Gil-Yong Lee

Hand-arm vibration exposure is a recognized occupational hazard that can cause discomfort and long-term disorders. While anti-vibration gloves are commonly used to reduce these effects, their effectiveness is often limited by the stiffness of the materials and structural constraints. This study focuses on the development and evaluation of polydimethylsiloxane (PDMS)- based anti-vibration layers with varying internal structures for use in anti-vibration gloves. We prepared three types of PDMS layers: solid PDMS without pores (SPDMS), porous PDMS foam created through a sugar-leaching process (FPDMS), and a hybrid PDMS structure that combines solid and porous layers (HPDMS), all shaped like palms. These PDMS layers were integrated into glove specimens, and their vibration transmissibility was assessed using a measurement system compliant with ISO 10819:2013. Vibration transmissibility was recorded across one-third octave bands from 25 to 1,250 Hz, and frequency-weighted transmissibility values were calculated for both the M- and H-spectra. The results indicate that PDMSbased anti-vibration layers with controlled porosity can be effectively fabricated and incorporated into glove structures, and that variations in internal porosity significantly impact the measured vibration transmissibility characteristics.

Electromyography (EMG) signals are widely used in human-computer interaction (HCI) due to their high signal-to-noise ratio and ability to provide early information about muscle contractions. In this study, we present a mobile vehicle remotely controlled by EMG signals captured from hand-arm gestures. Specifically, we investigated gripping and wrist gestures. A single EMG sensor placed on the right forearm captured signals during gripping gestures with varying grip forces. Two EMG sensors placed on the left forearm recorded signals during wrist gestures with varying wrist folding angles. The EMG signals from the gripping gestures were evaluated based on grip force. The root mean square (RMS) value of these signals was used to control the driving speed and direction of the mobile vehicle. Similarly, the EMG signals from wrist gestures at different folding angles were characterized and used for differential speed control of the vehicle's driving wheels. A series of reliable demonstrations showcased the remote control of the mobile vehicle prototype using grip force and wrist gestures. Our approach is simple, effective, and reliable, achieving omnidirectional mobile vehicle control with both gesture-to-motion and sensor-to-motion ratios of 1.67, thereby contributing to appropriate technology for mobile and intelligent vehicles and related engineering and scientific applications, with a cost-effective design and simple configuration and operation.

We present an extrusion-based dispensing system designed for the planar patterning of tungsten ink through direct ink writing. This system achieves uniform ink deposition by precisely controlling the dispensing pressure and the motion of the substrate along predefined writing paths. To assess the impact of pressure on pattern geometry, we fabricated line patterns under various pressure conditions and analyzed their widths and thicknesses. To gain further control over pattern width, we employed an adjacent line overlapping strategy, where several lines, each approximately 200 μm wide, were written with partial overlap. We quantitatively verified the relationship between the number of adjacent lines and the resulting pattern width. This method was also adapted to create planar patterns with complex geometries, including variable widths, curved paths, and discontinuous features. The resulting patterns demonstrated uniform quality and precision. These findings confirm that our proposed system provides a versatile solution for fabricating planar conductive patterns with intricate geometries, suitable for applications in printed electronics and interconnects.

We present a new type of torsional soft morphing actuator designed and fabricated by twisted shape memory alloy (SMA) wires embedded in polydimethylsiloxane matrix. The design and fabrication process of the proposed soft morphing actuator are presented with investigations of its working mechanism. Actuation performance was evaluated with respect to the temporal response, the maximum torsional deformation under an applied electric current, and various design parameters including the twist direction, wire diameter, helical pitch of the SMA wire, and the actuator’s thickness and length. We demonstrate potential applications of the proposed soft morphing actuator as a soft morphing wing and airfoil. The proposed actuator will aid in the development of soft actuators, soft robotics, and other relevant scientific and engineering applications.

The objective of this study was to present a rotary manipulating system driven by a rotary actuator based on twisted shape memory alloy (SMA) wires. The rotary actuator was composed of two oppositely twisted SMA wires connecting a rotor and a stator through a shaft. Two oppositely twisted SMA wires could generate bidirectional rotary motions upon actuation of each twisted SMA wire corresponding to the direction against the twist direction of each SMA wire. A manipulator was designed and fabricated by integrating manipulating arms, the rotary actuator, and a Hall effect magnetic rotary encoder which could measure the angular position of the rotary motion. We modeled and characterized the manipulator upon application of a ramp current input to each twisted SMA wire. A proportional-integral-derivative (PID) controller was designed and implemented to control the proposed rotary manipulator. Reference angular position tracking performances of the manipulator were evaluated with a series of experiments.