Method for Building Self-Folding Machines

Applications

The Inventors have developed a method for building practical and sophisticated self-folding robots to aid in autonomous assembly and manufacturing. The self-folding techniques can be combined with inexpensive planar-fabrication techniques such as lithography, laser-machining, and pick-and-place electrical component assembly machines to quickly produce machines from digital plans.

 

Problem Addressed

Building robots is a time-consuming process in which multiple discrete materials with long assembly times must be assembled sequentially. Attempts to mass-produce robots for efficiency are often infeasible due to the costs of repeated design iterations and optimization steps. In lieu of manual construction, the Inventors have developed a crawling robot that starts as a flat sheet with embedded electronics, and transforms autonomously into a functional machine itself into complex 3D shapes.  The origami-inspired robot can fold itself in four minutes and walk away without human intervention, demonstrating the potential both for complex self-folding machines and autonomous, self-controlled assembly.

 

Technology

The Inventors have developed shape memory composites that fold themselves along embedded hinges. The hinges are controlled by embedded heating elements, and their placement in the composite and the order in which they are triggered create a fold pattern that determines the final shape of the 3D mechanism. The self-folding composite combines a contractile layer or prestretched polystyrene (PSPS) and a passive paper substrate resulting in a bimorph actuator. PSPS is a shape memory polymer (SMP) which is mechanically programmed to contract bidirectionally when heated to approximately 100C. Embedded resistive circuits are included at each hinge as heating elements to enable localized heating and activation of the PSPS. The composite includes PSPS on both sides to enable bidirectional folding. When a contractile layer is activated, it exerts a shear stress on the substrate, causing the composite to fold. Once folding is completed, the hinge is cooled and the PSPS hardens, resulting in a static fold. Self-folding hinges are programmed into the composite with layer-specific features. Passive flexures for dynamic mechanisms are programmed in a similar manner. Not only are flexure joints compatible with folded assembly, they also have operational advantages over typical bearing joints, such as negligible fiction losses and monolithic construction. 

 

Advantages

  • Materials are low-cost and easy to use; straightforward to substitute if needed
  • Assembly method and materials are conducive to rapid construction of robotic mechanisms with minimal human involvement
  • Basic folding patterns can be extrapolated to a wide range of geometries and mechanisms