Jayoung Cho

Review and Reappraisal of Smart Clothing

Smart clothing is a “smart system” capable of sensing and communicating with environmental and the wearers conditions and stimuli. A comprehensive review is presented on the research and developments related to smart clothing including technology developments, human aspects in smart clothing, and the applications. Recent smart clothing technology can be summarized as a tendency toward textile-based technology for each component: interface, communication, data management, energy management, and integrated circuits. Human aspects in smart clothing, even though some areas were not fully covered, were dealt with in terms of usability, functionality, durability, safety, comfort, and fashion. General applications of smart clothing developed so far include bio-monitoring clothing, MP3 player-adopted clothing, and photonic clothing.

Exploring possibilities of ECG electrodes for bio-monitoring smartwear with cu sputtered fabrics

This article deals with a way of developing E-textiles using sputtering method and their possibilities as ECG electrodes for a bio-monitoring smartwear. As the market of smartwear is growing, researches toward E-textiles become more important. Among various ways of providing conductivity on textiles, we selected sputtering technology. Through the sputtering, we developed E-textiles deposited with thin Cu layer on the surface of the fabrics with thickness of about 2 micrometer. Then we measured the electrical resistances, examined their performances as ECG(electrocardiogram) electrodes and compared ECG signal measured with general AgCl electrodes. In result, ECG signals from Cu sputtered electrodes showed big potentials as textile-based electrodes by showing little difference in its signals compared with commonly used AgCl electrodes.

Physiological signal analyses of frictional sound by structural parameters of warp knitted fabrics

The purpose of this study is to offer acoustical database of warp knitted fabrics by investigating frictional sound properties and physiological responses according to structural parameters such as construction, lap form, and direction of mutual guide bar movement. Fabric sounds of seven warp knitted fabrics are recorded, and Zwicker’s psychoacoustic parameters — loudness(Z), sharpness(Z), roughness(Z), and fluctuation strength(Z) — are calculated. Also, physiological responses evoked by frictional sounds of warp knitted fabrics are measured such as electroencephalogram (EEG), the ratio of high frequency to low frequency (HF/LF), respiration rate (RESP), skin conductance level (SCL), and photoplethysmograph (PPG). In case of constructions, frictional sound of sharkskin having higher loudness(Z) and fluctuation strength(Z) increases RESP. By lap form, open lap has louder and larger fluctuating sound than closed lap, but there aren’t significant difference of physiological responses between open lap and closed lap. In direction of mutual guide bar movement, parallel direction evokes bigger changes of beta wave than counter direction because of its loud, rough, and fluctuating sound. Fluctuation strength(Z) and roughness(Z) are defined as important factors for predicting physiological responses in construction and mutual guide bar movement, respectively.

Physiological Responses Evoked by Fabric Sounds and Related Mechanical and Acoustical Properties

This study is performed to determine the characteristics of fabric sounds and the mechanical properties to predict their auditory comfort. In order to obtain quantitative information about emotional changes evoked by fabric sounds, physiological signals are acquired and analyzed when each fabric sound is presented to participants. Physiological parameters employed in this study are electroencephalogram and autonomic nervous system activities, including photoplethysmogram (PPG), skin conductance level (SCL), and the ratio of low frequency to high frequency (LF/HF) from the power spectrum of heart rate variability. As sound parameters, the pressure level of total sound (LPT), loudness(z), and sharpness(z) are calculated. Mechanical properties of the fabrics are measured with the KES-FB system. Bending hysteresis and weight. reflect negative sensations, influencing slow alpha, LF/HF, and SCL. Among sound parameters, LPT, loudness(z), and sharpness(z) influence negative sensations, causing the increment of SCL and LF/HF with the decrement of slow alpha and PPG.

Determining the Psychoacoustic Parameters That Affect Subjective Sensation of Fabric Sounds at Given Sound Pressures

In fabric sound research, loudness has been proven to be the primary factor determining auditory sensation while other factors have not received enough attention in relation to their significance. This study aimed to analyze the secondary sound factors that differentiate sensations of fabric sounds at given sound pressure levels (SPL) corresponding to loudness. Objective sound data were obtained with psychoacoustic measurements such as Zwickers parameters and auto correlation function parameters. These were compared with subjective ratings using seven pairs of descriptors: “hard vs. soft,” “quiet vs. loud,” “dull vs. sharp,” “obscure vs. clear,” “smooth vs. rough,” “low vs. high,” and “unpleasant vs. pleasant.” The fabric sounds having the same SPL varied in magnitude of perception for each sensation, thus revealing the effects of secondary sound factors. The parameters affecting subjective sensation are as follows: roughness ( z) and τ1, delay time of the first peak, decrease the sensations of “clarity,” “sharpness,” and “smoothness”; fluctuation strength (z) promotes “smoothness” for 50 dB sounds; and τe, related to reverberation, increases “pleasantness” for 50 dB sounds.

