Design optimization and one-shot 3D printing of a bio-inspired soft robot capable of counter-flexural motion at low actuation pressures

This work presents the design, fabrication, and numerical analysis of a soft actuator with counter-flexural motion fabricated in thermoplastic polyurethan (TPU), aiming at mimicking the serpentine movement of snakes. Printing parameters were chosen to allow the one-shot 3D printing of the soft robot, ensuring its air tightness up to 200 [kPa]. The hyperelastic behavior of TPU was characterized by means of uniaxial tensile tests of samples produced with the abovementioned optimal printing settings. Non-linear finite element simulations were conducted to perform a design optimization of the pneumatic chambers; the purpose is to minimize the actuation pressure needed to achieve a prescribed bending. The experimentally measured deflections were compared with numerical results, showing a very good agreement. Practical relapses are in the field of medical devices where the proposed low-pressure actuated design will allow safer human-robot interactions.