Self-assembly microfabrication of multilayered helical nanomembrane and its application as microswimming robots

Official URL: https://risc01.sabanciuniv.edu/record=b258386_(Table of contents)

Microswimming robots are promising agents in biomedical disciplines due to their various potential functionality such as targeted drug delivery and microsurgery. This dissertation is dedicated to three main areas: (i) development of a self-assembly micro-fabrication technique to generate micro-scale, non-crystalline, multilayer, magnetic and helical nanomembranes; (ii) modeling and simulation; and (iii) magneto-acoustic propulsion. A thin film of nickel is sandwiched between two silicon nitride nanolayers with internal strain mismatch. Two methods of fabrication are proposed to determine the direction of rolling. The first one is changing the width-to-length aspect ratio and thickness, and the second one is topological modifications by grating the top layer of the tri-layer composite. The process of rolling from a 2D ribbon to a 3D shape is modeled by COMSOL V5.6. by moving boundary conditions inspired by the real rolling process. The results are compared and validated by experimental data with an error of less than ten percent for all cases. Near-wall swimming of the fabricated microrobots is characterized inside a cuboid reservoir filled with isopropyl alcohol by means of a rotating magnetic field. The effects of vibration are studied by using a piezo transducer next to the reservoir. The results show a maximum swimming velocity of 125 μm/s, which is improved to 250 μm/s under 1 kHz vibration frequency."}