A Novel fabrication method for rapid prototyping of soft structures with embedded pneumatic channels

Abstract

Soft robotics is a major disruptive technology that is rapidly revolutionizing the world of robotics. As the design optimization of these soft robotic structures are still in its infancy, their designers have to resort to prototype testing. This paper describes how a novel casting method based on a 2D layered approach and thermal programming of pneumatic tubing can be used to simplify soft structure prototyping. The proposed casting method is based on the sequential stacking of laser-cut pre-fabricated plates, i.e. PMMA (acrylic) sheets, to create a 3D mold, instead of the traditional methods of fabricating 3D molds, such as CNC machining or 3D printing. Contemporary soft robotic applications are more interested in pneumatic actuation and thus require pneumatic channels embedded within their structure. Creation of channels is a critical factor that limit the fabrication scope of most such soft structures. A simple solution is using Polyurethane (PU) tubing to create channels within soft structures. A limitation of PU tubes is that, they cannot be directly embedded as any twist added to obtain the required path of the tube adds a strain on the soft structure from within, which can affect the desired operation. Hence, the authors propose removing the strain on the PU tubes by thermally programming the required shape onto the PU tube. PU tubes reinforced with copper cores are bent in to the desired shape and are heat treated to program the desired shape. After placing the programmed tubes within the mold, silicon rubber can be simply poured into the mold; and the finished structure can be taken out of the mold once cured. Main purpose of this paper is to present these two novel fabrication methods to simplify soft robotic prototyping, without the need for advanced, costly, complex equipment.