壁虎类生物黏附系统自清洁机理的仿生研究

It is known that the adhesion systems of gecko-like creatures have not only strong attachment but also superior self-cleaning ability. But how to coordinate the two mechanics phenomena which seems contradict with each other has not been studied till now. The main motivation of the present project is to disclose the self-cleaning mechanism of the biological adhesion system and clarify the coupling relationship between the self-cleaning and strong attachment behaviors by systematically experimental and theoretical investigations. Firstly, experiments of biological and bio-inspired surfaces adhering on different substrates and in different environments are carried out systematically. The static and dynamic mechanics behaviors of the adhesive interface are observed and compared in situ. Secondly, according to the experiments, theoretical models are established to disclose the self-cleaning mechanism of biological and bio-inspired adhesion system by considering the effects of loading mode, hierarchical structure, as well as size and surface effects of the micro-structures, on the dynamic response and self-cleaning mechanism. Finally, the multi-scale mechanics method is adopted to analyze the factors that influence the unification of the surface self-cleaning and strong attachment. Combining the existing studies on the macro- and micro-adhesion mechanism of gecko, we can deeply understand the excellent strategy of gecko-like creatures that can achieve the self-cleaning and strong attachment mechanisms simultaneously. The derived results of the present project can not only provide theoretical foundation for the design of the reusable advanced synthetic adhesives and the adhesion system of bio-inspired micro-climbing robots, but also is useful for the development of biomimetic mechanics and surface/interface mechanics.

壁虎类生物的黏附系统不仅拥有超强黏附能力，同时具有优越的自清洁功能。如何协调这两个看似矛盾的力学现象目前还鲜有探索。本项目旨在通过系统的实验和理论研究，揭示生物黏附系统的自清洁机理，给出自清洁与强黏附耦合协调的物理关联。首先，系统开展生物及仿生表面在不同环境及不同基底上的黏附实验，实时在位观察及对比黏附界面的静态和动态力学行为；其次，建立与实验相应的理论模型，系统分析加载方式、结构的多级特性、微结构尺寸及表面效应对黏附表面动态响应及自清洁功能的影响，揭示壁虎类生物黏附系统及仿生表面的自清洁力学机理；最后应用多尺度力学方法，综合分析表面自清洁和表面黏附协调统一的关键因素，结合已有对壁虎类生物宏微观黏附机制的研究成果，全面理解壁虎类生物同时实现自清洁和强黏附的优异策略。研究成果能为多次重复使用的新型智能黏附材料及仿生爬壁机器人黏附系统的设计提供理论指导，并能推进仿生力学和表/界面力学的发展。

壁虎不仅具有超强黏附性能，同时具有优异的自清洁性能。针对这一现象，本项目首先系统实验研究了仿生微结构阵列表面通过微颗粒与基底的黏附行为，主要考虑了颗粒大小、微结构尺寸、压入深度等因素对仿生表面自清洁性能的影响。研究发现当压入深度较小时，仿生表面的自清洁效率均较低，与颗粒大小无关，当压入深度较大时，颗粒大小对仿生表面自清洁效率影响较大，当颗粒尺寸大于微结构间距时，自清洁效率随着压入深度的增大而增加，当颗粒大小小于或与微结构间距相当时，仿生表面自清洁效率均较低。进一步研究了基底应变梯度输运纳米颗粒的机理，发现由于应变梯度的存在，将产生作用在石墨烯滑块和碳纳米管上的非平衡作用力（矩），当该非平衡驱动力作为驱动力，将驱动石墨烯滑块滑动或碳纳米管滚动，并且驱动力随着应变梯度的增大而增大，理论结果与相应的分子动力学模拟结论一致。针对实验发现的壁虎黏附力受环境温度影响这一现象，研究了环境湿度和温度耦合作用对壁虎黏附性能的影响。当环境相对湿度不受控制时，由于相对湿度随着环境温度的改变而发生改变，进而影响界面黏附力的变化，界面撕脱力随温度的升高而降低；当相对湿度保持不变时，撕脱力对温度并不敏感，基本保持为常数。进一步实验实现了磁场调控下表面微柱变形大小和方向的有效调控。当磁场方向保持不变时，微柱变形的大小与磁场强度相关，且随磁场强度的增强微柱变形增大；当磁场强度一定时，可以通过改变磁场方向实现微柱变形方向的控制。基于能量原理，建立了磁场强度与微柱变形间的定量关系，解析得到微柱的变形形貌。并且随磁场强度增强，微柱弯曲变形增加，界面黏附力减小，合理解释了实验发现的外界磁场调控界面黏附性能的现象。拓展了经典Kendall撕脱模型，解析得到了有限长薄膜全过程撕脱行为，根据最大撕脱力与稳态撕脱力的不同，提出了一种简单、有效的界面强度和界面韧性预测方法，发展了薄膜-基底系统界面力学。