ISSN   1004-0595

CN  62-1095/O4

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熊健, 王彦斌, 吕阳, 姬忠莹, 张晓慧, 王晓龙, 李志强. 环氧树脂-水凝胶软硬复合表界面各向异性摩擦研究[J]. 摩擦学学报, 2024, 44(3): 1−10. doi: 10.16078/j.tribology.2023015
引用本文: 熊健, 王彦斌, 吕阳, 姬忠莹, 张晓慧, 王晓龙, 李志强. 环氧树脂-水凝胶软硬复合表界面各向异性摩擦研究[J]. 摩擦学学报, 2024, 44(3): 1−10. doi: 10.16078/j.tribology.2023015
XIONG Jian, WANG Yanbin, LYU Yang, JI Zhongying, Zhang Xiaohui, WANG Xiaolong, LI Zhiqiang. Anisotropic Friction of Epoxy-hydrogel Based Surfaces with Soft-Hard Combination[J]. Tribology, 2024, 44 (3): 1−10. doi: 10.16078/j.tribology.2023015
Citation: XIONG Jian, WANG Yanbin, LYU Yang, JI Zhongying, Zhang Xiaohui, WANG Xiaolong, LI Zhiqiang. Anisotropic Friction of Epoxy-hydrogel Based Surfaces with Soft-Hard Combination[J]. Tribology, 2024, 44 (3): 1−10. doi: 10.16078/j.tribology.2023015

环氧树脂-水凝胶软硬复合表界面各向异性摩擦研究

Anisotropic Friction of Epoxy-hydrogel Based Surfaces with Soft-Hard Combination

  • 摘要: 由取向微结构引起的各向异性摩擦学是生物系统中最常见的引起摩擦形式之一. 而研究表明,软硬复合的生物表界面在获取各向异性摩擦力时更具有优势. 因此,本研究中以最典型的钩状倒刺微结构为研究对象,结合3D打印先进制造技术,通过在仿生取向微结构表界面原位复合低模量的水凝胶材料,获得环氧树脂-水凝胶软硬复合表界面. 研究结果表明,水凝胶在Fe3+溶液中的配位交联6 h时,其模量为3.6 MPa,相对于环氧树脂(模量为13.6 MPa)为软材料. 在5 N载荷下,仿生表界面正方向摩擦力为1.64 N,反方向摩擦力为3.44 N,其各向异性摩擦力最大差值可达1.80 N. 本研究中对软硬复合的生物表界面具有一定的理论指导意义,有望在智能摩擦调控和软体机器人等方面发挥一定的作用.

     

    Abstract: Anisotropic friction caused by oriented microstructure is one of the most common causes in biological systems. Typical examples like the snake locomotion with the aid of highly ordered fiber-like microstructures in ventral body side, the wheat awns propel the seeds on and into the ground with the help of silicified hairs that cover the awns, and the tree frogs have excellent wet attachment and friction performance can freely and repeatedly climb on vertical surfaces or overhang with the help of hierarchical pillar arrays. It has been demonstrated that the biological surface of soft-hard combination exhibits the more advantages for obtaining the anisotropic friction force, especially for the combination of hard structure and soft substrate. Even though the research of anisotropic friction based on the surface microstructures has obtained significant progress, the complicated preparation method, the little-span of modulus variation, and the unobvious switching of friction force are still limited the development of this project. Therefore, the hook-like spines, as one of the most effective topographies from various plants and animals for generating anisotropic force, were employed in this study. Furthermore, take advantages of additive manufacturing with the merits of creating sophisticated, bespoke and low-cost materials/devices, the surface with hook-like spines was prepared by a digital light process (DLP) 3D printer. And the optical microscope images displayed the printed surface was covered with hook-like spines exhibiting the same orientation and morphology, which were necessary for exploring the anisotropic friction force. In addition, for mimicking the typical combination of soft-hard combination and obtaining the dynamic friction force, the low modulus hydrogel was grown in-situ on the bionic oriented microstructures. To further enhance the mechanical performances, the prepared epoxy-hydrogel samples were immersed in Fe3+ solution for a secondary crosslinking by ionic coordination. The results demonstrated that with the increase of secondary cross-linked time, the hydrogel had an increased modulus. Integrating with the element of ruptured strain, the immersed time of 6 h was chosen with the modulus of 3.6 MPa and the ruptured strain of 288%. Comparing with epoxy resin, whose modulus was 13.6 MPa, the enhanced hydrogel was still a soft material. Finally, the anisotropic friction force of the prepared biomimetic epoxy-hydrogel surface under different conditions were investigated. Typically, when the normal load was increased from 1 N to 5 N, the negative friction force was greater than that of the positive friction force gradually. Importantly, with the normal increasing, the corresponding anisotropic friction force exhibited the larger difference. For example, under the 5 N load, the positive friction force of the biomimetic epoxy-hydrogel surface was 1.64 N, while the opposite sliding direction was 3.44 N, which showed the largest anisotropic friction difference. In this way, we demonstrated the prepared soft-hard surface had an isotropic friction force between positive and negative sliding directions at the lower normal load, while the friction force became anisotropic with the normal load increasing (>4 N). This study had a certain theoretical significance for the biological surface with the soft-hard combination, and was expected to play a certain role in intelligent frictional control, smart actuators and microbots, and some other friction-induced/controlled devices.

     

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