MR-Conditional SMA-Based Origami Joint

Foldable origami structures have been implemented into robotics as a way of compacting joints and circuitry into smaller structures. This technique is especially useful in minimally invasive surgical instruments, where the goal is to create slimline devices that can be inserted through small incisions. Origami also has the potential to cut costs by reducing the amount of material required for assembly. Origami devices are especially suitable for magnetic resonance imaging (MRI)-guided procedures, where instruments must be nonmagnetic because origami is more suitable for flexible, nonmetallic materials. MR conditional surgical instruments enable intraoperative MRI procedures that provide superior imaging capabilities to physicians to allow for safer procedures. This work presents an MR conditional joint developed using origami techniques that reduces costs by eliminating assembly of various components and has potential applications in endoscopy. The joint is a compliant rolling-contact element that employs curved-folding origami techniques. A chain of these joints can be constructed from a single sheet of material, eliminating assembly of numerous materials to produce a final product, which is specifically advantageous for constructing low-cost, disposable surgical devices. The prototype contains a degree of bending of ±9° per joint and an actuation force of 0.5 N using a 1.25 A current. The MRI results showed a minimal artifact of less than 1 mm measured from the boundary of the joint chain and a signal-to-noise ratio reduction of less than 10%.