Locomotion of Microrobots Driven by Different Surface Velocities in Complex Fluids

Over the past few decades, microrobots have rapidly evolved. Given their tiny size, microrobots can access all body regions to facilitate targeted therapies and diagnostics, having great potential in biomedical engineering and biomedicine. While most previous demonstrations of microrobots typically considered a homogeneous Newtonian fluid as the medium, the reality of the biological environment is much more complex, with many biological fluids displaying complex non-Newtonian properties including viscoelasticity and shear-thinning viscosity. The squirmer model is a popular and generalized swimmer model for motions in non-Newtonian fluid, where the swimming velocity is generally given by the surface average of the prescribed velocity. To further explore the effects of neglected surface velocity details and shear-thinning properties on the motions of microrobots in non-Newtonian fluids, a simulation framework was proposed for studying the kinematic performance of robots in complex fluids. The effects of shearthinning properties on the kinematic performance of microrobots with different surface velocity distributions were also investigated. Furthermore, the threshold value of the magnetic moment applied to the robot when it is not deflected was also discussed. The design of different types of surface velocities for microrobots involved in this paper can better guide more efficient propulsion of microrobots in complex biofluids.