【作者】 王海军；

【导师】 张婕；

【作者基本信息】 江南大学 ， 机械工程， 2023， 硕士

【摘要】 柔性应变传感器由于具有良好柔韧性和延展性,在健康监测、运动检测、电子皮肤和人机交互等多个领域具有广阔的应用前景。随着可穿戴设备的迅速发展,具有单一高性能的柔性应变传感器早已不能满足日常生产和生活的需要,同时具备高灵敏度和宽响应范围的柔性应变传感器的制备是目前的一大挑战。针对这一挑战,本文主要进行了基于改性碳纳米管导电复合材料制备研究和柔性裂纹应变传感器制备研究。具体研究内容和成果如下:针对导电复合材料的优化:通过硅烷偶联剂对多壁碳纳米管（MWCNTs）进行表面功能化,得到了表面接枝硅氧键的改性多壁碳纳米管（k-MWCNTs）。以聚二甲基硅氧烷（PDMS）为基体材料,碳纳米管为导电填料,制备了MWCNTs/PDMS导电复合材料（CPCs）和k-MWCNTs/PDMS导电复合材料（k CPCs）。k CPCs不仅在力学性能上比CPCs好,而且当碳纳米管质量分数为20%时,k CPCs的电阻比CPCs的电阻减小了1个数量级。在随后的传感性能测试中,k CPCs传感器在0-100%的应变下灵敏度为10.15,高于CPCs的灵敏度（4.23）两倍,在不同应变的拉伸循环测试中,与CPCs传感器展现的迟滞性相比,k CPCs传感器的响应曲线几乎没有迟滞。这充分说明碳纳米管改性后分散效果更好,与PDMS的结合也更加均匀、稳定。超高灵敏度柔性裂纹应变传感器:首先提出一种PDMS弹性层、k CPCs粘结层和脆性层结合的三层结构,脆性层材料（k CPCp）是将k-MWCNTs和PVP通过溶液共混法制备。基于该三层结构,通过丝网印刷工艺制备的柔性裂纹应变传感器,由弹性层提供可拉伸性,粘结层是传感器量程提升的关键层,同时提供粘结弹性层和脆性层的作用,脆性层形成裂纹并提供高灵敏度,然后通过调节三层结构中弹性层的力学性能、粘结层的电学性能来调节传感器的灵敏度和响应范围。当弹性层PDMS预聚体与固化剂的比例为15:1时,传感器的杨氏模量低至0.41 MPa,在200%应变下的拉伸和回复曲线几乎一样。当中间层k CPCs中碳纳米管质量分数为5%时,制备的传感器在20%的应变下ΔR/R₀的值为4×10⁴,灵敏度远高于同类研究。当中间层k CPCs中碳纳米管质量分数为20%时,制备的传感器在0-100%的宽应变范围内,ΔR/R₀的值为9.97×10²,且线性度也高达0.9895。高灵敏度和高线性度是高性能柔性应变传感器的两个关键指标。对高性能柔性裂纹应变传感器性能测试是以3/6/12/24/42 mm/min的拉伸速度在30%的应变下对其进行循环拉伸测试,传感器在五种速率下的循环均具有良好的一致性,同时传感器还具有0.01%的低极限应变检测和小于100 ms的迅速响应/恢复时间的优异特点。在0-50%的应变下,以10%的应变为阶梯进行传感器的稳定性测试,并在10%的应变下循环5000次,传感器的ΔR/R₀能稳定在40附近,表现出很好的稳定性和耐久性,且循环结束后电阻可以恢复到初始状态,没有迟滞。同时,该传感器能识别不同方向（内弯和外弯）的弯曲应变,并表现出相反的响应信号。针对高灵敏度/高响应度的传感特征,表征了高性能柔性裂纹应变传感器在可穿戴电子中应用的可行性。将传感器作为电子皮肤贴附于人体手指、四肢躯干、脸颊、嘴角和喉咙等部位,均可进行微小运动的特征识别及检测。在重物测试、防水和热传导等方面也表现良好。这说明该传感器能够作为可穿戴电子器件应用在人体运动检测和康复医疗领域,这种结合微纳结构及微纳材料设计的综合调控方法为制备高性能的柔性应变传感器提供了新的技术路线。更多还原

