Jung-Sim Roh

Electromagnetic Shielding Effectiveness of Multifunctional Metal Composite Fabrics

The growth of the electronic industry and the widespread use of electronic equipment in communications, computations, automations, bio-medicine, space, and other purposes have led to many electromagnetic interference (EMI) problems as systems operate in close proximity. It is likely to become more severe in the future, unless proper EMI control methodology and techniques are used to meet the electromagnetic compatibility requirements. This article presents a comprehensive review of EMI shielding theory and materials. Furthermore, a method for fabricating a multifunctional metal composite fabric with electromagnetic (EM) shielding characteristics was successfully developed. The parameters influencing EM shielding properties of the metal composite fabrics were investigated. It was shown that the EM shielding effectiveness of the metal composite fabrics could be tailored by modifying the metal grid size and geometry.

Embroidered Wearable Multiresonant Folded Dipole Antenna for FM Reception

A wearable textile antenna with multiple resonance frequencies is proposed for the reception of FM signals using conductive embroidery of metal composite embroidery yarn (MCEY) on a polyester woven substrate. This embroidered FM antenna comprises five individual folded dipoles connected in parallel so that the bandwidth can be broadened via multiple resonances. The MCEY embroidered multiresonant folded dipole (MRFD) antenna is attached to a jacket, stretched from the left forearm, over the shoulder, and to the right forearm. The proposed antenna provides a wide operating band of 80.5 MHz to over 130 MHz at 5 dB return loss regardless of the arm movements, satisfying the FM broadcast band (87.5-108 MHz). The gain of this body-worn antenna is in the range of - 7.08 to - 15.79 dBd in the FM broadcast band regardless of the arm movements.

Wearable textile antennas

Owing to the rapid progress in fabrication technologies of conductive fibrous materials and the increasing demand for wireless communications in smart clothing systems, the potential application of wearable textile antennas in this field continues to increase. This article reviews a variety of wearable textile antennas in order to provide background information and application ideas for designing such antennas. The various materials used in the construction of wearable textile antennas, their fabrication methods, as well as the antenna types and their application fields are summarised. Owing to the high conductivity of metals, various metal composite yarns (MCYs) and fabrics have been used in the production of textile antennas. For inductively coupled near-field communication within smart clothing systems, woven or embroidered multiturn loop antennas are suggested. For far-field communication, a variety of broadband textile antennas were developed to counterbalance the detuning caused by the presence of a human body. Embroidered-folded dipole array antennas, metal-coated fabric patched bowtie and spiral antennas, a microstrip patch antenna array and a coplanar antenna made of metal-coated fabric patches and a ground plane, are the antennas that cover a broad spectrum and thus are capable of operating on the body.

Textile touch sensors for wearable and ubiquitous interfaces

The design of textile touch sensing interaction was explored with the new metal composite embroidery yarns (MCEYs) and a simple and easy fabrication technique aimed towards robust and reliable pressure sensitive position sensors for wearable tangible interfaces. In this paper, the resistive sensing method of a potentiometer as an accurate positional indicator was chosen to make simple prototypes of MCEY embroidered touch sensors. A simple structure of embroidered potentiometer to create textile switches as an input device in a smart textile system was tested. Both one- and two-point sensing method were successfully demonstrated. A complete success rate on switching was observed. These simple but ingenious embroidered touch sensors showed the possibility of a soft, lightweight, flexible, freely foldable touchpad as a ubiquitous solution. It was also shown that these minimal fabrication technologies may be highly valued in the smart textile field thanks to their simplified interconnections, customizability and tailorability on double curvature surfaces.

All-fabric intelligent temperature regulation system for smart clothing applications

The state-of-the-art in the field of smart interactive textiles is to develop a pure textile with smart electronics (all-fabric electronics). This article reports the production and testing of a temperature sensing and heating textile which consistently maintains a certain targeted temperature in order to provide optimal thermal comfort in everyday wear regardless of the internal microclimate and external climate conditions as well as the voltage level of the battery. The design and fabrication method of the robust, reliable, flexible, light, highly breathable, and simply constructed smart textile with dual functionality of temperature sensing and heating was explored with a metal composite embroidery yarn. The feasibility of the temperature regulating system based on the power on-off switching method referencing real-time temperature measured from the correlation between resistance and temperature of the heating metal composite embroidery yarn textile was shown. A uniform temperature distribution, a quick adjustment to a newly set temperature, and effective maintaining of a set temperature were identified. Many potential customized designs for smart garments will be possible in a wide range of fabric size, heating area, and different temperature requirement.

