Fabrication Optimization And Mechanism Investigation Of Photoacoustic Streaming Device

Laser is one of the greatest inventions of the 20 th century.It has the excellent characteristics of pure quality,stable spectrum,collimated direction,and high energy density.Optical fluid control technology has a large number of applications in microfluidic systems,biological and chemical basic research,and medical devices.The use of light to drive fluid has excellent characteristics such as no loss of energy,no contact and no pollution,and easy and precise to control in time and space.Since photons have linear momentum and mechanical kinetic energy,transferring the momentum of the laser to the fluid and controlling the fluid efficiently and accurately has been a research hotspot in recent decades.Most of the current methods use energy conversion methods such as light-heat and light-electricity to indirectly transfer the energy of light to the fluid,which can achieve a movement speed of millimeters per second.In 2017,photoacoustic laser streaming phenomenon was caused by nanosecond pulsed laser incident on gold nanoparticle aqueous solution,and the fluid velocity was increased to the level of 4 cm/s.Subsequent gold ion implantation of the quartz substrate achieved real-time driving of the flow,making it more effective in microfluidic area.However,there are still many unknowns regarding the selection of the best materials for photoacoustic devices and their mechanisms.The effect of ion-implanted metal and substrate materials on the performance of photoacoustic has not been systematically studied.Fabricating photoacoustic high-driving force and long-life devices is still a challenge.This research is based on the research on photoacoustic laser streaming and ion implantation,and further analyzes how to optimize the laser-driven fluid device and its mechanism research from theory and experiment.In this project,corresponding experiments are designed to compare the effects of various parameters on the device from the perspective of duration and flow speed.The effects of different thickness of substrate and different ion implantation concentration on the flow speed of the device were compared,and it was found that the driving force of the flow became stronger with the increase of the implantation concentration.This shows that the driving force of the photoacoustic effect is related to the absorbance;the three types of iron,gold,and tungsten implanted devices are compared by their maximum speed and lifetime under the same conditions.Gold-implanted device is found to have the fastest initial speed,which is related to its relatively high thermal conductivity;but iron and tungsten have longer lifetime,and the holding speed basically does not change during10 to 30 minutes irradiation,which is closely related to its relatively high melting point of the metal.We also analyzed and compared the impact of the type of the substrate on the performance of device,and found that the quartz substrate can give the device the best flow field durability and driving force,because of its low thermal conductivity and less precipitation of particles due to the higher mechanical strength.Finally,this project also designed experiments to explore the impact of different laser power pretreatments on device performance.In addition,the maximum speed under the laser power of 120 m W was measured.Both gold and iron can reach the number level of decimeters per second,which is 3 to 4 times higher than the previously recorded speed under the same power.This provides experimental basis for deeper research of the mechanism of photoacoustic laser streaming and Promote the practical application of devices in the future.