Physiological and subjective evaluation of the rustling sounds of polyester warp knitted fabrics

This study evaluates the rustling sounds of polyester warp knitted fabrics using a psychophysiological technique. We generate and record the rustling sounds of three structural types—reverse locknit, double denbigh, and sharkskin—of warp knitted fabrics, all made from 75D polyester filament yarn at the same density. To obtain quantitative information about rustling sounds, Zwicker’s psychoacoustic parameters—loudness(z), sharpness(z), roughness(z), and fluctuation strength(z)—are calculated from sound spectra obtained by FFT analysis. We acquire physiological signals—electroencephalogram, the ratio of low frequency to high frequency (LF/HF) from the power spectrum of heart rate variability, respiration rate (RESP), heart rate (HR)—from fourteen female participants when each sound is presented to them, and they rate seven sensations—softness, pleasantness, comfort, noisiness, annoyance, clearness, and highness—by free modulus magnitude estimation. Loudness(z), roughness(z), and fluctuation strength(z) are highest for the sharkskin and lowest for the reverse locknit. The rustling sound of double denbigh appears to be related to a positive sensation, with the highest softness, pleasantness, and comfort, and the lowest beta wave and LF/HF. On the other hand, the sharkskin sound appears to evoke negative sensations, with the highest annoyance and noisiness and most increasing beta wave, RESP, HR, and LF/HF. Therefore, we conclude that psychoacoustic parameters such as loudness(z), roughness(z), and fluctuation strength(z) affect psychological and physiological responses evoking negative sensations for warp knitted fabric sounds.

Design and evaluation of textile-based signal transmission lines and keypads for smart wear

The present paper was intended to prove the applications of surface-conductive fabrics as electronic textiles. First, we tested the electrical durability of a Cu/Ni electro-less plated fabric reinforced by PU(polyurethane) sealing. Using the fabric, we constructed textile-based signal transmission lines and textile-based keypads. For performance tests, we compared the output signals between the textile transmission lines and Cu cables and evaluated textile-based keypads by means of operation force and subjective operation feeling. PU sealing was effective to yield electrical durability for surface-conductive fabrics, thus the repeatedly-laundered fabric showed almost identical output signal with that of Cu, successfully operating an MP3 player. Subjective evaluation and operation force measurement identified that the rubber dome switch keypad was preferred due to a low operation force and less pressure on the skin when the keypad-mounted clothing is worn. The paper suggested specific applications and evaluation methods of electronic textiles as essential components for smart wear.

An exploration of electrolessly Cu/Ni plated polyester fabrics as e-textiles

Electrolessly Cu/Ni plated fabrics are favorable to be used as e-textiles owing to the excellent conductivity and the properties peculiar to fabrics. Nevertheless, durability is less ensured compared with Cu-based conductive lines. Therefore, we investigate the influence of abrasion and laundering on the electrical resistance of electrolessly Cu/Ni plated fabrics, and the effect of polyurethane sealing for the electrical durability.

Application of PU-sealing into Cu/Ni electroless plated polyester fabrics for e-textiles

Electroless metal plated fabrics are favorable to be used as e-textiles due to the excellent conductivity and peculiar properties of textiles such as flexibility. But, the electrical durability is not enough to be used as e-textiles. Therefore, we applied polyurethane(PU)-sealing (single-sealing vs. double-sealing) onto the electroless metal plated polyester fabrics (Ripstop vs. Mesh) to reinforce the electrical durability. We investigated the changes of electrical properties of the PU-sealed metal plated fabrics after laundering by a multi-meter, examined the surface changes using scanning electron microscope, and checked the metal existence using energy dispersive X-ray spectroscopy. And, we finally proved the possibility of the fabric strips as transmission lines by alternating conventional earphone lines. PU double-sealing showed higher performance on Ripstop polyester fabrics even after being laundered 10 times, which was almost the same as Cu-based typical conductive lines did.