סמינר מחלקתי

School of Mechanical Engineering Seminar
Wednesday, November 19, 2014 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Hydrodynamic Modeling of a Magnetic Micro Swimmer: Theory, Simulations and Experiments

Avi Friedman

M.Sc Student of Prof. Alex Liberzon and Dr. Gábor Kósa

Tel Aviv University, Israel

Capsule endoscopy is a promising technology for diagnosis and intervention and has the potential to revolutionize the biomedical field. Capsule endoscopes are gradually transforming from passive diagnostic devices into miniature self-propelled mobile robots capable of autonomous or wirelessly-controlled maneuvering. Several different implementations are currently under development. The swimmer researched herein uses two small solenoids with alternating sinusoidal current and the constant magnetic field of an MRI (Magnetic Resonance Imaging) machine to create an undulating motion that propels the capsule. This can be used in the future, together with the MRI as an accurate diagnostic tool, in order to achieve both a real-time image from the MRI and a locally-targeted intervention or observation from the capsule endoscope.

One of the main challenges in developing such devices is to understand the external flow phenomena that occur as the device propels itself, and to understand the forces the device is subjected to, in order to be able to predict the power requirements of such device.

A model was developed using the Lagrangian dynamics to find numerically the motion of the magnetic swimmer. The dynamic model was compared to PIV (Particle Image Velocimetry) experiments to achieve a full map of the velocity field that is created by the micro swimmer, and to derive the forces acting on the swimmer by integrating along a closed loop around the swimmer. The results were used to validate the model, where the forces were indirectly measured by finding the deflection of the swimmer from equilibrium. We found that for a driving current with amplitude of 10V the propulsive force was 0.033 mN for a Reynolds of 44 and 0.071 mN for a Reynolds of 700. The PIV experiment showed similar results.