Investigation Of Conductivity And Response Properties Of Intelligent Sensing Fabrics

With the progress of the science and technology,particularly the rapid development of information and micro-electronics technology,smart textiles which contain micro-electronics,information,computer technology are becoming a hot research topic within the forefront of textile technology.It usually consists of three parts,including sensors,drive units and control unit, which guarantee a corresponding signal processing and feedback in accordance with the requirements of different real-time stimuli acquisition. At present,both drive unit and control unit are usually driven by sophisticated hardware control technologies such as the micro-electronics and computer chips.The sensor,as a core component of smart textiles,is a key element which determines not only the intelligent performance but also the comfort performance of textiles.Smart textiles,widely used in electronic, medical and military fields as well as biological textiles known as "second skin",will bring out prosperous market in the 21^st century.Based on domestic and international theoretical studies about conductive smart textiles,this research work is to improve the current chemical vapor deposition processing in fabricating the electrical conducting fabrics by using self-designed device to produce electrical conducting PPy fabrics,sensitive to external stretch,under low temperature and low pressure conditions.This has greatly increased the fabricating efficiency.By using orthogonal experiment,static and dynamic surface electrical resistances are measured respectively.The effects of antioxidants concentration,dopant concentration,polymerization temperature,polymerization time on the electrical conductivity,sensitivity to the stretch stimulus as well as signal responding stability of conductive fabrics are explored and discussed in details.The proper processing parameters have been worked out for producing the fabrics which have reliable sensing and responding ability.Three series of elastic weft knitted fabrics and polyester/spandex woven fabrics have been made to be the substrates for flexible sensors with conventional fibers and special-shaped cross section fibers respectively.They are polymerized using chemical vapor deposition under low-temperature and low-pressure conditions in order to fabricate the electrically conducting textiles with good electrical response to the external mechanical stimuli.By analyzing the electrical conductivity,responding sensitivity and stability of polymerized fabrics,the relationship between fiber types,fabric structures and their performance as flexible sensors are investigated.This research work has provided a reliable theoretical basis for reasonably selecting the proper substrates used for good intelligent flexible sensors.An alarming system with on-line display,consisting of stretching device, measuring circuit,single-chip,computer with relevant software,has been designed and constructed for testing the performance of sensing fabrics after various stretching theories are well studied and analyzed.Tests show that the data acquisition system can accurately capture the change in data of different fabric surface resistances when the fabrics are subjected to various stretches. It has well simulated the sensing performance of fabrics when they are exerted dynamic stretching.A unique real time alarming system is thus established.The high-performance single-chip ATmega169V has been used to replace the traditional data acquisition system including data collecting and data processing,microprocessor and output interface.The system not only can meet the requirements for data processing but also can simplify the structure.By setting the internal procedures of the chip and peripheral circuits while MAX232 chip is connected to a computer serial port,the collected data can be displayed directly on the computer.When the value of surface resistance of conductive fabric,after the fabric is stretched,is lower than the pre-set threshold,the system makes beeping sound.By adjusting standard values of electrical resistance in the test circuit,the system sensitivity of response to the stretch can improve effectively.The effectiveness and reliability of the system has shown the preliminary model of flexible sensor which can act really "smart" behavior.The theory,method and the experimental data in this research work have provided important and valuable theoretical and practical bases for further development of smart textiles.