Swimming Behaviour of a Sperm-Flagella Driven Micro-Bio-Robot: From Fundamental Studies to Biomedical Applications

混合微游泳器是一种利用生物动力源驱动人工合成微结构的微游泳器，是实现小尺度可控驱动的一种有效途径。特别是，生物游泳者提供了一个生物相容性的解决方案，在低雷诺数制度的运动和货物输送。我们的方法，以混合microswimmer由铁磁纳米膜卷成微管和捕获单牛精子。单个运动细胞能够推动卷起的微管向前，而外部磁场可以用于引导精子鞭毛驱动的微型生物机器人到期望的位置。正如我们的项目名称所揭示的，这项工作的目的是，一方面更深入地了解精子在微管中的运动，另一方面逐步走向精子驱动的微型生物机器人有希望的生物医学应用。该项目的基础研究的主要目标是了解精子驱动的微型生物机器人在更现实的环境中的生物物理动力学。这包括较高粘度的介质、非牛顿流体和在精子的自然环境中以及通常在体液中给出的其他条件。此外，我们将研究刺激对精子驱动的微型生物机器人的影响，并探索其作为控制机制的适用性。出租车机制，如rheotaxis（方向对流体流动）和thigmotaxis（与表面的相互作用）将是我们调查的重点。特别有趣和具有挑战性的出租车为基础的上下文中将是精子驱动的微型生物机器人的不同控制机制的相互作用。例如，什么是最小的磁场强度需要推翻rheotactic方向，精子驱动的微型生物机器人将重新定向后，磁场被关闭？这些问题和其他问题将在本项目的这一部分得到解决。此外，我们计划研究精子驱动的微型生物机器人与卵丘细胞层的相互作用，卵丘细胞层是精子在进入卵母细胞的途中遇到的粘性细胞层。将对微管进行表面修饰，以局部降解卵丘细胞并释放通向卵母细胞的通道。将探索精子驱动的微型生物机器人作为活性药物载体的潜力。总之，这将导致重要的进展，在精子运动的基本理解，但也有助于精子驱动的微型生物机器人在辅助生殖或药物输送的应用。

Hybrid microswimmers which contain a biological power source for the propulsion of artificially synthetized microstructures is an appealing approach for the controlled actuation on the small scale. In particular, biological swimmers offer a biocompatible solution for the motion and cargo delivery in the low Reynolds number regime. Our approach to a hybrid microswimmer consists of ferromagnetic nanomembranes which roll up into microtubes and capture single bovine spermatozoa. The single motile cell is able to propel the rolled up microtube forward while an external magnetic field can be used to guide the sperm-flagella driven micro-bio-robot to desired locations. As our project title reveals, the aim of this work is, on the one hand to gain a deeper understanding of sperm motion in the confinement of microtubes, on the other hand to go step by step towards biomedical applications which the sperm-driven micro-bio-robots are promising for. The main goal of the fundamental studies of this project is to understand the biophysical dynamics of sperm-driven micro-bio-robots in more realistic environments. This includes higher viscosity media, non-Newtonian fluids and other conditions that are given in the natural surroundings of spermatozoa and also in general in body fluids. Furthermore, we will investigate the influence of stimuli on the sperm-driven micro-bio-robots and explore their suitability as control mechanisms. Taxis mechanisms such as rheotaxis (orientation against fluid flow) and thigmotaxis (interaction with surfaces) will be in the focus of our investigations. Especially interesting and challenging in the taxis-based context will be the interplay of the different control mechanisms of the sperm-driven micro-bio-robots. For instance, what is the minimum magnetic field strength needed to overrule the rheotactic orientation, will the sperm-driven micro-bio-robot reorient in the flow after the magnetic field is turned off? These and further questions will be addressed in this part of the project. Furthermore, we plan to study the interaction of the sperm-driven micro-bio-robots with the cumulus cell layer, which is a viscous cell layer which the spermatozoa encounter on their way to the oocyte. Surface modifications of the microtubes will be implemented in order to degrade the cumulus cells locally and free the way to the oocyte. The potential of the sperm-driven micro-bio-robots to serve as active drug carriers will be explored. In summary, this will lead to important progress in the fundamental understanding of sperm motion but also be helpful towards applications of the sperm-driven micro-bio-robots in assisted reproduction or drug delivery.