Jeongryul Kim

Accurate nasopharyngeal specimen collection requires defining an appropriate insertion path, which is challenging under patient-specific facial anatomy and limited observation conditions. To address these challenges, this study presents an automated robotic framework that focuses on defining a patient-specific insertion path prior to the insertion process. The system uses an RGB-D camera and a deep learning model, EarPointNet, to detect facial landmarks, estimate the ear canal location, and compute a patient-specific insertion direction toward the nostril based on guidelines from the U.S. Centers for Disease Control and Prevention. EarPointNet achieved angular errors between 2.33° and 3.68° on an optimized dataset. Repeatability was further evaluated through comparative experiments with non-expert manual operation using a medical phantom. Additional experiments examined path estimation performance under partially occluded facial conditions with varying face-hole sizes, maintaining a mean angular error of 2.62° with a face hole radius of 100 mm. Future work will focus on integrating force sensing, torque sensing and reactive safety control, as well as conducting clinician-involved validation toward medical certification.

In collaborative robotics, achieving high-speed yet safe object handover remains a key challenge. Rigid grippers pose impact risks to humans, whereas compliant grippers compromise grip stiffness and positional accuracy. This paper presents the three-finger rapid variable-stiffness gripper (RVSG), which modulates grip stiffness within one second through a simplified hardware mechanism by adjusting only the elastic cable initial tension T₀ and the finger spacing w₁. Based on a simplified model, the variation in gripper stiffness was simulated by tuning T₀ and w₁, and subsequently validated with a prototype implementation. By adjusting these two parameters, the prototype attains a variable stiffness range of 12.25 to 75.33 N/m, corresponding to a relative stiffness variation efficiency of 615%. Collision safety tests measured contact forces between 0.17 and 1.01 N, representing a 92.5 to 98.7% reduction compared to commercial rigid grippers. These results demonstrate a lightweight, low-complexity solution for fast and safe human-robot handovers, with potential applications in assembly, logistics, and surgical assistance. Future work will extend the approach to three-axis stiffness control and develop higher-order models that incorporate friction and effective contact distance.

Minimally invasive surgery (MIS) using robots minimizes patient injury but is challenging due to reduced bending force in smaller-diameter tools. Lowering the bending resistance of actuating cables is critical, particularly when tool diameters are small and cable tension is limited. Traditional methods rely on costly, low-resistance materials. This study proposes a cost-effective design using multiple thin stainless-steel cables and cable slots instead of single cables and conventional cable holes. To optimize the proposed multi-cable design, simulations and polynomial regression were employed to determine the ideal slot dimensions, focusing on reducing bending resistance. Kinematic analysis and experiments confirmed reduced bending resistance in multi-cable designs. A 3 mm prototype showed 25% higher bending force and 63% increased bending distance under a 1.196 N payload compared to single-cable mechanisms. Circular trajectory experiments demonstrated improved accuracy and reduced velocity variation. A prototype successfully excised a tumor from a BALB/c mouse, verifying sufficient force for surgical tasks. Future work will address assembly challenges and explore cable arrangement effects on bending force and hysteresis.

Hyper-redundant manipulators are widely used in minimally invasive surgery because they can navigate through narrow passages in passive compliance with the human body. Although their stability and dexterity have been significantly improved over the years, we need manipulators that can bend with appropriate curvatures and adapt to complex environments. This paper proposes a design principle for a manipulator capable of adjusting its non-uniform curvature and predicting the bending shape. Rigid segments were serially stacked, and elastic fixtures in the form of flat springs were arranged between hinged-slide joint segments. A manipulator with a diameter of 4.5 mm and a length of 28 mm had been fabricated. A model was established to predict the bending shape through minimum potential energy theory, kinematics, and measured stiffnesses of the flat springs. A comparison of the simulation and experimental results indicated an average position error of 3.82% of the endpoints when compared to the total length. With this modification, the manipulator is expected to be widely used in various fields such as small endoscope systems and single-port robot systems.