【Abstract】 Flexible strain sensors have broad application prospects in various fields such as health monitoring,motion detection,electronic skin and human-computer interaction due to their good flexibility and ductility.With the rapid development of wearable devices,the high-performance flexible strain sensor has long been demainded to meet the needs of daily production and life.The preparation of flexible strain sensors with both high sensitivity and wide response range is a major challenge which is addressed as following in this studys:For conductive composites,multi-walled carbon nanotubes（MWCNTs）were functionalized by silane coupling agents to obtain modified multi-walled carbon nanotubes（k-MWCNTs）with silicon-oxygen bonds grafted on the surface.MWCNTs/PDMS conductive composites（CPCs）and k-MWCNTs/PDMS conductive composites（k CPCs）were prepared using polydimethylsiloxane（PDMS）as the matrix materials and carbon nanotubes as the conductive fillers.k CPCs were not only better than CPCs in terms of mechanical properties,but also 1 order of magnitude lower the resistance when the mass fraction of carbon nanotubes was 20%.In the subsequent sensing performance test,the sensitivity of the k CPCs sensor was10.15 at 0-100%strain,which was doubled that of CPCs（4.23）.Under tensile cycling with different strains,the response curve of the k CPCs sensor showed almost no hysteresis compared to the hysteresis exhibited by the CPCs sensor.It indicates that the carbon nanotubes are uniformly and stably dispersed in PDMS after modification.In the flexible strain sensors with induced surface crack development,a three-layer structure combining PDMS elastic layer,k CPCs bonded layer and brittle layer is proposed.The brittle layer material（k CPCp）is prepared by solution blending method of k-MWCNTs and PVP.Based on this three-layer structure,the flexible crack strain sensors were printed by screen printing.In this device architecture,the elastic layer provides stretchability,the binder layer determins the measurement range in addition to bond the elastic and brittle layers,the brittle layer forms cracks and provides high sensitivity,respectively.The sensitivity and response range of the sensor are further tuned by adjusting the mechanical properties of the elastic layer and the electrical properties of the binder layer.When the ratio of PDMS prepolymer to curing agent in the elastic layer is 15:1,the Young’s modulus of the sensor is as low as 0.41 MPa,and the tensile/recovery response at 200%strain are very repeatable.When the mass fraction of carbon nanotubes in the intermediate layer k CPCs was 5%,theΔR/R₀ at 20%strain has reached4×10⁴,which was much more sensitive than similar studies reported in the literatures.When the mass fraction of carbon nanotubes in the intermediate layer k CPCs was 20%,theΔR/R₀ was9.97×10² at the 0-100%strain range for the prepared sensors with the linearity as high as 0.9895,which is the typic high-performance flexible strain sensor prepared in this paper.The sensing performance of the flexible crack strain sensor was tested by cyclic stretching at 30%strain at 3/6/12/24/42 mm/min moving rate.The sensor showed good consistency in cycling for all five rates.The sensor was also capateble of detecting the low strain of 0.01%and a response/recovery time of less than 100 ms.The sensor was tested in steps of 10%strain at 0-50%strain range.The sensor exhibits good stability with 5000 cycles at 10%strain,theΔR/R₀ of the sensor was stabilized around 40,showing good durability.The initial resistance could be restored after the cycle tests.In addition,the sensor can recognize bending strains in directions（inward and outward bending）and exhibited opposite response signals.Finally,the wearability and other applications of high-performance flexible crack strain sensors were also demonstrated.Motion detection was illustrated by attaching the sensor skin to the fingers,limb torsos,cheeks,corners of the mouth and throat of the human body.It also performs well in terms of heavy weight testing,water resistance and thermal conductivity.This indicates that the sensor has the potential to be applied to human motion detection and wearable electronics applications.This cohesive modulation of the structure and materials properties provides a new strategy in preparation of high-performance flexible strain sensors.更多还原