Chapter 7 - Control of three bead achiral robotic microswimmers

Abstract

Miniaturized robotic swimmers are useful for navigating and performing tasks at micro- and nanoscales. Their realization can revolutionize minimally invasive procedures, for instance, micro- and nanoswimmers can navigate the human body to unclog arteries or delivery drug to solid tumors. The achiral microswimmers, in particular, can be used synergistically with particulate drug delivery systems due their self-assembling fabrication using simple magnetic particles. The achiral microswimmers can swim in bulk fluid and are controlled wirelessly via magnetic fields. One of the cores in developing micro- and nanoswimmers is to use automatous control to improve navigation capability and functionality. To demonstrate effective control over microswimmers, feedback control of the three-bead achiral microswimmers was demonstrated in experiment. This chapter will examine the properties and swimming characteristics of the achiral microswimmer, including the physical properties, hydrodynamics, and kinematics. Constraints and uncertainties will also be closely examined in order to develop a stochastic kinematic model and a nonlinear feedback controller. Uncertainties due to environmental factors such as Brownian motion and unsteady flow conditions are prominent issues to consider for velocity compensation. Finally, this chapter will discuss the successful navigation of achiral microswimmers from any initial conditions to a target position using the feedback controller.