The Study Of Light Driven Device Motion By Photothermal Effect

This thesis reports a study of photothermally driven motion at the interface of liquid/air and in the water,respectively.The motion of light-driven device by photothermal effect at liquid/air interface always depends on liquids surface tension.In this work,we have fabricated a paper based composite membrane with assembled gold nanoparticles.Such composite membrane could be designed into boat shape and horizontally be propelled by vapor ejection generated from evaporation of localized liquid which is heated by the conversion from light to heat at liquid/air interface.It is not necessary for such a device to rely on the liquids surface tension.We explore different movement behaviors of this device and some factors influencing the motion of device.In addition,we further optimize the structure of device and design semi-sealed device.This device can reduce the diffusion of vapor into air and get a higher speed.On the other hand,it has seldom been reported that the exploration of mechanism for driving device in the vertical direction of liquid,which largely limit the application scale of light-driven device.To demonstrate the photothermally driven surfacing and diving motion,we fabricate a device with hydrophobic surface and high efficiency photothermal effect by template-dissolution method to achieve the motion in vertical direction.Light illumination could be converted into thermal energy to heat the small bubbles attached on the device.The expansion of bubbles would increase the buoyancy of device and lift device upward gradually.After turning off the light,bubbles attached on device surface are cooled by surrounding liquid and shrink gradually.Once the buoyancy of the device is smaller than gravity,device will dive to the bottom of liquid.Thus,the motion of device in vertical direction can be controlled by light illumination.The height of surfacing motion of device could also be changed through adjusting the time of light irradiation.The suspension stability of device is also explored.Furthermore,we demonstrated that kinetic energy of surfacing and diving motion could be converted into electric energy to control the light of external LEDs.These light driven devices by photothermal effect will open mind for the applications such as cargo delivery,water purification and energy conversion.