Microsurgical Devices by Pop-up Book Mems

The small scale of microsurgery poses significant challenges for developing robust and dexterous tools to grip, cut, and join sub-millimeter structures such as vessels and nerves. The main limitation is that traditional manufacturing techniques are not optimized to create smart, articulating structures in the 0.1 – 10 mm scale. Pop-up book MEMS is a new fabrication technology that promises to overcome this challenge and enable the monolithic fabrication of complex, articulated structures with an extensive catalog of materials, embedded electrical components, and automated assembly with feature sizes down to 20 microns. In this paper, we demonstrate a proof-of-concept microsurgical gripper and evaluate its performance at the component and device level to characterize its strength and robustness. 1-DOF Flexible hinge joints that constrain motion and allow for out-of-plane actuation were found to resist torsional loads of 22.8±2.15 N·mm per mm of hinge width. Adhesive lap joints that join individual layers in the laminate structure demonstrated a shear strength of 26.8±0.53 N/mm. The laminate structures were also shown to resist peel loads of 0.72±0.10 N/mm. Various flexible hinge and adhesive lap components were then designed into an 11layered structure which ‘pops up’ to realize an articulating microsurgical gripper that includes a cable-driven mechanism for gripping actuation and a flexural return spring to passively open the gripper. The gripper prototype, with final weight of 200 mg, overall footprint of 18 mm by 7.5 mm, and features as small as 200 microns, is able to deftly manipulate objects 100 times is own weight at the required scale, thus demonstrating its potential for use in microsurgery. INTRODUCTION Small joint surgery, such as that in the wrist or fingers, presents a number of significant challenges due to the limited maneuverable workspace and the presence of many delicate structures that must be avoided, including sensitive cartilage surfaces and tendons [1]. Current commercial small-joint surgical instruments are limited to straight, simple tools without any distal articulation which would allow for greater access and dexterity inside the joint [2]. In addition, the robust electromechanical surgical tools at the sub-mm scales required for these procedures are either impossible or commercially impractical to make with existing manufacturing techniques such as surface/bulk micromachining [3], wire-EDM [4], microinjection molding, or micromilling/lathing [5]. It is our goal to apply an emerging micromachining and assembly technique that we have developed to enable robust, dexterous, and practical microsurgical instruments for small joint repair. We have developed a novel micro-manufacturing technique known as Pop-Up Book MEMS (‘Pop-Ups’) that allows for the fabrication of complex, multi-functional electromechanical devices on the 0.1-10 mm scale [6] [7]. Pop-Up technology enables the ability to create 3-D, multi-material, monolithic meso and micro-structures using purely 2-D planar