基于磁致热温敏型静电纺纤维膜致动器的构筑及其致动机理研究

Thermoresponsive actuator has inspired a lot of scientists' interesting in recent years due to the ability of performing mechanical motions when exposed to an external temperature changing. It offers a great potential for a number of applications in various fields. However the challenges are still there. Firstly, most of these kinds of actuators are in the form of polymer films leading to low water diffusion rate which contributes to low sensitivity. Secondly, the performance of mechanical motions are mostly achieved by heating up the entire surround environmental system resulting in low heat transfer efficiency and uneven heat transfer. Therefore, it would be desirable to design such a kind of thermoresponsive actuator with high sensitivity but unnecessarily heating up the entire surround environmental system. In our previous studies, it has been demonstrated that electrospun fibrous mat can provide thermoresponsive actuator with high sensitivity. Combining the magnetothermal property of Fe3O4 particles, we assume that it is possible to create a thermoresponsive actuator with the ability of high sensitivity and penetrating remotely controlled property by incorporating local heating spots into electrospun fibers. First of all, a fibrous mat with Fe3O4 particles uniformly distributed in fibers will be fabricated by electrospinning technology; then the effect of magnetic field frequency, magnetic strength and other parameters on the fibrous mat will be studied; finally, a bilayered thermoresponsive actuator will be created by combing the other layer of non-stimuli-responsive polymer, followed by investigating and characterizing its actuation behavior. The research of this project may give help to the design of new thermoresponsive actuators and the novel polymeric actuators.

作为当前的研究热点，温敏型智能致动器可以利用周围环境的热能转换为机械能，在很多领域内表现出诱人的应用前景。然而目前面临的挑战，一是该种智能致动器主要以聚合物薄膜的形式存在，响应灵敏度低，二是被动地依靠外界热源对系统整体进行加热，传热效率低且不均匀，不利于致动行为的精确表达，应用范围有限。我们前期研究发现，超细纤维膜可以赋予温敏型智能致动器高灵敏性，结合Fe3O4的磁致热性能，因此提出假说：在超细纤维膜的纤维内，内置热源，通过磁场进行原位加热，实现对致动器的快速、远程、穿透式操控。本项目拟首先通过静电纺丝技术制备Fe3O4颗粒均匀分布的温敏型静电纺纤维膜，然后研究磁场频率和强度等因素对纤维膜的影响，最终结合另一层非响应型材料制备具有双层结构的温敏型致动器，探究影响致动的因素，阐明致动行为的规律，揭示致动的机理，为温敏型智能致动器的深入研究奠定基础，为新型智能致动器的设计提供新思路。

温敏型智能致动器具有对外界环境温度变化刺激做出机械行为响应的能力，在柔性机器人和生物医用领域展现出一定的应用潜质。其本质是将热能的变化转变成机械能的变化。因此，能量的转化、传递方式和效率将直接影响其综合表现。当前研究主要以聚合物薄膜为研究对象，多聚焦于丰富其刺激的多样性，而对于能量转化、传递研究较少。本项目借助静电纺丝技术，内嵌磁热转化颗粒制备纳米纤维薄膜，从能量的传递和转化角度对温敏型智能致动器进行研究。研究内容主要包括： (1) 探究通过改变能量转换方式赋予致动器隔空穿透式操控的可行性； (2) 通过改变能量传递方式，阐明其快速响应的机理； (3) 构建平面内各向异性纤维薄膜，揭示其机械行为响应差异化的机理。研究结果表明：在一定范围内，随着内嵌磁热转换颗粒装载量的增加，其响应速度增加，但是当装载量不足5wt%时，由于磁热转化量不足与弥补散失量，致动器无法做出反应；通过内嵌热源的方式，大大缩短了热量传递路径且纳米纤维膜的高比表面积，其响应行为可在2s内使曲率达到4 mm-1；通过改变纳米纤维膜内纳米纤维的排列方式，设计和构建平面内的各向异性，可获得方向可控的致动行为。项目研究成果可对纤维类远程隔空操控性智能致动器的设计提供理论和技术支持。