Snap-On Robotic Wrist Module for Enhanced Dexterity in Endoscopic Surgery* Joshua Gafford, Student Member, IEEE, Tommaso Ranzani, Sheila Russo, Dr. Hiroyuki Aihara, Dr. Christopher Thompson, Robert Wood, Member, IEEE, Conor Walsh, Member, IEEE Abstract—Burgeoning transendoscopic procedures, such as endoscopic submucosal dissection (ESD), provide a promising means of treating early-stage gastric neoplasia in a minimally- invasive way. However, the remote locations of these lesions, coupled with their origination in the submucosal layers of the gastrointestinal tract, often lead to extreme technical, cogni- tive and ergonomic challenges which combat the widespread applicability and adoption of these techniques. Among these challenges is achieving the in vivo dexterity required to retract and dissect tissue. By leveraging workspace and force data obtained through clinical studies, we developed a modular, disposable, distally-mounted actuator (an ‘active endcap’) that can augment an endoscopist’s distal dexterity in ways that are not achievable with the endoscope’s built-in degrees-of-freedom. The device consists of a flexible articulating ‘exoskeleton’ manu- factured via printed-circuit MEMS (PCMEMS) which engages and deflects electrosurgical tools that are passed through the endoscopic working channel. Embedded proprioceptive sensing is implemented on-board using distributed LED/phototransistor pairs and the principle of light intensity modulation (LIM). The distal degree-of-freedom is actuated using shape memory alloy (SMA) technology, and the actuation transmission system is fully contained within a 1-inch-long end cap that can be mounted on the distal end of the endoscope, thereby obviating the need for a mechanical connection to a proximal source. Proof-of-concept tests demonstrate that the actuator adds over 50 degrees of distal articulation to existing tools and can generate 450 mN of lateral force which has been clinically determined to be sufficient for performing circumferential incisions in ESD. I. I NTRODUCTION Innovation in robotic surgery is seeing a paradigm shift from rigid, teleoperative serial manipulators to flexible co- robotic tools capable of accessing remote locations inside *This material based on work supported by Defense Advanced Research Projects Agency (DARPA), A2P (Grant No. FA8650-15-C-7548). This work was also partially funded by the Wyss Institute for Biologically Inspired Engineering and the John A. Paulson School of Engineering and Applied Sciences at Harvard University. J. Gafford is with the John A. Paulson School of Engineering and Applied Sciences at Harvard University, Cambridge, MA 02138 USA (jgafford@seas.harvard.edu). T. Ranzani and S. Russo are with the John A. Paulson School of Engi- neering and Applied Sciences, Harvard University, Cambridge, MA 02138 USA, and the Wyss Institute for Biologically-Inspired Engineering, Harvard University, Boston, MA 02115 USA (tranzani, srusso@seas.harvard.edu). H. Aihara and C. Thompson are with Brigham and Women’s Hospital, Boston, MA 02115 USA (haihara, ccthompson@partners.org). R. Wood and C. Walsh (corresponding author) are with the Faculty of the John A. Paulson School of Engineering and Applied Sciences at Harvard University, Cambridge, MA 02138 USA, and the Wyss Institute for Biologically-Inspired Engineering, Harvard University, Boston, MA 02115 USA (rwood, walsh@seas.harvard.edu). Elastic Flexure SMA Actuation Fig. 1: Rendering of a distally-actuated 1 DoF modular wrist with callouts to important features. An articulating module interfaces with and deflects existing electrosurgical tools passed through the endoscope working port. the body [1]–[5]. This paradigm shift is concurrent with a desire to perform ‘scarless’ surgery through natural orifices to substantially reduce morbidity and recovery. While a number of systems have demonstrated unparalleled dexterity in nav- igating the body’s tortuous anatomy, limited sophistication in end-effector design has severely impeded the therapeutic applications of these systems. To usher in the next generation of therapeutic endoscopic tools, it is of paramount importance to develop sophisticated end-effector morphologies that can extend the capabilities of these systems. General trends in surgical endoscopy have pointed to- wards minimally-invasive applications in both diagnostic and therapeutic interventions that were previously impossible to perform. A burgeoning transendoscopic technique called endoscopic submucosal dissection (ESD) is being seen as a promising means of removing early-stage gastric neoplasia in a minimally-invasive way [6]. The technique involves the insertion of an endoscope or gastroscope through the mouth, navigating to the site of the tumor, and using a combination of forward-cutting and side-cutting bipolar cautery to resect and remove the diseased tissue from the submucosal space. Due to the technical and cognitive complexity involved, coupled with a reliance on surgical devices that are ill-suited for the task at hand, ESD has seen limited penetration into clinical practice. In addition, the unintuitive mapping between the endoscope controls and the distal dexterity required at the tip make ESD a prime candidate for robotic innovation. 2016 IEEE/RSJ International Conference on Robotics and Automation (ICRA) May 16-21, 2016, Stockholm, Sweden.