Enhancing Swimming Performance by Optimizing Structure of Helical Swimmers

Enhancing Swimming Performance of Magnetic Helical Microswimmers by Surface Microstructure

Artificial bacterial flagella (ABF), also known as a magnetic helical microswimmer, has demonstrated enormous potential in various future biomedical applications (e.g., targeted drug delivery and minimally invasive surgery). Nevertheless, when used for in vivo/in vitro treatment applications, it is essential to achieve the high motion efficiency of the microswimmers for rapid therapy. In this paper, inspired by microorganisms, the surface microstructure was introduced into ABFs to investigate its effect on the swimming behavior. It was confirmed that compared with smooth counterparts, the ABF with surface microstructure reveals a smaller forward velocity below the step-out frequency (i.e., the frequency corresponding to the maximum velocity) but a larger maximum forward velocity and higher step-out frequency. A hydrodynamic model of microstructured ABF is employed to reveal the underlying movement mechanism, demonstrating that the interfacial slippage and the interaction between the fluid and the microstructure are essential to the swimming behavior. Furthermore, the effect of surface wettability and solid fraction of microstructure on the swimming performance of ABFs was investigated experimentally and analytically, which further reveals the influence of surface microstructure on the movement mechanism. The results present an effective approach for designing fast microrobots for in vivo/in vitro biomedical applications.

Natural Cilia and Pine Needles Combinedly Inspired Asymmetric Pillar Actuators for All-Space Liquid Transport and Self-Regulated Robotic Locomotion

Natural structures and motion behaviors open new avenues for effective small-scale transport, such as the plant-inspired energy-free liquid transport surfaces and cilia-inspired propulsion systems. However, they are restricted by either the fixed structure or nonself-regulating beating modes, making many complex tasks remain challenging, e.g., the controllable multidirectional liquid transport and flexible propulsion. Herein, inspired by pine needles and natural cilia, we report an asymmetric-structured intelligent magnetic pillar actuator (AI-MPA) with both the "passive" and "active" transport features. Under the control of the magnetic field, the AI-MPA shows an all-space liquid transport ability toward arbitrary directions. Moreover, benefiting from the material's magnetoelasticity and asymmetric-structured design, the AI-MPA enables self-regulation of two-dimensional (2D)/three-dimensional (3D) cilia-like beating modes and can be further developed for robotic crawling and self-rotatable motion. The AI-MPA integrates the superiority of static and dynamic systems in nature and exhibits intelligent self-regulation that could not be achieved before. Confirmed theoretically and demonstrated experimentally, this work provides insights into increasingly functional and intelligent miniature biomimetic systems, with applications from directional liquid transport to robotic locomotion.

Magnetic bio-hybrid micro actuators

Over the past two decades, there has been a growing body of work on wireless devices that can operate on the length scales of biological cells and even smaller. A class of these devices receiving increasing attention are referred to as bio-hybrid actuators: tools that integrate biological cells or subcellular parts with synthetic or inorganic components. These devices are commonly controlled through magnetic manipulation as magnetic fields and gradients can be generated with a high level of control. Recent work has demonstrated that magnetic bio-hybrid actuators can address common challenges in small scale fabrication, control, and localization. Additionally, it is becoming apparent that these magnetically driven bio-hybrid devices can display high efficiency and, in many cases, have the potential for self-repair and even self-replication. Combining these properties with magnetically driven forces and torques, which can be transmitted over significant distances, can be highly controlled, and are biologically safe, gives magnetic bio-hybrid actuators significant advantages over other classes of small scale actuators. In this review, we describe the theory and mechanisms required for magnetic actuation, classify bio-hybrid actuators by their diverse organic components, and discuss their current limitations. Insights into the future of coupling cells and cell-derived components with magnetic materials to fabricate multi-functional actuators are also provided.

Exploration of Internal and External Factors of Swimmers' Performance Based on Biofluid Mechanics and Computer Simulation

The purpose of this study is to explore the influence of different swimming strokes on the performance of swimmers and the resistance of each part from the perspective of hydrodynamics. In this paper, the influence of internal and external factors on the swimming speed is analyzed comprehensively and meticulously from the macro and micro perspectives. In the macroscopic part, the swimming speed representation model is established, and the validity of the model is further verified by the analysis of experimental data and hydrodynamic equations. In the microscopic part, we carefully analyzed details such as the opening angle of the palm, the timing of the arm and leg and the angular velocity of each link of the human body. Combined with computer simulation, stereo modeling and numerical analysis are carried out, and the best scheme FOR how to cooperate with each part of the body in swimming is given.