M.Sc Thesis

M.Sc StudentMirzae Yoni
SubjectStochastic Shape Optimization and Numerical Modeling of
Magnetic Microrobots
DepartmentDepartment of Applied Mathematics
Supervisors PROF. Alexander Leshansky
DR. Konstantin Morozov


Recent technological advances in micro- and nanoscale fabrication techniques allow for the construction and development of both rigid and flexible micron-scale robotic swimmers that can be efficiently actuated using time-varying magnetic fields. Some of these artificial swimmers mimic locomotion strategies similar to those utilized by microorganisms to swim in an environment dominated by viscosity forces. An example for such microswimmers is the artificial magnetic chiral microhelices that are driven by a rotating magnetic field and exhibit corkscrew-like propulsion, which is commonly considered as universally efficient in viscous regime. Although chirality has been considered a necessary condition for propulsion, recent experiments demonstrated that achiral objects can propel similarly to microfabricated helical motors, what has led to the development of a general theory explaining the dynamics of magnetized rigid objects of arbitrary shape in a rotating magnetic field. In this work we apply the genetic search algorithm based on the proposed theory to determine geometries of microrobots that maximize propulsion speed under certain symmetry constraints. The algorithm results suggest that an arc-shaped object is near optimal in a class of achiral propellers, while the optimal skew-symmetric shape deviates considerably from a helix. Additionally, we present a numerical modeling of magnetic microswimmers made of spheres connected by elastic links. This model allows for the simulation of the dynamics of robotic swimmers of arbitrary and non-uniform rigidity.