Laser Cutting as a Rapid Method for Fabricating Thin Soft Pneumatic Actuators and Robots

Abstract

Pneumatically actuated soft robots address many challenges with interfacing with delicate objects, but these actuators/robots are still bulky and require many hours to fabricate, limiting their widespread use. This article reports a novel design and manufacturing method for ultrathin soft robots and actuators (∼70 μm) using a laser-cutting machine that cuts/welds sheets of thermoplastic polyurethane (TPU) from a 2D CAD drawing. Using this method, five different soft actuators (e.g., bending, rotating, contracting) are designed, fabricated, and characterized with both planar and nonplanar motions. Furthermore, we show how stacking multiple sheets of TPU enables rapid fabrication of multifunctional actuators. Finally, a portable four-arm swimming robot is designed and fabricated without any assembly steps. This rapid fabrication method enables soft robots to go from concept to operational within minutes, and creates a new subclass of soft robots suitable for applications requiring a robot to be ultrathin, lightweight, and/or fit within small volumes.

Keywords: laser cutter; rapid fabrication; soft robotics; thermoplastic polyurethane; thin pneumatic actuators.

FIG. 1.

Fabrication process. (a) Four layers of thermoplastic polyurethane are heat pressed to conformal contact. (b) A laser beam cuts the layers with a desired pattern. (c) The inflated chamber is bounded by one and three layers on its sides; the asymmetry of the stiffness leads to a bending motion. Color images available online at www.liebertpub.com/soro

FIG. 2.

Bending actuator type I. (a) Sequence of images showing the bending motion of actuator type I. (b) Comparing the ultimate bending configuration of the actuator with that of FEM simulation. (c) Comparison between the simulated and experimental lateral displacements of the thin ACTUATOR. FEM, finite element method. Color images available online at www.liebertpub.com/soro

FIG. 3.

Bending actuator type II. (a) Asymmetric 2D profile for actuator type II. (b) Sequence of images showing the bending motion of actuator type II. (c) Comparing the ultimate bending configuration of the actuator with that of FEM simulation. (d) Comparison between simulated and experimental lateral displacements of the thin ACTUATOR. Color images available online at www.liebertpub.com/soro

FIG. 4.

Other types of actuators. (a) Schematic and prototype of a rotary actuator (300° rotation). (b) Schematic unit cell and prototype of an axial actuator (unactuated and actuated states). (c) Schematic and prototype of a biaxial actuator (unactuated and actuated states). Color images available online at www.liebertpub.com/soro

FIG. 5.

Development of a soft gripper. (a) Schematic of a bidirectional soft actuator and design of its working principle. (b) Images of the unactuated, open, and close configurations for this thin ACTUATOR. (c) Images depicting how these different configurations grasp objects for the pick-and-place task. CW, clockwise; CCW, counterclockwise. Color images available online at www.liebertpub.com/soro

FIG. 6.

Development of a swimming robot. (a) Schematic design of swimming robot for generating forward swimming motions. (b, c) Unactuated and actuated configurations in forward motion mode. Color images available online at www.liebertpub.com/soro

FIG. 7.

Analysis of swimming motion. (a) Sequence of swimming motion for one cycle. (b) Pressure inside the robot during the inflation and deflation periods. (c) Horizontal displacement of robot during the inflation and deflation phases. (d) Total displacement after seven cycles (14 s). Color images available online at www.liebertpub.com/soro