The Electrochemical Preparation Of Mental Microrod Containing Fe₃O₄ Nanoparticle And The Study Of Its Locomotion In The Microchannel

Metal microrod can change into micro/nano machine under certain conditions,which can convert environment’s energy such as chemical energy,heat energy,magnetic energy and sound energy into autonomous motion,so it also known as micromotor.Among many self-propelled micromotors,ultrasound propelled motors are considered a leading candidate for biomedical applications,due to their good biological compatibility,low equipment requirement,low particle shape requirement and fast speed.At present,self-acoustophoresis is the most recognized mechanism for ultrasound propulsion of nanomotors,but the motion of the ultrasound-propelled micromotors is very complex.In order to better understand the movement of ultrasonically propelled motors,Au micromotor of 300 nm diameters was prepared by the template-assisted electrochemical deposition method,and then the speed of ultrasound propelled Au micromotors under different ultrasonic frequencies and voltages was researched.The results show that the speed of motors increases with the frequency,reaching a peak speed at the resonance frequency,then decresses as frequency is increased beyond the resonance frequency.Motor speed and ultrasound frequency show liner relationship.On the other hand,the speed of ultrasound motors increases quadratically with increasing applied voltage.In addition,direction control of micromotors is also a research hot topic.In this thesis,Fe3O4 nanoparticles of 15 nm diameters were synthesized by coprecipitation method.By chemical absorption of cysteamine on the surface of Au microrod to obtain positive charge,then through electrostatic absorption of negative charged Fe3O4 nanoparticles that were modificated by citric acid to prepare direction controllable magnetic micromotors.The research of the magnetic performance of the magnetic micromotor which was prepared by p H adjustment was done,and it turns out that the micromotor can be well controlled.Magnetic micromotors in biologically relevant environments have been studied to lay a solid foundation for future application.In this thesis ultrasound-propelled magnetic micromotors’ performance were examined in different salt concentration solutions,different viscosity solutions and different p H value solutions.The experimental results show that the magnetic micromotors can mvoe effectively in all kinds of biomimetic solutions.We then placed the micromotos into microfluidic channels that mimick blood vessels.These polydimethylsiloxane(PDMS)microfluidic channels were fabricated using conventional soft lithography techniques.Channels made of kapton tape were also made as comparison.Micromotors were successfully propelled by ultrasound in microfluidic channels,and their motion behavior was studied.Moreover,our experiments found that magnetic micromotors can be propelled by ultrasound in microfluidic channels and steered by magnetics effectively.In summary,we prepared a new type of magnetic micromotor,fabricated two kinds of microfluidic channels,and examined the magnetic micromotors’ movement in biomimetic solutions as well as in microfluidic channels.The results of this thesis improved the understanding of the ultrasound propulsion menchanism,and laid a solid foundation for the future biomedical applications of magnetically guided ultrasound micromotors.