Motion Mechanism and Schooling Behavior of Visible Light Driven Nano/micromotor

Author:Zhou De Kai

Supervisor:zhang guang yu li long qiu


Degree Year:2018





Micro/nanomotor is a kind of micro/nanoscale device which can convert environmental energies into self-mechanism energy to achieve self-propulsion.With the advantages of less volume,big ratio of pushing and gravity and high specific surface area,micro/nanomotor can be widely used in the field of biomedical field,micro/nanosensing,environmental treating and cargo delivery.Among the different propulsion mechanisms,light energy is biocompatible,highly efficient and easily switched on and off which make it to be a research hotspot.However,Most of the photo-driven micro/nanomotors reported to date are activated either by UV or NIR light,which only account for 4%of the natural light,and move in the specific solvent,e.g.H2O2.These properties limit their utilities,especially in environmental applications.In addition,as the single micro/nanomotor is micro/nanoscale,its load capacity and effect is restricted which limit its application in large scale.So in this thesis,from the physical and chemical properties of semiconductor and metal,the researcher takes the light driven micro/nanomotor as object focuses on the motion mechanism and schooling behavior of visible light-driven micro/nanomotor.Based on the P type oxide semiconductor Cu2O and N type oxide semiconductor Fe2O3,two visible light-driven Cu2O/Au and Fe2O3/Au micromotor are synthesized by the chemical method,physical vapor deposition and membrane electrodeposition technique.The influences of oxide semiconductor characterizations are tested by experimental method and the effect of light intensity,solution concentration are checked.In addition,based on the electrochemical test method,motion mechanism of light driven oxide semiconductor micromotor is analyzed systematically.The study shows that the motion mechanism is light induced self-electrphoresis and the change of light resistance and photovoltage are the two key factors.Furthermore,the type of oxide semiconductor can affect the motion direction.Based on the metal-semiconductor contact theory,a metal-semiconductor-metal model is proposed and the influence of metal characterizations is analyzed.The study shows that the difference of fermi levels between metal and semiconductor is the key point for the motion.For P type semiconductor micro/nanomotors,the micro/nanomotor moved towards to the bigger difference in fermi levels.For P type semiconductor micro/nanomotors,the micro/nanomotor moved towards the smaller difference in fermi levels.Based on the light-induce diffusiophoresis mechanism,the schooling behavior of semiconductor nanoparticles in light field is studied and a light driven patterning self-assembly method is proposed.With the experimental and simulated method,the properties of local electric field and fluid are analyzed.Finally,a HIT pattern which line width is 30μm is achieved by this method.By combined acoustic and light field,a light/ulrasound driven method is proposed to control the schooling behavior of micro/nanomotors.At the same time,experimental and simulated methods are utilized to analyse the schooling/diffusion behaviors.The effects of light intensity,aouctic power and materials properties are tested systematically.In addition,diffusion position and direction control method are proposed which provide theoretical basic and technical assistance for further applicaions of micro/nanomotors cluster.In summary,this thesis carries out in-depth study on the motion mechanism and schooling behavior of light driven micro/nanomotors.These studies provide theoretical basic and technical assistance for further applicaions of micro/nanomotors on environmental treatment,biomedical field and micro/nano sensing.