Manpreet Kaur1 Woo Soo Kim1

1, Simon Fraser University, Surrey, British Columbia, Canada

Soft robotics have received increasing attention over recent years due to their apparent advantages of high flexibility and compliant nature. As a result, intensive research is focused in the development of flexible materials that possess extraordinary mechanical properties.1 Soft materials featuring both three-dimensional (3D) mechanical architectures and high stretchability are highly desirable for a number of engineering applications ranging from soft robots to stretchable electronics. This enables the achievement of complex movements with more adaptability than traditional rigid arrangements.
Here, we present design, fabrication, and characterization of a fully integrated 3D printed soft humanoid robotic hand shaped with mechanical meta-material and integrated with a shape memory alloy (SMA) actuator. A mechanical meta-material truss designed with auxetic is used for the robotic body. This 3D printed truss is mainly responsible to provide high strength - to - weight ratio as well as required bending durability due to its different Poison’s ratio. As these soft robots have infinite DOF and largely rely on material deformation for controlling, the metamaterial body is carefully designed to allow desired motion while restricting motions in other directions. Manufacturing of soft robots is also extremely challenging as traditional methods used for rigid robots cannot be applied. Therefore, multi-material based 3D printing technology is demonstrated with capability of 3D printed soft robotics with precision, through extrusion of both flexible and rigid polymer materials.2 The different structures are fabricated together in a single step to form the robotic body.3 Shape memory alloys (SMA) can be easily integrated in 3D printed micro-trusses without requiring huge spaces and, complex gearing mechanisms, thus reducing the production costs. The actuators are inserted into the 3D printed micro-trusses and heated via Joule heating from an applied current. Finally, SMA assisted actuation of truss-based soft robotic fingers are demonstrated. This SMA actuated soft robot can be further used along with an embedded strain sensor having micro-trusses with the negative Poisson ratio can lead to improve sensor sensitivity than that of auxetic foam based sensors.4

1. R. L. Truby and J. A. Lewis: Printing soft matter in three dimensions. Nature 540(7633), 371 (2016).
2. M. Kaur, S. M. Han, and W. S. Kim: Three-dimensionally printed cellular architecture materials: perspectives on fabrication, material advances, and applications. MRS Commun. 1 (2016).
3. M. Kaur, T. GwangYun, S. Han, E. L. Thomas, and W. S. Kim: 3D printed stretching-dominated micro-trusses. Mater. Des. 134, 272 (2017).
4. Y. Li, S. Luo, M. C. Yang, R. Liang, and C. Zeng: Poisson Ratio and Piezoresistive Sensing: A New Route to High-Performance 3D Flexible and Stretchable Sensors of Multimodal Sensing Capability. Adv. Funct. Mater. 2900 (2016).