Thermal insulation properties of multifunctional metal composite fabrics

The thermal properties of metal composite fabrics (MCFs) are governed by the high thermal conductivity and low emissivity of the metal component. Metal type, metal yarn density, metal mesh openness and layering arrangement of the MCFs were varied to study how they affect the thermal insulation properties of the fabrics. Three types of thermal resistance (solid to solid, solid to convective air, and stagnant air to convective air) were measured. All MCFs tested showed higher solid to air thermal resistance compared to non-metal fabric. The solid to air thermal resistance of the MCFs showed either higher or lower values than those predicted from the metal content of the MCFs, depending on the openness aspect ratio of the metal mesh. The solid to air thermal resistance of stainless steel composite fabric was greatly enhanced by proper layering with non-metal fabrics. The results showed that the thermal insulation properties of MCFs can be improved by modifying the metal content, metal mesh openness and layering arrangement of MCFs with other fabrics.

All-fabric interconnection and one-stop production process for electronic textile sensors

This study developed and tested the development of an all-fabric interconnection and one-stop production process for electronic textiles that are combined with electronic technologies on textiles. Primarily, this is a one-stop production method for electronic textiles consisting of multilayer structured fabrics for implementation of electronic functions in which (1) precise circuit patterns are formed, (2) conductive materials or conductive circuits on each fabric layer are electrically connected, and (3) individual fabric layers are fixed to the base layer through embroidery, while fabric layers are layered one by one using a commercial computer numeric control embroidery machine. Since the multilayer fabric structured electronic textiles constructed have different layers of conductive materials connected electrically, quickly durably, and reliably through embroidery, (1) the electrically connected parts are not likely to be broken by external forces, (2) all parts to be connected to external devices are formed on one piece of fabric so that the work to connect the textiles to an external device is simple, and (3) workability and productivity are improved so that manufacturing costs can be reduced and the textiles can be mass produced. Therefore, this one-stop method using commercial machinery has great potential as a highly useful technology that can be implemented on an industrial scale.

Wearable electromagnetic energy-harvesting textiles based on human walking

The need for self-generating energy for outdoor environments is growing. To cope with emergencies in outdoor environments, sustainable, environment-independent energy-harvesting methods based on natural human movements are necessary. In this study, we developed a wearable energy-harvesting textile with a structure capable of generating the maximum energy from the swinging motion that occurs during walking. Two types of conductive yarn were manufactured and, when used as coils, are as durable as wire coils and have excellent flexibility and wearability, allowing easy integration into outdoor garments. Design variables related to the effect of energy production were investigated and the wearable energy-harvesting textile was evaluated by the average current generated. The conductive yarn coils can be connected in a serial circuit method and were evaluated to generate energy at a greater efficiency than wire coils. The average current increased as the number of turns of coil, the magnetic field, and the coil swing speed increased. The average currents along the distance between the magnet and the coil varied with magnet forces inversely proportional to distance.

User-centered Interface Design Approach for a Smart Heated Garment

This study aims to provide the possibility for future expansion of smart clothing through an analysis of interfaces based on user-centered design. This study designed interfaces for users that intuitively follow the needs of users of heated garments. Participants were asked to analyze the various elements of the system by wearing a smart heated garment in various situations in order to assess the objective performance, subjective usage satisfaction, acceptance, and differences of interfaces. The comprehensive analysis of the usability evaluation and user acceptance showed that interfaces based on usercentered design can give satisfaction to users. Furthermore, the textile switch which we developed provides more satisfaction and acceptance for use than do other interfaces because of its ease of use and accessability. This study provides additional meaningful information and improvements in the interfaces based on user-centered design of smart heated clothing.