Coiled Shape Memory Alloy (CSMA) Actuators and Conductive Filament for the Realization of 3D Printed Robots




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Soft robots and humanoids need actuators with low profile, lightweight, high strain and relatively high frequency. Coiled shape memory alloy (CSMA) actuators satisfy these requirements, as SMAs are high-energy density actuators. There are a number of variables that affect the performance of the CSMA actuators. We present the manufacturing, characterization and simulation of the NiTi based CSMA actuators mainly focusing on the geometry and performance relationships. The manufacturing technique resulted in 80% strain with respect to loaded length and greater than 1000% with respect to original length, when actuated with an input voltage of 3.4 V, 0.66 A, and 6 MPa load. The strain response at different frequency was determined experimentally and these actuators can be used in many soft robots. To improve actuation speed, a novel 2-step hot-cold water-cooling was implemented. One of the requirements of fully functional 3D printed robots is electrical connections in some part of the printed structure. To this effort, we present composite materials consisting of conductive carbon nanoparticles, thermoplastics, and solvents to create filaments for 3D printing. The mechanical and electrical properties of filaments were investigated using a concentration of 0 − 15% weight of carbon nanoparticles (NC) in polylactide (PLA) using dichloromethane (DCM) solvent and subsequently, the DCM is evaporated by drying. The electrical conductivity of the composite filament is compared with commercial and academia counterparts. To demonstrate the application of CSMA, three devices /systems are presented in this study. The first one is the actuation of an artificial musculoskeletal (MS) system that can be used as a building block for bioinspired soft robots. The second one is a soft robotic pump inspired by the pumping action of a biological heart. The soft artificial heart can be used in a humanoid robot with facial expressions and can simulate someone blushing or angry by circulating a blood-like fluid. Different designs and their characterization are presented both experimentally and via simulations. The third application is a coronary artery stent. In this work, we performed a case study on the double helix coiled SMA for use as a stent to overcome the mechanical failure due to stress concentration in existing stents. Simulation and experiments were conducted using hyperelastic silicone rubber that mimics the human coronary arteries.



Androids, Shape memory alloys, Nanoparticles, Actuatorspolylactic acid (PLA), fused deposition modeling (FDM) 3D printers

Office of Naval Research (ONR) under the grant number N00014-15-1-2503


©2018 Akshay Potnuru. All rights reserved.