Continuum robots offer exceptional adaptability and dexterity for tasks in confined and complex spaces. However, their flexible structures inherently limit payload capacity and structural robustness. To overcome this trade-off, many previous studies have proposed variable stiffness continuum robots, but these robots have slow response times that hinder rapid tasks. In this regard, we propose a novel continuum robot with electro-permanent magnet (EPM)-based ball joints. This robot has two key components: an EPM actuator and a variable stiffness ball joint (VSBJ). The EPM-embedded VSBJ constitutes discrete segments of the robot and dynamically transitions between low- and high-stiffness states by controlling the EPM’s magnetic field. This provides the robot with fast-response and variable-stiffness capabilities. In experiments, the VSBJ achieved a 205-fold stiffness variation ratio with a response time of 0.019 s, surpassing the performance of many previously studied robots. Leveraging these capabilities, the proposed robot demonstrated single or multiple bending motions by controlling the stiffness of discrete segments. Finally, the potential of the fast-response variable-stiffness continuum robot for real-world applications was confirmed.

We have developed a two-degree-of-freedom robotic wrist with variable stiffness capability, designed for situations where collisions between the end-effector and the environment are inevitable. To enhance environmental adaptability and prevent physical damage, the wrist can operate in a low-stiffness mode. However, the flexibility of this mode might negatively impact stable and precise manipulation. To address this, we proposed a robotic wrist that switches between a passive low-stiffness mode for environmental adaptation and an active high-stiffness mode for precise manipulation. Initially, we developed a functional prototype that could manually switch between these modes, demonstrating the wrist's passive low-stiffness and active high-stiffness states. This prototype was designed as a lightweight, flat-type modular device, incorporating a sheet-type flexure as the motion guide and embedding all essential components, including actuators, sensors, and a control unit, into the wrist module. Based on the functional prototype, we developed an improved version to enhance durability and functionality. The resulting wrist module incorporates a three-axis force/torque sensor and an impedance control system to control the stiffness. It measures 55 mm in height, weighs 200 g, and offers a 232.4-fold active stiffness variation.

We develop a novel hall-effect-based six-axis force/torque (F/T) tactile sensor integrated into the fingertip of robotic hands. When the robotic hands performs the grasping tasks in an unstructured environment, the visual information plays a main role in sensing the external properties of the objects. However, the various intrinsic properties of the objects such as softness, roughness, mass distribution, and weight cannot be measured properly only with the visual information. To detect the various force information in performing diverse tasks, we aim to implement the six-axis F/T fingertip tactile sensor with hall-effect-based principle. The experimental results demonstrate that the proposed sensor can measure the six-axis F/T with average errors of about 3.3%. In addition, it is observed that the effect of stray field can be shielded by applying a soft magnetic shielding film to the sensor.

We develop a miniature suction-gripper with the goal to realize the novel robotic surgical instrument that can grip slippery and flexible peripheral nerves. In developing the instrument, we place a priority on devising the method that can robustly grip the nerve bundles during the surgical operation for the peripheral nerve. Also, we concentrate to investigate the working principle being able to minimize nerve damages that might be caused when manipulating the nerve. In this study, as the most suitable method to achieve the goal, we scheme to utilize the suction mechanism. Because it can non-invasively grip the nerve based on negative pressure, no external force is applied to the nervous tissues. Therefore the peripheral nerve can be manipulated without serious nerve damage (e.g. crush injury and stretch injury). To improve the gripping ability of the proposed suction gripper, two different types of microneedle arrays are applied to the suction-tips: passive-microneedle (PMN) arrays and active-microneedle (AMN) arrays. Since the most outer membrane of the nerve can be anchored by the penetrated PMN and AMN, the gripper can grip the nerve more robustly. The designed suction-gripper is fabricated as a functional prototype, and its working performances are assessed with in-vitro and in-vivo animal experiments. The experimental results well demonstrate the practical effectiveness of the proposed method and its applicability to the neurosurgical robot for the peripheral nerve.

We develop a novel cube-shaped finger-wearable haptic interface named as HaptiCube. With the aim of implementing the tactile device with improved functionality and wearability, we focus on designing the device to have two characteristics: multi-DOF force feedback displayability and large force capability with compact and lightweight structure. In designing the device, we mainly consider the type and configuration of actuator and driving mechanism, since both have a great effect on the size, weight, and output force of the device. As the actuator, we select the shape memory alloy exhibiting high energy density. And, as the driving mechanism, two different types of compliant mechanism are designed for two important functions: to convert contraction of the SMA to the desired motion as a motion guide and to apply bias-force to the SMA as a bias-spring. The device is designed as the miniature interface that can display 3-DOF pressure and 2-DOF shearing force to user's fingerpad. And, it is implemented as the functional prototype with the total weight of 26 g including actuators and all mechanical components. The experimental results on working performances (e.g. stroke, output force, and bandwidth) demonstrate that the device has superiority in terms of multi-DOF displayability, compact-sizability and wearability.

This paper presents preliminary results of a handheld device to assist the insertion of intra-fascicular planar electrodes into a peripheral nervous system. The developed device consists of two units, a nerve holder and an electrode inserter. We introduce design considerations, features, and underlying mechanisms of the device. User tests and animal experiments show that users can easily and accurately adjust the insertion position and direction of nerve electrodes while manipulating the device in 3D, and that planar electrodes are successfully inserted into sciatic nerves of rats. We hope that the proposed device will help neural engineering researchers and scientists to simplify the surgical process and produce consistent experimental results.