Uikyum Kim

A transparent and stretchable graphene-based actuator for tactile display

A tactile display is an important tool to help humans interact with machines by using touch. In this paper, we present a transparent and stretchable graphene-based actuator for advanced tactile displays. The proposed actuator is composed of transparent and compliant graphene electrodes and a dielectric elastomer substrate. Since the electrode is coated onto the appointed region of the substrate layer by layer, only the area of the dielectric elastomer substrate with electrodes bumps up in response to the input voltage, which consequently produces actuation. The actuator is proven to be operable while preserving its electrical and mechanical properties even under 25% stretching. Also, the simple fabrication of the proposed actuator is cost-effective and can easily be extended to multiple arrays. The actuator is expected to be applicable to various applications including tactile displays, vari-focal lenses etc.

Force Sensor Integrated Surgical Forceps for Minimally Invasive Robotic Surgery

This paper presents a novel surgical instrument integrated with a four-degree-of-freedom (DOF) force sensor. By adopting the capacitive transduction principle, the sensor enables the direct sensing of normal and shear forces at surgical instrument tips. Thus, three-DOF pulling forces and a single-DOF grasping force can be measured for haptic feedback control of robotic minimally invasive surgery systems. The sensor consists of four capacitive transducers, and all the transducers including analog signal processing units are embedded in small surgical instrument tips. The four-DOF force sensing is enabled thanks to the four capacitive transducers by using the force transformation method. In this study, the instrument is designed and manufactured to be adaptable to the open-source surgical robot platform, called Raven-II. In addition, the sensing system is experimentally validated through its application to the Raven-II by using a reference force sensor.

A small biomimetic quadruped robot driven by multistacked dielectric elastomer actuators

A kind of dielectric elastomer (DE) material, called ‘synthetic elastomer’, has been developed based on acrylonitrile butadiene rubber (NBR) to be used as a dielectric elastomer actuator (DEA). By stacking single layers of synthetic elastomer, a linear actuator, called a multistacked actuator, is produced, and used by mechatronic and robotic systems to generate linear motion. In this paper, we demonstrate the application of the multistacked dielectric elastomer actuator in a biomimetic legged robot. A miniature robot driven by a biomimetic actuation system with four 2-DOF (two-degree-of-freedom) legged mechanisms is realized. Based on the experimental results, we evaluate the performance of the proposed robot and validate the feasibility of the multistacked actuator in a locomotion system as a replacement for conventional actuators.

A Laparoscopic Grasping Tool With Force Sensing Capability

This paper presents a laparoscopic grasping tool for minimally invasive surgery with the capability of multiaxis force sensing. The tool is able to sense three-axis Cartesian manipulation force and a single-axis grasping force. The forces are measured by a wrist force sensor located at the distal end of the tool, and two torque sensors at the tool base, respectively. We propose an innovative design of a miniature force sensor achieving structural simplicity and potential cost effectiveness. A prototype is manufactured and experiments are conducted in a simulated surgical environment by using an open platform for surgical robot research, called Raven-II.

A Capacitive-Type Novel Six-Axis Force/Torque Sensor for Robotic Applications

This paper presents an innovative design of a six-axis force/torque sensor, which enables ease of manufacturing, cost reduction, and ruggedness in operation. The advantages are realized by simplifying the structure of the sensor and reducing manual labor during the manufacturing process. In order to achieve a simple sensor structure, we propose a capacitive-type force sensing scheme in which the sensing elements are aligned in-plane. By using this method, all the sensing elements can be fabricated on single printed circuit board, and thus, manual tasks, such as bonding and coating the sensing elements, can be eliminated. In order to verify the feasibility of the idea, a prototype six-axis force/torque sensor was manufactured, and its performances were evaluated. The characteristics of the prototype are analyzed in terms of condition number, static response, time domain response, hysteresis, repeatability, and time drift.

A Novel Six-Axis Force/Torque Sensor for Robotic Applications

This paper presents a novel six-axis force/torque (F/T) sensor for robotic applications that is self-contained, rugged, and inexpensive. Six capacitive sensor cells are adopted to detect three normal and three shear forces. Six sensor cell readings are converted to F/T information via calibrations and transformation. To simplify the manufacturing processes, a sensor design with parallel and orthogonal arrangements of sensing cells is proposed, which achieves the large improvement of the sensitivity. Also, the signal processing is realized with a single printed circuit board and a ground plate, and thus, we make it possible to build a lightweight six-axis F/T sensor with simple manufacturing processes at extremely low cost. The sensor is manufactured and its performances are validated by comparing them with a commercial six-axis F/T sensor.

Printable monolithic hexapod robot driven by soft actuator

Aiming to apply soft actuators in driving a walking robot, the design, fabrication and locomotion of a bio-inspired printable hexapod robot are studied. The robot mimics the insects design and walking posture by driving six legs with alternating tripod gait which provides its locomotive adaptability on flat terrains. The versatile movements of the robots leg are achieved by using soft and multiple degree-of-freedom actuators. The actuators are made by dielectric elastomers with a simple mechanism based on antagonistic configuration. By using 3D printing method, the actuator can be embedded into the frame of the robot and a control system is developed. Finally, the robots locomotion is successfully demonstrated with variable speeds and stride lengths.

Preliminary design of multi-axial contact force sensor for minimally invasive robotic surgery grasper

This paper presents a preliminary design and experimental results of a multi-axial contact force sensor for robotic surgery graspers. The sensor is a thin-film type capacitive one with a multiple cell structure capable of measuring normal and shear forces at contacts simultaneously. The structure of the sensor is determined via numerical optimization for maximizing sensitivity and based on the results, a prototype is fabricated by employing the silk-screening method. The characteristics of the sensor are evaluated with a multi-axial sensor calibration set-up and the sensitivities for two directional shear forces and a normal forces are measured to be 10.1, 10.3 and 6.1%, respectively. In this study, the feasibility of the sensor is confirmed as the proof-of-concept. In our future studies, a miniaturized pair of the proposed sensor will be embedded to a surgery grasper for in vitro validation.

Design and realization of grasper-integrated force sensor for minimally invasive robotic surgery

This paper presents a grasper-integrated force sensor that provides the capability of measuring dual axial forces at the tip of surgical robot for minimally invasive surgery (MIS). On the sensorized forceps, the combination of dual axial forces measured at each side of grasper presents three axial pulling and single axial grasping force sensing, which provide force feedback control using haptic device. It consists of simple structure of triangular prism shape and two capacitive-type pressure sensor cells based on elastomeric polymer which provides the information on normal and shear forces. The sensing principle is to compare the difference between responses of two pressure sensors when the surface of the sensor contacts to the tissue. A sensorized forceps is fabricated by employing the molding method and electronics for signal processing is embedded. Finally, experimental evaluations are performed and its feasibility is validated.

Six-axis capacitive force/torque sensor based on dielectric elastomer

The six axis F/T sensor is a primary component for the robotic technologies, but its high unit cost hampers the popularization to the robotic applications. In this paper, we present a six-axis force-torque capacitive sensor based on dielectric elastomer. Dielectric elastomer is compressed and deformed with external forces acting on it. Its deformation results in the variation of capacitance, which can be used as a kind of capacitive sensing scheme. The proposed sensor consists of plastic structure and dielectric elastomer capacitors. Since it takes a simple structure, it is possible to fabricate by using a plastic molding process, which results in extremely lower cost than existing off-the-shelf products. We present the basic structure and design of the sensor with the explanation of its working principle. A fabrication method dedicated to the sensor is developed and finally, a prototype will be demonstrated with calibration procedures.