School of Mechanical Engineering and Automation, Beihang University, Beijing, 100191, China.
Shen Yuan Honors College, Beihang University, Beijing, 100191, China.
Sci Rep. 2021 Nov 5;11(1):21728. doi: 10.1038/s41598-021-00902-6.
Sperm cells can move at a high speed in biofluids based on the flexible flagella, which inspire novel flagellar micro-/nanorobots to be designed. Despite progress in fabricating sperm-type robots at micro scale, mass fabrication of vivid sperm-like nanorobots with flagellar flexibility is still challenging. In this work, a facile and efficient strategy is proposed to produce flexible sperm-like nanorobots with self-assembled head-to-tail structure, and its bidirectional propulsion property was studied in detail. The nanorobots were composed of a superparamagnetic head and a flexible Au/PPy flagellum, which were covalently linked via biotin-streptavidin bonding with a high yield. Under precessing magnetic fields, the head drove the flexible tail to rotate and generated undulatory bending waves propagating along the body. Bidirectional locomotion was investigated, and moving velocity as well as direction varied with the actuating conditions (field strength, frequency, direction) and the nanorobot's structure (tail length). Effective flagellar propulsion was observed near the substrate and high velocities were attained to move back and forth without U-turn. Typical modelling based on elastohydrodynamics and undulatory wave propagation were utilized for propulsion analysis. This research presents novel artificial flexible sperm-like nanorobots with delicate self-assembled head-to-tail structures and remarkable bidirectional locomotion performances, indicating significant potentials for nanorobotic design and future biomedical application.
精子细胞可以在基于柔性鞭毛的生物流体中高速移动，这启发了新型鞭毛微/纳米机器人的设计。尽管在微尺度上制造精子型机器人已经取得了进展，但大规模制造具有鞭毛柔韧性的逼真精子样纳米机器人仍然具有挑战性。在这项工作中，提出了一种简单高效的策略来制备具有自组装头对头结构的柔性精子样纳米机器人，并详细研究了其双向推进特性。纳米机器人由超顺磁头和柔性 Au/PPy 鞭毛组成，通过生物素-链霉亲和素键合以高产率共价连接。在进动磁场下，头部驱动柔性尾部旋转，并产生沿体传播的波状弯曲波。研究了双向运动，运动速度和方向随激励条件（场强、频率、方向）和纳米机器人的结构（尾部长度）而变化。在靠近基底的地方观察到有效的鞭毛推进，并且在无需掉头的情况下可以达到高速度来回移动。基于粘弹流动力学和波状传播的典型建模用于推进分析。这项研究提出了具有精细自组装头对头结构和显著双向运动性能的新型人工柔性精子样纳米机器人，为纳米机器人设计和未来的生物医学应用提供了重要的潜力。
