Wang Duorui, Liu Tianci, Tian Hongmiao, Zhang Jinyu, He Qiguang, Li Xiangming, Wang Chunhui, Chen Xiaoliang, Shao Jinyou
Micro-and Nano-Technology Research Center, State Key Laboratory for Manufacturing Systems Engineering, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
Advanced Electronics Research Center, Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
Proc Natl Acad Sci U S A. 2025 May 6;122(18):e2423039122. doi: 10.1073/pnas.2423039122. Epub 2025 Apr 29.
Reptiles in nature have evolved excellent adhesion systems to adapt to complex natural environments, inspired by which high-performance bioinspired dry adhesives have been consistently created by precisely replicating the natural structures. Stiffness gradient, as a special feature evolved in reptilian adhesion systems, offers significant advantages in enhancing adhesion adaptation and stability. However, it remains a challenge to accurately replicate the geometrical morphology and soft-rigid composite properties of stiffness gradient structures, which limits the engineering applications of bioinspired adhesives. Here, a stiffness gradient adhesive structure with mushroom-shaped morphology via electrically activated one-step growth is proposed. Under the action of electric field, the liquid-phase polymer grows rheologically to realize the mushroom-shaped structural morphology, and the nanoparticles inside the polymer are aggregated toward the top by dielectrophoresis to realize the stiffness gradient distribution of rigid top and soft bottom. Due to the adaptation of the soft part to the interfacial contact and the effective inhibition of peeling by the rigid part, the proposed stiffness gradient structure improves the adhesion strength by 3 times in the parallel state and by 5 times in the nonparallel state compared to the conventional homogeneous structure. In addition, the application of adhesive structures in wall-climbing robots was demonstrated, opening an avenue for the development of dry adhesive-based devices and systems.
自然界中的爬行动物已经进化出了出色的粘附系统，以适应复杂的自然环境。受此启发，人们通过精确复制自然结构，不断创造出高性能的仿生干粘合剂。刚度梯度作为爬行动物粘附系统中进化出的一个特殊特征，在增强粘附适应性和稳定性方面具有显著优势。然而，精确复制刚度梯度结构的几何形态和软硬复合特性仍然是一个挑战，这限制了仿生粘合剂的工程应用。在此，提出了一种通过电激活一步生长形成的具有蘑菇状形态的刚度梯度粘合剂结构。在电场作用下，液相聚合物通过流变学方式生长，实现蘑菇状结构形态，聚合物内部的纳米颗粒通过介电泳作用向顶部聚集，实现顶部刚性和底部柔软的刚度梯度分布。由于柔软部分对界面接触的适应性以及刚性部分对剥离的有效抑制，与传统的均匀结构相比，所提出的刚度梯度结构在平行状态下的粘附强度提高了3倍，在非平行状态下提高了5倍。此外，还展示了粘合剂结构在爬壁机器人中的应用，为基于干粘合剂的设备和系统的发展开辟了一条道路。
