensional (2D) foldable structure with a heat-triggered self-folding mechanism is fabricated. On the structure the conductive circuit traces are printed that will transform its shape with the foldable structure in a heating environment. Hence the 3D circuit design can be achieved by using the 2D direct ink writing process. The 4D printing process provides a potentially faster and effective way of fabricating 3D circuit design. Process parameters as well as design considerations are analyzed in the paper. Verification test cases are performed to demonstrate the feasibility of the developed method. Potential applications are also discussed.