Background: Curved surgical instruments are being developed to expand the workspace of straight surgical instruments. They are required to have a small diameter and high stiffness.Methods: We developed a double‐spring pre‐curved cannula (DSPC) for electrocauterization, which has curved movements controlled solely by translational motion, and high stiffness via wire tension. It comprises a straight extension spring, pre‐curved flat spring and braided high‐modulus polyethylene line. A handheld device was designed for intuitive DSPC manipulation. The cannula has a 3.9 mm diameter and serves as a protective tube such that the electrode can safely reach the lesion.Results: Experimental results demonstrate that the DSPC has ideal curvature and maximum stiffness of 1.38 N/mm. In a cadaveric study, the DSPC reached the inferior glenohumeral ligament, which conventional surgical instruments cannot access, and surgeons successfully performed electrocauterization.Conclusions: The designed DSPC is effective for future use in forceps, curettes and surgical robots.

This paper describes a surgical device that uses a compensation mechanism without motors and electronics to reduce the backlash in the end-effector. The device improves the precision and accuracy of surgical operations that involve unpredictable curved paths at a low cost. The device includes a flexible tube that moves along a curved path and a mechanism that compensates for the change in the length of the wire that actuates the end-effector as it follows an unpredictable path. The compensation mechanism minimizes the wire slack by utilizing a slider and spring mechanism that can maintain the pull wire length but can also move freely to extend the wire length as needed. We maximized the compensable wire length by optimizing the device driving parameters via simulation, verified the device performance experimentally, and built a fully operational prototype. The backlash of the device end-effector was reduced by approximately 38.3% compared to a device without compensation. Surgeons used the prototype with animal models in vivo and evaluated it as convenient and easy to manipulate. A hand-held non-robotic surgical device that compensates for wire length in unexpected curved paths to reduce end-effector backlash was demonstrated. The performance of the prototype was validated by driving, backlash, and hysteresis measurements, and in vivo animal experiments. This study is a significant step towards the development of a high-precision and low-cost surgical device for use in deep and narrow anatomies with unpredictable curved paths.

Hyper-redundantmanipulators (HRMs) are widely used in minimally invasive surgery (MIS) because of their flexibility, dexterity, and compactness. However, when an external load acts on an HRM, its bending motion is disturbed and the workspace decreases. In addition, the external load increases the cable tension, and thin cables may break due to their low breaking strengths. This article proposes a cable-movable rolling joint that increases the workspace for MIS under an external load and reduces the actuating cable tension through cable movement. Furthermore, it presents an optimized motion estimation analysis method that verifies the manipulator performance by finding the equilibrium position and predicting the shape and tip position. The simulated manipulator exhibited a shape similar to that of the prototype and an average tip position difference of 4.59% based on the prototype length. Under an external load of 150 g, the workspace and cable tension of the prototype were 27.32% larger and 1.79 N lower than those of the conventional rolling joint, respectively. The new cable-movable mechanism and estimation analysis method will help improve the bending performance and position accuracy of HRMs for MIS.

Background: Microsurgery is generally performed in narrow spaces with limited movement. Endoscopes that allow for angle changes have been developed using elastic materials, but they require a large bending space. We propose a new endoscope with a small sweep volume for angle changes. Methods: We fabricated a prototype with a thumb-operated joystick. The image sensor is attached to the tooltip. The image signal is input to a motor control board which computes inverse kinematics and transforms it into joint angle values. Each axis is positioned according to these values. Results: The tooltip sweeping volume was 104 mm(3). Surgeons at the Asan Medical Center used our endoscope to obtain images of the biceps tendon and subscapularis joints of a cadaver. Conclusion: Currently, a low-resolution image sensor is attached to endoscope tooltips. In the future, we will develop a high-resolution image module equipped with an ultra-small complementary metal oxide semiconductor sensor.