OctoGrasp: The Design and Construction of a Cephalopod-Inspired Prosthetic Arm

Overview

Purpose The purpose of the OctoGrasp project is to design and build a highly dexterous bio-mimetic prosthetic arm inspired by the biology of cephalopods. Typical prosthetics rely on force at the fingertips to pick up objects using bulky, high-torque motors. Instead of relying entirely on mechanics, the OctoGrasp employs negative pressure pneumatics that can manipulate objects through suction. The measure of success for the OctoGrasp hand is the ability to replicate the 33 commonly-used grips described in the Human Grasping Database. An additional constraint is that the OctoGrasp hand should be light enough not to impair the movement of the user. Finally, a typical prosthetic can cost tens of thousands of dollars and require complex manufacturing techniques. This project intends to create an affordable (~$100) prosthetic that is easy to manufacture and assemble. Design Process The design of the OctoGrasp hand involved many iterations across the design of the fingers, palm, thumb, and arm. The fingers were initially constructed using CNC milled pieces of polycarbonate, a material chosen for its strong and tough properties. Two polycarbonate design iterations were constructed before switching to Thermoplastic Polyurethane (TPU), a material chosen for its flexible and 3D-printable qualities. A total of seven distinct finger prototypes were designed and created. Designing the palm required the use of complicated CAD techniques such as loft features and guide curves. A total of seven prototype designs were made, starting with the general shape of a palm and adding space for a thumb later. Initially, the arm housed the servo motors, but to save space the servos were moved into the back side of the palm. The arm houses the electronics, pumps, and solenoids. Results The OctoGrasp is able to reach all 33 of the grips in the Human Grasping Database, using a combination of mechanical motion and negative pressure pneumatics. On average, OctoGrasp outperformed its competitors in grasp speed by 3.5x (430 ms vs. 1540 ms). The OctoGrasp costs only $111.57 to assemble. It is 90x cheaper than its closest competitors, which are priced at $10,000 or above. The OctoGrasp has an average of 1.8x the Degrees of Freedom (DoF) compared to its competitors (6 DoF vs 3.3 DoF). Conclusions The OctoGrasp project presents a novel, inexpensive, and practical approach to prosthetics. The device takes inspiration from the biology of cephalopods in order to create a more efficient prosthetic. Link to project write-up: https://docs.google.com/document/d/1uuy5zF5Y4zUsvXOxoK7ICSyHkoB_aciHa_SiirPIsuo/

Awards (1)

• Category Award: 2

Competition history

• CSEF 2023 Electronics & Electromagnetics · Entry S1011

Resources

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