Choonghan Lee

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.

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.

Enhancement of transduction performance of a dielectric elastomer actuator based on acrylonitrile butadiene rubber

AbstractThe synthetic elastomer based on acrylonitrile butadiene rubber (NBR) has been recently developed as a kind of dielectric elastomer actuators (DEAs). Its advantages are that its properties can be modified according to the requirements of applications. In this paper, we report a comprehensive study on the effects of plasticizers including diisodecyl phthalate (DIDP), dioctyladipate (DOA), and dioctyl phthalate (DOP) as well as a high dielectric additive, which is, barium titanate (BaTiO3) with respect to the overall performance of the synthetic elastomer. We investigate how the significant parameters representing the actuator performance can be changed according to the composition of the additives and how the actuation performances can be improved. In addition, we address how the environmental conditions such as exposure to the light and the air have influence on the properties of the synthetic elastomer, and a method for extending the lifetime of DEA is also addressed.

Highly stretchable dielectric elastomer material based on acrylonitrile butadiene rubber

This study presents a highly stretchable dielectric elastomer material for transducers based on acrylonitrile butadiene rubber (NBR). The material has advantages in that its mechanical and electrical properties can be modified according to the requirements of applications by changing the content of additives such as carbon black (CB), multi-walled carbon nanotubes (MWCNT), and graphite (GP) in the NBR matrix. First, the changes of dielectric permittivity depending on the additives are discussed. Moreover, the electrical resistance is examined in detail by changing the compositions of the additives, and the applicability of the material to the electrodes of transducers is investigated. Finally, the optimal contents of additives for actuators or sensors are discussed.

Development of a smart handheld surgical tool with tactile feedback

This paper presents a handheld surgical tool adapting a tactile feedback system. The tool consists of a 3-degree-of-freedom (DOF) force sensor and three tactile displays. The sensor is easily embedded in the tool by adopting the capacitive transduction principle. The sensor measures the direction and magnitude of the 3-DOF force applied to the tool tip. The fingertip grasping the tool is stimulated by the tactile display to transmit the contact force information measured by the sensor. The tactile display is actuated by employing a soft actuator technology based on a dielectric elastomer actuator such as a type of electroactive polymer actuator. In this work, a prototype of the tool is designed and fabricated. Its performance is experimentally validated.

Biomimetic printable hexapod robot driven by soft actuator

This paper presents the preliminary design of a biomimetic printable hexapod robot driven by soft actuators. The robot mimics the insects design with six legs and shows the capability of versatile locomotion on flat terrains by using alternating tripod gait. The soft and multiple degree-of-freedom (multi-DOF) actuators based on dielectric elastomer provide required motions of the robot with a simple mechanism based on antagonistic configuration. The fabrication of the robot is effectively implemented by 3D printing method. In addition, a control system is built to provide various locomotion and walking speeds for the robot and its operation is demonstrated.

Highly sensitive proximity and tactile sensor based on composite with dielectric elastomer and carbon microcoils

This work presents a dual purpose sensor for collecting proximity and tactile information by using a composite with dielectric elastomer (DE) and Carbon Micro Coils (CMC). CMC is a coil-like carbon microstructure with the size of several hundred micrometers, and its electrical characteristics change with the distance between the object or via physical contact. Especially, the impedance change of the composite depending on the distance can be used as the principle for proximity sensing. We present a method to process the materials by using dielectric materials and additives. A prototype of the sensor is fabricated and its feasibility is experimentally validated.

A flying saucer lifted with Coandă effect

In this work, we present a flying saucer, a kind of unmanned aerial vehicle(UAV), lifted based on Coandă effect. Coandă effect is an interesting fluid dynamic phenomenon that the interaction between the flow and curved surfaces produce attraction, which results in the lifting of the object. The flying saucer adopting Coandă effect is easy to hover while keeping its posture stable, and vertical take-off and landing(VTOL) is possible. Its design procedures via optimization and manufacturing procedures are explained in details, and the preliminary tests in the indoor and outdoor are successfully demonstrated.

Preliminary design and fabrication of smart handheld surgical tool with tactile feedback

In this paper, we present a smart handheld surgical tool with tactile feedback to help microsurgery. This device consists of force sensors attached to the tool tip and tactile displays on the position of the fingerhold. The sensor is capacitive one and measures not only the magnitude of force, but also the direction of force. The sensor can measure 9N of lateral forces along x-y-z direction. The tactile display is based on dielectric elastomer actuators and made up of three rigid coupling tactile display modules. The tactile displays provide stimuli of 170μm displacement and frequency of 10Hz at the surgeons fingertips. We fabricate the device and its performances are experimentally validated.

Design and control of an unmanned aerial vehicle (UAV) based on the Coandă effect

In this paper, we present an unmanned aerial vehicle (UAV) called VTOL. we designed the overall shape of the UAV. we determined the optimal surface shape of the vehicle and the ratio of width to height of the saucer. Finally, we built the UAV and controlled its flight using anti-torque and flap links.