Characterizing the Swimming Properties of Artificial Bacterial Flagella

Abstract

Artificial bacterial flagella (ABFs) consist of helical tails resembling natural flagella fabricated by the self-scrolling of helical nanobelts and soft-magnetic heads composed of Cr/Ni/Au stacked thin films. ABFs are controlled wirelessly using a low-strength rotating magnetic field. Self-propelled devices such as these are of interest for in vitro and in vivo biomedical applications. Swimming tests of ABFs show a linear relationship between the frequency of the applied field and the translational velocity when the frequency is lower than the step-out frequency of the ABF. Moreover, the influences of head size on swimming velocity and the lateral drift of an ABF near a solid boundary are investigated. An experimental method to estimate the propulsion matrix of a helical swimmer under a light microscope is developed. Finally, swarm-like behavior of multiple ABFs controlled as a single entity is demonstrated.

Propulsive force measurements and flow behavior of undulatory swimmers at low Reynolds number

“…One of the leading avenues of such research has been in the use of magnetic fields to actuate artificial bioinspired helical structures in fluids. [19][20][21][22] Alternatively, a number of studies have focused on the collective behavior of bacteria swarm, both experimentally [23][24][25][26][27] and theoretically. 23,[28][29][30][31][32] Investigations have shown that bacterial suspensions develop transient patterns of coherent locomotion with correlation lengths much larger than the size of individual organisms.…”

Magnetic Actuation Based Motion Control for Microrobots: An Overview

“…The microrobot is steered in the horizontal plane by a uniform magnetic field. As for helical swimmers actuated by a rotating magnetic field, researchers estimate the rotation direction of the field; for example, a rotating magnetic field with a fixed rotation axis to actuate the helical swimmer to follow a straight line [36,40,73]. Then, Ghosh et al [37] achieved following a curved trajectory (e.g., "R@H") with their helical microrobots, which were navigated by a pre-programmed controller to actuate the magnetic field.…”

Mini and Micro Propulsion for Medical Swimmers

“…More specifically, the bubble type (putt-putt boat type) swimmers are using momentum transfer through the microstreaming formed by bubble oscillation [19,20]. The micro robots that harness natural organisms or use the artificial cilia/flagella (regardless of motion types, corkscrew motion, or flexible oar motion) generate propulsion via viscous stress interaction [17,18,[21][22][23][24][25][26]. Among the chemical micro swimmers, even though there are still debates on the mechanism [27], some devices utilize the bubble recoiling method to make momentum transfer by inertia propulsion [28][29][30][31].…”

“…Leoni et al [40] first realized this model experimentally with optical tweezers and compared the experimental results with the numerical solution. [19], 1′-acoustic scallop (Re is based on oscillating speed and amplitude), 2-oscillating micro bubble (Re is based on body speed and size) [20], 2′-oscillating micro bubble (Re is based on oscillating speed and amplitude), 3-artificial magnetic bacteria flagella [21], 4-artificial magnetic nanostructured propeller [22], 5-magnetically actuated colloidal [23], 6-magnetotactic bacteria propeller [24], 7-flagella-based propulsion [25] [17], and 19-Escherichia coli [18]. Note that the triangles denote inertia dominant propulsion, the squares denote viscous dominant propulsion, and the circles means the propulsion mechanisms cannot be clearly classified.…”

“…The model took into account the effect of the head, the magnetic field strength and the rotation frequency. The maximum velocity of ABF reached about 18 μm/s, and the propulsion force was calculated to be about 3.0 pN [21]. For similar swimming robots but several millimeters in size, more experiments in both water and glycerin were performed to compare the inertia and viscous forces [61].…”