טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentGabor Kosa
SubjectMicro Robots for Medical Applications
DepartmentDepartment of Mechanical Engineering
Supervisors Full Professor Shoham Moshe
Professor Zaaroor Menashe


Abstract

The ideal micro robot for medical applications is a totally autonomous one that is able to position itself and perform medical manipulation within the human the body. Such a system is a distant goal of research, but several micro medical devices have already been developed that posses some robotics aspects such as micro catheters, smart pills and swimming micro robots.

This scientific research work concentrates on swimming micro-robots that can serve as a platform for next generation un-tethered endoscopes for transmitting images from inside the human body.

The specific medical task considered in this study is endoscopy of the spinal subarachnoid space. We found that the morphology of the subarachnoid space limits the diameter of an endoscope or a swimming micro robot to be up to 2.5 mm.

In order to create swimming in a space confined by geometrical limitations of the subarachnoid space one has to take into consideration the low Reynolds number hydrodynamics. Inspired by natural Stokes flow swimmer, a novel propulsion theory based on flagellar motion has been developed. The propulsion was achieved by creating traveling wave along a tail made of piezoelectric material decomposed into the natural modes of the beam. The coupled electric-elastic-fluidic problem was solved analytically. The traveling wave is created by dividing the piezo-electric actuator into several segments and applying on each segment a sinusoidal voltages with the same frequency and different phases and amplitudes.

The propulsive velocity of the swimming tail was found by extending G.I. Taylor's earlier work to a non-circular cross-section.

The propulsive theory was validated experimentally and matched closely the theoretical results. The developed propulsion theory was verified by an experimental system using a commercial 35 mm long 2.5 mm wide piezoelectric actuator divided optimally into three segments. Hanging the model dipped into high viscosity gear oil from 2 m height enable measuring of the propulsive force which is proportional to distance travel The tail achieved displacement of 8 mm which is equivalent to propulsive force of 40 [μN] - 15 % lower than the theoretical data.