MechE PhD Final Oral Defense: Hun Chan (Bryan) Lee

TITLE: A Soft–Rigid Hybrid Robot for Laser-Assisted Surgery

ABSTRACT: Lasers have become an essential tool in many surgical applications. The unique light absorption property of biological tissue and μm-scale laser spot size enable selective ablation of target tissue. Consequently, these benefits of laser-assisted surgery reduce collateral damage to healthy tissue, shorten recovery time, and minimize the risk of postoperative complications. Yet, manual control of the laser beam still requires a prolonged training period and limits the accuracy of surgery. Further enhancing the outcomes of laser-assisted surgery, robotic technology can improve the precision of laser targeting by enabling automatic closed-loop control. Of robotic technologies, soft robots are well-positioned for delicate surgical environments by providing inherent compliance, flexibility, and robustness. This dissertation focuses on developing a laser steering robot built upon soft robotic technology. To achieve this, two key areas are explored: a soft–rigid hybrid (SHY) robot concept to tackle core challenges in soft robotics, and the design and implementation of a SHY robot tailored for laser-assisted surgery. Some of the key challenges in soft robotics include (1) fabrication inconsistency, (2) scalability, and (3) precise motion controllability. Tackling these challenges, a layer-by-layer fabrication technique is introduced to integrate soft, rigid, flexible, and conductive materials. This strategy builds SHY robots by seamlessly combining a soft-foldable actuator, a proprioceptive sensor, and a mechanical controller into a compact form factor. With these components, SHY robots combine the flexibility and compliance of soft robots and the stability and precise motion control of rigid robots. Additionally, onboard proprioceptive sensors enable real-time shape sensing, which can also be used for feedback control. The versatility of the fabrication and design is demonstrated by introducing robotic modules with mechanically encoded motions and module-assembled continuum robots with various end-effectors. In the final part of this dissertation, a SHY robot for laser-assisted surgery is developed using the aforementioned fabrication method. The primary objective is precise optical-fiber steering via model-free, closed-loop control. Onboard optical sensors provide real-time proprioceptive feedback of the robot’s configuration, and a model-free controller uses this feedback to autonomously track desired trajectories. Feasibility is demonstrated in an in-vitro tissue phantom, where the system reliably guides a simulated laser beam to predefined target locations.

COMMITTEE: ADVISOR Professor Sheila Russo, ME/MSE; CHAIR Professor Douglas Holmes, ME/MSE; Professor William J. Boley, ME/MSE; Professor Andrew Sabelhaus, ME/SE; Professor Loris Fichera, Worcester Polytechnic Institute Robotics Engineering