|Ph.D Student||David Zarrouk|
|Subject||The Interaction between Micro-Robots and Biological Tissues|
|Department||Department of Mechanical Engineering||Supervisor||Full Professor Shoham Moshe|
|Full Thesis text|
An inherent characteristic of biological vessels and tissues is that they exhibit significant flexibility both in the normal and tangential directions. The latter, in particular, is atypical of standard engineering materials and presents additional challenges for designing robotic mechanisms for crawling along the tissue of biological vessels. Several studies aimed at designing and building worm-like robots to move within the human body have been carried out but little was done on analyzing the interactions between the robots and their flexible environment. In this study, the interaction between worm-like robots and the biological tissues is analyzed, in terms of locomotion efficiency and condition of locomotion of the robot as function of the robot and flexible surface parameters. The locomotion behavior is studied both when the deflections are local to the cells (local analysis) and when the deflections of the different cells are dependant (structural analysis). The first type of analysis is mainly applicable to blood vessels, urinary tract and respiratory tracts and the latter is mainly applicable for intestine like environment.
Unlike what has been proposed by previous studies, it was found that the tangential flexibility has an additive effect on the locomotion efficiency. The deflections under the different cells of the worm were found to form an arithmetic series during locomotion. Using the two previous conclusions, an explicit formulation of the locomotion efficiency (the ratio of the actual advance divided by the stroke) for the “local compliance” is derived as a function of the tangential flexibility, friction coefficients, number of cells in the robot, contact and external forces acting on the robot. This derivation allows the designer to find the conditions of locomotion of the worm robots as well as it allows him to decide on the number of necessary cells, size of the stroke and the grasping mechanisms and forces.
The analytical results and simulations were experimentally verified using in-house designed worm robots which moved along locally and structurally flexible synthetics surfaces with predesigned compliance values.
The earthworm and inchworm locomotions were proven in this study to have a single degree of freedom. This allows the design of unique worm robots actuated by a single motor. This design allows for significant miniaturization and reduces complexity and cost. The design of the robot and analysis of its dynamics and power efficiency are described. In this work, two earthworm and inchworm prototypes were built to demonstrate its performance.