instruments and the visualization endoscope. Combining multiple instrument controls, drives, and endoscopic visualization into a single-access port requires increased mechanical complexity and density. Notable innovative single-port prototypes include (15, 16). Detached surgical robots The classic laparoscopic paradigm involves elongated instruments each inserted at a pivot point in the abdominal wall through a port/ trocar. This geometry fundamentally constrains the motion by which a surgeon can approach the surgical task. Research to break this constraint faces the challenges of implementing all actuation and sensing inside the body itself, supplying suitable power and communication, and enabling safe deployment and retrieval of an independently deployed robot from the surgical site. Prototypes demonstrating removal of the trocar-pivot constraint include endoscopes and robotic instruments inserted through a port and then attached to the abdominal wall using either magnetic forces (17) or a needle-sized puncture that is also used for power transmission (18). Robots supporting laparoscopic surgery are the most advanced in terms of application to medicine, with more than 5 million people treated, suggesting rapid momentum heading into the next decade. This volume allows medical innovations and the proliferation of new instruments, which are expected to continue. New sensors and better estimation and modeling data and algorithms will allow precise control of force. Gradual introduction of automation to support laparoscopic and other robotic surgeons will allow seamless integration of novel imaging and treatment modes, increasing the surgeon’s role as a supervisor and monitor of advanced surgical instruments. The most important advancements in laparoscopic robotics will be those with the most direct patient benefits, including better treatment of tumor margins with less need to resect healthy tissue, detection and reduction of rare surgical errors, and reduction of trauma and risk of infection from surgical procedures. Nonlaparoscopic procedure–specific robots Inspired by the success of the da Vinci robot for laparoscopic procedures, the past decade has also witnessed surgeons and engineers exploring new robotic solutions for nonlaparoscopic procedures. Key areas of focus have included endoluminal and natural orifice interventions and robots for microsurgery. Endoluminal and natural orifice surgery Of the nascent applications of surgical robots explored in the past decade, we note works on endoluminal and endoscopic robots seeking to further reduce morbidity by eliminating the need for Fig. 3. Medical robotics papers published in engineering and medical journal papers from 1990 to 2020. Curves report paper numbers for hot topics of soft robotics, magnetic actuation, capsule robots, and continuum robots. Note that 2020 publications were potentially reduced by COVID-19 shutdowns (data from Web of Science; see Materials and Methods). Downloaded from https://www.science.org on November 16, 2021 Dupont et al., Sci. Robot. 6, eabi8017 (2021) 10 November 2021 SCIENCE ROBOTICS | REVIEW 6 of 15 skin incisions to access internal anatomy and by offering solutions allowing for deeper access along tortuous anatomical passages. Shang et al. (19) presented a highly articulated endoscopic platform for endoluminal surgery and demonstrated peritoneal cavity and transvaginal access. Burgner et al. (20) explored the potential use of concentric tube robots for transnasal pituitary gland surgery. RiveraSerrano et al. (21) presented the use of a highly articulated robotic probe for transoral access and delivery of manual tools. New commercial systems focused on steerable catheters for natural orifice minimally invasive biopsy also have recently been launched. Perhaps the most notable of these systems are the Ion system by Intuitive Surgical and the Monarch system by Auris Healthcare. The Ion and Monarch systems use dexterous catheter articulation to enable peripheral lung biopsy that would otherwise be very difficult to achieve safely. These systems leverage previously developed modeling and design technology of tendon-actuated continuum robots. Microsurgery Retinal microsurgery poses unique challenges that exceed the capabilities of existing manual surgical systems. Researchers have taken three approaches to addressing these challenges: (i) handheld robots with tremor filtering, (ii) hand-on-hand (cooperative) robots, and (iii) telemanipulated robots with a remote center of motion. Handheld robots with active tremor cancellation have been refined for retinal surgery as in (22). In this approach, the surgeon-produced tremor in the handheld tool is sensed, and a robot at the tip of the tool moves to oppose it such that most of the tremor is canceled out. Cooperative robots provide an alternative approach to tremor suppression while also offering additional capabilities. These robots hold the surgical tool together with the surgeon and operate under admittance control, producing motions based on the forces applied by the surgeon to the tool. The robot’s motions can be more precise than what the clinician can perform freehand and are also tremor free. Furthermore, assistive control laws, based on active constraints/ virtual fixtures, can be implemented to help the