Collective Behaviors Of Micro/Nanomotors Driven By Light-Induced Diffusiophoresis

Individuals in nature exhibit complex clustering behavior,thus acquiring diverse functions.Resembling to the natural collective systems,the artificial micro/nanomotor group can form a collective group through internal interaction and environmental interaction,thus showing the function far beyond the individu al micro/nano motor.Micro/nanomotor is a micro-nano scale robot which can transform environmental energy into its own mechanical energy.Self-propelled synthetic colloid motors could be powered by different mechanisms,which correspondingly has different advantages.Light is a relatively cost-effective stimulus due to its ubiquity,remote maneuverability and precise controllability.Also based on the light-driven diffusion mechanism,light could transform gradient of light into gradient of chemical concentration at the macro level.So as to effectively solve the problem that monomer micro-nano motor cannot cope with the large-scale environmental pollution and the massive tissue lesion,micro-nano motors driven by light-induced diffusion are highly profitable.However,at present,the research of diffusion-driven micro-nano motors mainly focuses on phenomenon research,lacking in-depth explanation of internal mechanism and application-oriented cluster strategy.Therefore,the study on the propulsion mechanism and collective behavior of the light-driven diffusion micro/nanomotor can provide optimization parameters for the design of the diffusion-nano motor,which is of great significance to improve the application range and effect of the light-driven micro/nanomotor.By combining theoretical research,experimental finding and numerical simulation,internal energy band distribution of semiconductor and carrier distribution were studied firstly based on the physical and chemical properties of semiconductor.Based on the modulation effect of conductivity and mechanism of Shockley-Read-Hall recombination,conductivity variation and carrier recombination rate of ferric oxide under illumination were explored.Also,based on mechanism of thermionic emission,escape of the internal electrons in semiconductor escape was also illustrated.According to the photo-Fenton reaction between iron oxide and hydrogen peroxide,the composition of reaction products and the influence of PH value on product components were explained.Based on electrochemical principle,the influencing factors of ion exchange rate of surface reaction were revealed.Based on the theory of double electric layer and Boltzmann distribution,the effects of the physical characteristics of the motor surface and the chemical characteristics of the solution on the interaction between the motor and the solution were analyzed.The governing equations of each physical field module in solution environment were clarified,and the unidirectional coupling relations between physical fields were analyzed according to the governing equations.A fully coupled model toward diffusion of micro-nano motor in solution was established.According to the single-medium solution environment,an experimental device was designed to make the nanoparticles patterned.Iron oxide micro-nano particles were prepared by high temperature hydrothermal method.Morphology,size,crystal phase,elements and light absorption characteristics of these particles were characterized.The collective patterning behavior of micro/nanomotors under illumination were studied experimentally.A fully-coupled finite element model for the patterning behavior of micro/nano motor was established.Multiple physica l field including reaction engineering,chemistry,static electricity,fluid and particle tracing multiple were employed to study the collecting behavior of motors.Distribution of concentration,electric field,streamline of fluid and configuration of particles were studied based on the full-coupled model.In order to widen the application range of micro/nanomotors in the field of micro-nano manufacturing,the edge sharpness of the pattern with regard to various parameters were explored.According to the two-phase solution environment,a droplet robot driven by a group of micro/nano motors was designed based on the mechanism of light-induced diffusion.Moving behavior of liquid droplets loaded with hydrogen peroxide solution and nanomotors under illumination was studied.In order to realize the reconfiguration nanomotors to control the dynamic motion of droplets,multiple droplets were integrated by changing the light source.Based on the multi-physical field model of light-induced diffusion above,the model was further coupled to the two-phase flow.Variation of the two-phase interface before and after illumination were explored.In order to widen the application range of micro/nanomotors in the field of micro/nano transportation,velocity of the droplet with regard to forward reaction rate,radius of particle and mobility of two-phase were studied..