基于高弹性耐疲劳铜纳米线/聚合物气凝胶组装体的柔性压阻传感器研究

At present, there are still a series of problems to be settled in piezo-resistance transducer: such as insufficient adaptability, low reliability and weak large-scale expandability. In this proposal, based on the electron transmission and mechanical support design, a new research strategy via controllable macroscopic three-dimensional (3D) assembly of nanostructure is proposed to construct highly sensitive, resilient and endurable flexible piezo-resistive system and achieve fundamental sensing material innovation. For the key restrictive factor on mechanic-electric signal transition of force sensing element, and its resilience deterioration caused by local microstructural damage under high loading stress, the main idea mainly focus on microcosmic structural modulation. Motivated by our recent explorations, five-twinned copper nanowire (Cu NW) is selected in the project as building block of piezo-resistive materials, and we aim to develop accurate assembly methods by utilizing elastomer aggrandizement and directional freezing technique to regulate the arrangement of nanowires in macroscopic 3D space. New types of high resilient and fatigue-resistant ordered hierarchical porous aerogel monoliths could be built with a mix of macroscopic percolation and microcosmic tunneling traits to meet the requirements for practical applications. With the aids of complete characterization and performance testing, the microscopic mechanism of the conductivity and piezo-resistivity of Cu NW networks embedded in polymer matrix will be revealed, and the structure-properties relationship can also be established. By further inspecting the influence of the contact electrodes excogitation and integrated methodology on the systematic flexibility and stability of the sensing element, the synergetic effect exerted by integration of each functional component will be clarified. Ultimately, these works will help gain the overall performance improvements of sensing system and tackle the key scientific problems related to the multiple-scale optimization in design. We believe that our methodologies in this project will provide theoretical and practical instructions for the design of new-fashioned micro-and nanosensors.

为解决目前压阻式传感器适应性、可靠性不足和规模化扩展困难等焦点问题，本项目拟以电子传输和力学支撑设计为基础，以微纳结构的三维有序组装为手段，构建兼具高灵敏性、高回弹性和高稳定性的柔性压阻力敏系统，实现传感材料源头创新。研究将基于压阻材料力电信号转换的关键制约因素和高应力载荷下微结构损伤导致的回弹性衰减等机制分析，以五重孪晶铜纳米线为模块基元，结合聚合物复合强化与定向冷冻技术，开发弹性体中纳米线空间搭接状态的精准调控策略，获得具有宏观渗流和微观隧穿导电特征的高弹性耐疲劳气凝胶力敏材料。通过系统表征和性能测试，研究铜纳米线网络导电特性与力敏效应的微观机理，揭示构效关系规律。进而考察读出电极设计和集成工艺对传感元件柔顺性和稳定性的影响，明确由各功能组分耦合诱发的协同作用机制。最终，达成力敏系统综合性能的增强，解决其多尺度设计优化这一关键科学问题，为新型微纳传感器件的研制提供理论依据和实践借鉴。

三维自支撑气凝胶组装体是一类极具广泛应用潜力的柔性功能材料。该类材料稳定制备工艺的开发，性能调控以及对其结构基元微观物理特性跨尺度传递机制的理解，一直以来都是学界关注的热点。对此，本项目从基础单元结构的理性设计出发，通过发展孪晶强化、原位聚合、定向成型等关键合成工艺，成功获得了一系列力、电、热性能可调，具有三维联锁骨架微结构的半导体铜@聚吡咯核壳纳米线气凝胶材料。在此基础上，采用原位透射电镜、原子力扫描探针技术，首次实现了单根纳米线结构基元包括机械形变、电输运、热传递以及光波导等在内的基本物理特性参数测量和成像，为宏观器件性能的微观机理阐释提供了重要的实验依据。代表性结论主要有：.（1）发现了利用纳米尺度共格孪晶界面强化提高金属纳米材料强韧性的新途径。经微波合成围有{111}和{100}低指数晶面Wulff类多面体形成的<100nm小尺寸铜纳米线，其特有的纳米尺度共格孪晶结构不仅可有效降低晶体中电迁移损伤，其与位错的独特相互作用还可显著提高应变强度（>6.5GPa）与塑性延展能力（>6%）。.（2）发展了酸减缓冲调控的化学氧化原位聚合策略，获得了孪晶内核保存完整的高质量铜@聚吡咯核壳纳米线。通过侧向冰模板组装，进一步制取了具有多级互锁联拱层状结构的宏观气凝胶组装体。该材料在应变60%时最大应力可达37kPa，循环压缩300次无衰减，压阻灵敏度>0.47kPa-1，响应时间<2ms，检测限<6Pa。.（3）发现并探索了铜@聚吡咯核壳纳米线气凝胶卓越光热转换特性的内在增强机制。五孪晶铜纳米线内核具有很强的局域SPR效应，热电子激发效果显著，而法布里-珀罗共振行为导致的朗道阻尼使热电子更多转换为声子。同时，聚吡咯外壳一方面可以显著拓宽光谱吸收范围，另一方面其本征低导热特性产生了良好的隔热效果，协同气凝胶网络促进了集热效应，在4000W/m2光强辐照下，20s内可升温至220℃以上。