In this paper, we propose a physiological stress measurement method that uses a fiber Bragg grating (FBG) sensor. There are several points on the surface of the human body at which the pulse wave can be measured, and when an FBG sensor can be positioned at any of these points, to measure the pulse wave signal. When a person is under stress, their pulse rate increases and the peak interval in the measured pulse wave signal becomes shorter. This peak interval change can be measured using the FBG sensor and analyzed using a Poincaré plot; the stress load can then be detected based on the shift in the plot position. The points on the Poincaré plot shift toward the lower left direction because of the stress loading. Depending on the amount of applied stress, the length by which the plot shifts changes. When the proposed measurement method is used, it is possible to continuously monitor a subject for stress by simply installing the optical fiber at a pulsation point. When optical fibers are woven into textile products, it becomes possible to detect stress load by wearing a modified garment. Therefore, this measurement method can be applied as a wearable stress sensor in smart textiles.

The recent development of functional materials, including smart textiles, has enabled the development of wearable biosignal measurement devices that are easy to handle and can be used on a daily basis, even by non-medical users. We focused on sleep disorders as a preliminary application for wearable devices, which are reported to be associated with or exacerbate other diseases, and must therefore be detected early and treated appropriately based on the usual sleep status of the patient. Periodic limb movement disorder (PLMD), which induces nocturnal awakening due to PLM while sleeping, is a sleep disorder that is thought to affect a considerable number of individuals. Since polysomnography (PSG), which needs time consuming hospitalization and forces a financial burden on the patient, is the only practical method for PLMD screening, some PLMD patients are supported to be remain undiagnosed and untreated.

In order to resolve this situation, we aim to develop a PLM home monitoring system that consists of fabric adapters and fabric electrodes that can detect PLMs based on surface electromyogram (SEMG) measurement, without disturbing the usual sleep of subject. We developed a prototype SEMG measurement system that combined ready-made stretchy socks and fabric electrodes that can be easily handled by the patients without any medical knowledge. This prototype can prevent measurement faults due to the slippage of measurement electrodes as the measurement electrodes are fixed by the pressure of the fabric adapter. We first evaluated the functional ability in voluntary movements by comparing the SEMG obtained with the prototype to that obtained using conventional electrodes. We then performed SEMG measurement while PLMs and confirmed that the prototype has the potential to discriminate PLMs from voluntary movements. The proposed sockstype SEMG measurement device is expected to be able to precisely quantify PLMs, even when handled by non-medical users in their home.

This paper describes a pulse wave sensing textile to measure pulse wave continuously without stress. Due to aging population, the attention is focused on measurement of vital signs during daily life. Blood pressure (BP) is widely used as an index representing the state of the circulatory system. BP can be estimated from electrocardiogram (ECG) and photoplethysmogram (PPG). PPG can be obtained by a combination of a light emitting diode (LED) and a phototransistor (PT). The textile measured PPG has not been realized although there are fabric electrodes for measuring ECG. Therefore we developed the pulse wave sensing textile for using underwear aiming to continuously BP estimation. By using conductive fibers woven into the textile as wiring, the pulse wave sensing textile is realized. In order to improve the stability of pulse wave measurement, LEDs and PTs were arranged in array on the textile. We designed the textile circuit under the consideration that circuit lines on the textile must be straight. We showed that arranging LEDs and PTs in an array improve the stability of pulse detection and evaluated that the proposed sensing textile can be measured pulse wave on the waist even if a person attached the proposed sensing textile is moving. These results suggest that the proposed sensing textile could be built into underwear and used as a part of BP estimation system. Unconscious continuous BP monitoring underwear could be realized by combining the proposed textile with fabric electrodes.

It is desirable that a medical system should begin therapy before diseases reach severe stages. To realize such a system, vital signs should be monitored continuously. As an approach, we have worked on smart textiles for monitoring vital signs. In particular, a fiber Bragg grating (FBG) sensor is an excellent device because of its high performance, low cost, and fiber- or yarn-like form that is considered to be suitable for textile processes. In this study, we examined the measurement signal intensity for calculated blood pressure using a covered FBG sensor embedded into knitted fabric. An FBG sensor covered with silk thread was developed and embedded into tubular knitted fabric using inlay knitting technology. Next, a pulse wave signal was measured using this covered FBG sensor embedded into knitted fabric. Results showed that clothing pressure changed according to the number of wales of the knitted fabric and clothing pressure strongly influenced the detection of the pulse wave signal. Even though there is scope for improving this sensor as a wearable system, we found that it is possible to use the sensor in smart textiles for monitoring vital signs.

Natural fibers are often used as a continuous twisted yarn, which are suitable for reinforcement of fibrous composites. In the twisted yarn, we often encounter phenomenon called ʻmigrationʼ, which means,single yarns (spun yarns) shift from outer layer to inner and vice versa. In this study, we first observed migration structure of ramie twisted yarns through an X-ray CT scanner. Results showed that migration occurred irregularly in the yarn, from which we found three kinds of single yarnsʼarray patterns, i.e. Regular array (RA), Inside superior array (IS), Outside superior array (OS). RA means that a cross-section is composed of seven and twelve single yarns in the inside and outside layers, respectively. IS means that the number of single yarns in the inside is more than RA, and OS means that the number of the outside is more. These patterns were found to have a correlation with the number of single yarns involving migration. This phenomenon was also simulated by Markov chain model. Finally, the effect of migration on tensile properties was clarified such that, when the number of IS occupies more in a specimen, this yarn structure leads to higher tensile strength.

Okinawa Island is part of the Ryukyu Islands located in southern Japan. Basho-fu is a unique and traditional Okinawan textile made from the banana plant Itobasho. The traditional production process of Bashofu has not been well studied scientifically. In this study, materials from the traditional degumming process (Udaki) of Basho-fu were characterized by morphological observation and other analytical instruments (FT-IR and XRD). The fiber materials degummed by the traditional and the modern laboratory methods were compared. The vascular bundles of the main component of Basho-fu fibers were conserved in the materials processed by the two degumming methods. However the FT-IR study indicated that the traditional method was milder than the laboratory process. The results scientifically confirms that the delicate traditional degumming step is a crucial process in the production of the fine Basho-fu textiles.

Naturally cocooning of Bombyx mori silkworms was analyzed applying the allometric scaling method to the statistics data on the non-genetically modified Bombyx mori silkworms of 188 breeds including G₀,F₁,F₁× G₀,andF₂, and discussions were made from the viewpoint of the body size effect on the tensile properties,fineness of raw silk threads. The strategically controlled line-breeding effectively cured the unfavorable spinning habits of silkworms and could bring about the production of cocoons fabricated by a longer filament with a higher reelability. The positive body size effect on the fineness of raw silk threads was confirmed. However, the tensile strengths of raw silk threads concentrated around 4 gf/d and were almost independent of the body size of silkworms. The raw silk threads of cocoons obtained in September and/or October showed slightly lower tensile elongation at break compared with June. However, no significance was recognized under the condition of P<0.05. It was thought that the excess intake of metallic compounds by silkworms through digesting mulberry leaves is not likely to affect the tensile properties of cocoon threads.