Artificial bacterial flagella: Fabrication and magnetic control

Abstract

Inspired by the natural design of bacterial flagella, we report artificial bacterial flagella (ABF) that have a comparable shape and size to their organic counterparts and can swim in a controllable fashion using weak applied magnetic fields. The helical swimmer consists of a helical tail resembling the dimensions of a natural flagellum and a thin soft-magnetic “head” on one end. The swimming locomotion of ABF is precisely controlled by three orthogonal electromagnetic coil pairs. Microsphere manipulation is performed, and the thrust force generated by an ABF is analyzed. ABF swimmers represent the first demonstration of microscopic artificial swimmers that use helical propulsion. Self-propelled devices such as these are of interest in fundamental research and for biomedical applications.

The chiral magnetic nanomotors

“…The optimal value of the helix angle is in the range Θ = 35 • ÷ 45 • maximizing the chirality, Ch ≈ 0.2 (v). Despite a large variability in the nanofabrication techniques and experimental setups [4][5][6][7][8][9][10]19], it is interesting to point out that one of the pioneering experimental works in this field, [4], has empirically adopted most of the rules formulated above.…”

“…The situation has changed dramatically with the development of the fundamentally new approach to the directed transport of magnetic particles. It was demonstrated [4][5][6] that the rotating magnetic field even of small or moderate amplitude can be applied for propulsion of chiral magnetic nanoparticles. These particles are named "artificial bacterial flagella" due to their biomimetic helical shape that provides chirality necessary for propulsion [5].…”

Mini and Micro Propulsion for Medical Swimmers

“…An artificial bacteria flagella (ABF) [58,59] was developed with a square soft-magnetic metal plate head and a helical tail using the anomalous scrolling process, as shown in Figure 4b [60].The ABF with a 38-μm tail could swim forward and backward at the average speed of around 1.2μm/s by changing the rotation direction of the external magnetic field. The propulsion force of the 29-μm long ABF, which was estimated from the drag force of a single microsphere pushed by the ABF swimmer [58], was about 0.17 pN.…”

“…The propulsion force of the 29-μm long ABF, which was estimated from the drag force of a single microsphere pushed by the ABF swimmer [58], was about 0.17 pN. Later, the authors quantitatively analyzed and mathematically modeled this 6-degree-of-freedom motion in comparison with the experiments.…”

Magnetic Actuation Based Motion Control for Microrobots: An Overview

“…In this article, we focus on the magnetic actuation-based motion control of microrobots. In the literature, swimming microrobots are wirelessly propelled in a fluid environment: some of them can be pulled by a magnetic gradient [35]; some of them having helical structures are rotated by a rotating magnetic field and convert the rotation to linear displacement [36][37][38][39]. Researchers have used different magnetic actuation systems allowing differently-sized workspace and degrees of freedom (DoF).…”