| Real-time and accurate detection of body temperature is crucial to human health monitoring,disease diagnosis and treatment.The type of hand ring and stick devices,which packaging the traditiona l rigid sensor with a smaller volume,has been used to monit or body temperature.Although this device is capable of real-time and accurate monitoring,its combination of human body is not conducive for activity and comfort.In order to develop a wearable device to monitor body temperature,the temperature sensors based on fabric have been widely studied.The methods of combining the sensor with fabric by stitching and embedding have been used mostly.Although the sensor is integrated into the fabric,wearing comfort and appearance issues still exist.The use of fabric materials to achieve temperature-sensitive properties is the ideal way to prepare flexible fabric sensors.Weaving temperature sensitive metal fibers into fabric can not only achieve temperature sensing function,does not affect the wear and appearance,and can maintain the good performance of temperature sensing metal fibers.The use of knitting structure to fabricate the temperature sensing metal fibers into fabric has been studied.However,the signal stability as a sensor is relatively poor because of the poor stability of knitting fabric,and the sensor is vulnerable to environment.Based on the above problems,fabric-based temperature sensor was prepared by weaving method in this paper.Considering both the static temperature coefficient and the dynamic response time for the selection of metal fiber and the design of sensor.The static and dynamic temperature sensing performance were tested and evaluated respectively in the ideal conditions and the actual conditions.The research content were as followings:(1)The fabric temperature sensor is made by incorporating a continuous temperature-sensitive fiber into a woven fabric,which is flexible and light weight.A metal fiber is selected according to both temperature coefficient ratio and dynamic response time of the material.Platinum(Pt)fiber is the most suitable material for sensing element because of its high resistivity and temperature coefficient,and the smaller specific heat capacity.Higher resistivity and temperature coefficient are beneficial for higher sensitivity;sma ller specific heat capacity is beneficial for rapid response.In addition,fast response also requires a smaller sensor area.Therefore,considering both of the sensing area and the initial resistance,the sensing area was designed to be 1cm×1cm.Woven fabric temperature sensor with twill weaves was prepared in the semi-automatic loom by interweaving the Pt fiber as weft yarn.In order to avoid the impact of contact resistance,cotton yarn as another weft yarn was woven into adjacent Pt fibers.(2)The temperature sensing performance of fabric based sensor was explored in both oil bath and hotplate stage conditions.It was found that some performance of the sensor was easily affected by different conditions.The resistance of Pt fiber increases with the increase of temperature.The temperature-rising method in oil bath was used to measure the resistance at multi-point temperature to obtain the linearity,temperature coefficient,hysteresis and other properties.The response time was measured using the input method to realize a step change in temperature.The test results showed that the linearity of the temperature sensor with woven structure in silicone oil is 0.99975,and the temperature coefficient is 0.00362 /°C,and the static error is ±1.51% and the hysteresis is 4.20%.In order to study the sensing performance of sensor when in the condition c losed to practical application,a test system was built with a heating platform.The results showed that the linearity correlation coefficient is 0.99915,and the temperature coefficient is 0.00338 /°C,the static error is ±2.78% and the hysteresis is 3.26%.It can be drawn by comparing the test results under two conditions that linearity,temperature coefficient and hysteresis decreases,the static error increases because of the impact of environment.(3)Exploring the influence of test conditions on the dynamic response time,the results showed that heating conditions,the length of float,pressure and temperature range have a certain impact on the response time.Comparing the two heating conditions of oil bath and the heating platform;the float length of Pt fiber on both sides of fabric is different;applying different pressure on the fabric during the test;two types of yarns with different thermal conductivity are selected as the matrix materials;different temperatures are set by heating platform.The results showed that the response time measured in oil and heating platform are 1.032 s and 2.275 s,respectively.Appropriate increase of pressure in comfortable range is beneficial for response time.The temperature sensor prepared in this paper needs 200 Pa pressure.Reducing temperature range and increasing the contact length of fiber and heating platform in the same length of Pt fiber are beneficial for response time.Matrix material has almost no effect on response time(4)The sensor may be subjected to mechanical effects such as bending or twisting in actual applications.In order to improve the practicability of sensor,the Pt fiber was wrapped to be protected and enhance the mechanical properties of Pt fiber at same time.The temperature sensing Pt fiber was used as core yarn and the influence of wrapping material and twist on the mechanical properties of Pt fiber was explored.In addition,the temperature sensing performance of the sensor with wrapped Pt fiber was tested and evaluated.The test results showed that the breaking elongation of core Pt fiber is improved with 1000 twist/m because of buckles and the breaking load is improved significantly when covered by PA-DTY.As for the temperature sensing property of sensor,the temperature coefficient is 0.00314/°C,which was reduced by 7.10%.The response time was 3.317 s,which was increased by about 1s.Therefore,the temperature sensing properties of textile is realized by weaving method in the dissertation and the appearance and comfort of fabric is not been affected.Although the sensing performance of Pt fiber is affected by environment partly,it still mainta in its good sensing performance basically.The impact of test conditions on response time and the wrapping of Pt fiber laid the foundation for practicality. |
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