Design and 3D printing of paper-based shape memory polymer actuated for soft lightweight fingers

Smart materials and devices that possess multiple functions of sensing and actuation have been investigated over decades as being exploited for soft robots in various applications such as artificial muscles, biomimetic actuators, and surgical tools. One of critical requirements involved is the capability of dramatic change in shape and size to be adapted for different circumstances. Recent progress of the emerging materials has showed many remarkable properties to fabricate them in simple way. This paper reports a fused deposition modeling (FDM) method that can be simply implemented by three-dimensional (3D) printing shape memory polymer (SMP) on paper. Through 3D printing of a SMP filament on paper, the bilayer structures and grippers with a starfish shape were fabricated by exploiting the cost-effective and lightweight materials. By virtue of electrothermal actuation (Joule heating) with an electrical power supply, they showed remarkable and reversible change in shape during 100 cycles of movements. As a result, it demonstrated the capability of control over adaptive shape and size in design and fabrication of soft robots. The FDM-based method in the study is therefore beneficial to extend the flexibility in design and fabrication, as compared to the conventional ones particularly applied for rigid grippers. In the near future, a variety of multi-layer structures and materials fabricated by FDM method and 3D printing materials could be applied for applications such as soft actuators and sensors in versatile conditions.