【作者】 陈大竞；

【导师】 陈裕泉；

【作者基本信息】 浙江大学 ， 微纳传感器， 2011， 博士

【摘要】 微纳尺度传感器在器件体积、功耗、灵敏度、重复性、成本、生产控制等方面较传统传感器都有较大的优势,纳米技术和MEMS传感器两种技术的结合使传感器进一步朝集成化、智能化发展,大幅提升了传感灵敏度、选择性和可靠性。目前基于微纳结构的传感器已逐渐成为物理、化学、生物领域众多传感器采用的一种重要结构形式。微纳纤维型传感器作为微纳传感器的一重要组成部分,由于其便于制备控制,便于定量分析,适于和微纳结构结合而获得了广泛的关注。本文对聚合物纳米纤维的制备、合成、压电特性、气敏特性和气敏机理等有关问题进行了较为系统的研究。主要研究内容如下：在现有静电纺丝基础上,使用近场电纺技术制备了外形、结构可控的聚合物单根纳米纤维／纤维阵列,为深入分析纤维压电、气敏机理提供了可能,通过控制电纺过程的工艺参数对纤维形态进行控制,探讨了不同材料、不同条件参数对近场电纺过程和结果的影响。制备了聚偏氟乙烯纤维,进行了可纺性研究和配比优化。在电纺过程中直接利用了高电场和大拉伸比,有效地提高了纤维中β相比例,从而使制备的纤维具有比传统压电薄膜更高的压电系数和单位电荷输出效应。设计了专用电荷放大器,可对微小电荷量进行引出。经测试该压电纤维具有良好的机-电转化特性,转化效率高于传统聚偏氟乙烯膜,在压力传感、人工触觉,微纳发电等领域都具有良好的应用前景。研究单根导电聚合物纤维的电特性,测试了纤维与不同电极材料的接触特性,对肖特基接触的产生条件进行了研究。应用MEMS技术研制了单纤维场效应特性测试平台,实验数据说明聚苯胺纤维具备场效应,在柔性电路,有机半导体等方面有着良好的应用。实验说明质子酸掺杂的聚苯胺纤维具有优越的场效应性能和氨气气敏特性,可有效利用场效应结构控制纤维内部载流子活动,提升其气敏性能,可有效检测低至1ppm浓度的氨气。以气敏选择性高、灵敏度高为目标,使用纳米钯颗粒材料对导电聚合物纤维进行了掺杂,制备获得功能材料颗粒-导电聚合物的混合纤维,对氢气具有高灵敏响应,为制备阵列型多目标气体传感器提供了良好平台。纳米纤维设计发挥了纳米材料比表面积大,灵敏度高的优势,同时结构稳定,对1%浓度氢气响应灵敏度为1.07。提出了柔性串珠纳米钯微粒结构单根纤维模型。柔性导电纤维材料连结钯粒子,避免了钯功能粒子因吸氢作用体积膨胀造成的传感器重复测试失效等问题,又突破了目前离散钯粒子氢气测量范围有限的局限,有效氢气浓度测量范围从传统的4%左右扩展超过10%。通过控制电纺参数对制备得纤维直径进行了有效控制,通过实验验证了纤维直径对气敏响应灵敏度、响应时间、脱附时间的影响,提出了功能材料颗粒-导电聚合物混合纤维的等效电路模型,结合气体扩散公式验证了气敏实验数据,为传感器改性提供了理论依据。更多还原

【Abstract】 The nano-fabrication technology and micro electronics and mechanism system offer the promise of improved sensors with small size, low-power consumption, high sensitivity, fast response time and reliable repeatability. There are increasing demands for nano/micro sensors in physical, chemical and bio-sensing areas. Nano/micro fiber sensor, as part of nano/micro sensors, draws wide attention due to its adaptability to micro electronic system. This dissertation presents the synthetic procedure, piezoelectric sensing and gas sensing characteristics.Based on current electrospinning methods, near field electrospinning is used to synthesize controllable single polymer fiber and aligned fiber array. This synthetic procedure has unique properties over its bulk counterparts, which provides the possibility to analysis piezoelectrical and gas sensing mechanism deeply. Different materials, fabrication parameters and environment conditions are compared to optimize the fiber characteristics.poly(vinylidene fluoride) fiber is synthesized by near field electrospinning. Compared with conventional electrospinning, near field electrospinning provides higher electrical field which brings better fiber polling effect. PVDF fiber showed higher piezoelectricity efficiency than conventional PVDF film. These fibers will be attractive for many applications, including pressure sensor, tactile sensor and energy harvester.Singl e polyaniline nanof iber was investigated to understand electrical performance and sensing mechanisms. The fibers showed Schottky contact and ohmic contact based on different electrode materials. We studied the morphology, field effect characteristics and gas sensitivity of conductive nanofibers. Conductive nanofiber could be promising for flexible circuits and organic semiconductor applications. Applied higher gate voltage will contribute to the increase in gas sensitivity. The FET characteristics of sensor exposed to different gas concentrations indicate that adsorption of NH3 molecules reduce the carrier mobility in polyaniline nanofiber.The need for selective gas sensors with high sensitivity, and fast response is increasing for various applications. Metals and metal salts exhibit selective changes in the working function on exposure to specific gases. In this dissertation, polyaniline nanofibers doped with palladium nanoparticles have been deposited in control led 2-D patterns across two gold electrodes by near field electrospinning without the conventional lithography process. We successfully fabricated single polyaniline hybrid nanofiber with ultra low power consumption. Test results indicated the nanofiber gas sensors have the advantages of selectivity, sensitivity and reversibility. Polymer and palladium hybrid could form a flexible structure to minimize the effect of lattice expanding for stable sensing structure in hydrogen sensing.The diameter of fiber can be controlled by many factors, including bias voltage, needle-to-electrode distance, as well as the solution concentrations. Fibers with different diameters are tested to verify the response time. Metal-polymer hybrid equivalent model and gas diffusion mechanism are developed in the dissertation. This theory will contributes to future improvements of gas sensors.更多还原