The Study Of The Efficiency Enhancement Of Light-driven Micromotors Via Synergistic Effect

In recent years,micromotors have attracted increasing academic attention due to their widespread applications in drug delivery,biosensing,and environmental remediation.Light-driven micromotors convert light,a source of clean energy,into mechanical motion,and is of great significance due to its broad applicability in the studies of soft matter and active materials,and wide applications in biomedicine and environmental remediation.Among the many designs of light-driven micromotors,those powered by photocatalytic reactions are particularly worth noting.However,earlier studies have shown a low energy conversion efficiency for catalytic micromotors,giving rise to problems such as low motor speeds and a requirement of high fuel concentrations.As a result,photocatalytic motors with higher efficiency is in urgent demand.To tackle these challenges,two methods are proposed in this thesis that improved the energy efficiency of micromotors made of titanium dioxide(Ti O2).Firstly,inspired by previous work,Ti O2-Au/Ag Janus micromotors are prepared by successively depositing gold and silver onto prefabricated Ti O2 spheres.The average speed of the resulting Ti O2-Au/Ag motors was twice as that of Ti O2-Au Ti O2-Ag motors.Based on electrochemical measurements,we speculate that this enhancement in speeds is due to a synergy between the two metals,gold and silver.The presence of these two metals promotes the catalytic activity of the motor,which results in a larger photocurrent and faster chemical reactions on the motor surface that eventually enables faster propulsion.Besides,the recent introduction of hybrid motors is expected to address the weakness of individual motors thanks to the ability to simultaneously drive a motor with multiple power sources.In this thesis,we design a hybrid Ti O2-Pt micromotor by exposing it to light and electric fields simultaneously.The experiment results show that when an AC electric field is perpendicularly applied to the substrate,the speed of Ti O2-Pt motors under UV light increase immediately and significantly,suggesting a synergy between the light field and the electric field in improving the motor's performance.Subsequently,by calculating the tilting angle of a motor during its operation,we find that the speed of a motor increase with its tilting angle until reaching a maximum speed when the motor's Janus interface is perpendicular to the substrate.By using several types of motors including titanium dioxide-nickel/platinum(Ti O2-Ni/Pt),polystyrene-platinum(PS-Pt),gold-platinum(Au-Pt),and titanium-silica(Ti O2-Si O2)as control experiments,we propose that the acceleration of motors is attributed to the applied electric field that aligns the interface of motors perpendicular to the substrate,holding the tilting of the motor to be straight.To summarize,we explore two methods to improve the efficiency of photocatalytic micromotors through synergistic effects and reveal how the speed of photocatalytic motors is correlated to their tilting angles.These results pave the way for further exploring the dynamics of light-driven micromotors and for their practical applications.