Figs. 2 and 3 differ by an order of magnitude. 1 Department of Cardiovascular Surgery, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA. 2 Institute of Robotics and Intelligent Systems, Department of Mechanical and Process Engineering, ETH-Zürich, Zürich, Switzerland. 3 Department of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235, USA. 4 Department of Electrical and Computer Engineering, University of Washington, Seattle, WA 98195, USA. 5 Biorobotics Institute, Scuola Superiore Sant'anna, Pisa, Italy. 6 Department of Mechanical Engineering, Rice University, Houston, TX 77005, USA. 7 Department of Electronic and Electrical Engineering, University of Leeds, Leeds, UK. 8 Medical Robotics Institute, Shanghai Jiao Tong University, Shanghai, China. *Corresponding author. Email: pierre.dupont@childrens.harvard.edu Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works Downloaded from https://www.science.org on November 16, 2021 Dupont et al., Sci. Robot. 6, eabi8017 (2021) 10 November 2021 SCIENCE ROBOTICS | REVIEW 2 of 15 From Fig. 2, the number of publications on medical robotics in engineering and medical journals has grown exponentially from a total of 6 in 1990 to more than 3500 in 2020. Medical journal papers are dominated by publications on laparoscopic robots (60 to 70% of total) with more than 1300 published in 2020 owing to the success of Intuitive Surgical’s da Vinci robot. In line with the maturity of this technology, engineering papers on laparoscopy, in contrast, peak at 126 in 2019. Engineering papers are dominated by therapeutic rehabilitation and assistive wearable robots. This pair of hot topics represents about 80% of the engineering-journal medical robotics papers published over the past decade. Although these two topics entered the decade with an equal number of papers, therapeutic rehabilitation has subsequently notably outpaced assistive wearable robots. It is interesting to note, however, that the number of medical papers on these topics is less than 25% of the number of engineering papers. This is likely due to the fact that medical journal papers often report the results of clinical trials, which are much more costly and time consuming to perform than engineering studies. The technologies plotted in Fig. 3 are less mature than those of Fig. 2 and consequently are the subject of fewer engineering and medical journal papers. Of these, magnetic actuation is the most mature, and exponential growth in both engineering and medical papers can be observed, with medical papers lagging engineering papers. Continued growth of this topic to some extent hinges on whether clinically viable applications of microrobots can be developed. The plots of soft robotics papers show this topic to be early in its development cycle. It should be noted, however, that we excluded the large numbers of fundamental articles on soft actuators and sensors appearing in materials journals that suggest medical robotics as a potential application. The mapping of these broadly applicable technologies into medical robots over the next decade will likely produce the exponential growth suggested by the curves in Fig. 3. Continuum robot technology is unusual in that manually actuated continuum-style medical instruments existed long before 1990. While new continuum robot architectures have been developed in recent decades, the critical advance to make these devices robotic was not one of mechanical design but rather of mathematical modeling. This work is largely complete as described in its hot topic section below, and future growth in engineering papers will likely describe clinical robot designs incorporating continuum components. Medical papers on this topic have been slow to take off because commercial efforts, e.g., Hansen Medical’s cardiac ablation catheters, have been unsuccessful. New clinical systems—such as Intuitive Surgical’s Ion robot and Auris Healthcare’s Monarch platform (the latter based on Hansen Medical’s robotic catheter technology), both for performing distal lung biopsies—will lead to increasing numbers of medical papers in the coming decade. Capsule robots are the least mature and perhaps the most specialized of the hot topic technologies. Their capabilities, as reported in the publications of Fig. 3, have improved substantially over the past decade. This technology may be at an inflection point. If the capabilities of these robots can be proven sufficient to displace current clinical approaches, then interest in this topic will accelerate, enabling its further development. There is some evidence that this is the case for soft capsule robots under magnetic actuation, an approach that has potential for noninvasive diagnosis and therapy inside the digestive tract. The following sections describe each hot topic, provide a summary of the most important accomplishments over the decade, and include insights on current and future research directions. As represented in Figs. 2 and 3, many papers have been published on each topic. With the goal of highlighting a focused reading list for readers who wish to most rapidly come up to speed on a topic, only a few highly cited papers are provided as