Bioinspired Anisotropic Microstructures Fabricated By Femtosecond Laser And Its Applications Of Droplet Manipulation

Directional droplet/bubble manipulation is widely used in fog collection,chemical microreaction,and biomedical detection.However,the strategies of biomimetic artificial interface superwettable materials and droplet directional manipulation using external field stimulation are both limited by their intrinsic limitations.For example,passive droplet transport based on chemical wetting gradient and structural gradient is limited by velocity and volume range;However,the active droplet manipulation technology based on electric,magnetic,optical and thermal fields is limited by its inherent defects.In this paper,a mechanically tuned droplet manipulation technique based on femtosecond laser fabrication of anisotropic microstructures is proposed,that is,the behavior of droplet and underwater bubble is regulated by mechanical stretching and mechanical vibration.The main research contents include:1.The microgrooves of anisotropic lubrication were prepared by femtosecond laser direct writing technique and lubricant perfusion technique,and in situ reversible tuning of droplet and underwater bubble sliding/pinning was realized by mechanical stretching.The influence of different parameters,such as lubricating oil film thickness,bubble volume and laser power,on droplet/bubble slip behavior was studied.The influence mechanism lies in the decrease of lubricating oil thickness caused by strain,which leads to uneven meniscus of flat and uniform lubricating oil,and further leads to hysteresis of contact Angle and increase of corresponding resistance.Finally,the realtime dynamic manipulation of droplets and underwater bubbles on the surface of microgrooves is demonstrated and its durability and robustness is verified.2.Superhydrophobic slant microwall arrays were prepared by femtosecond laser slant ablation to achieve high performance(multi-mode,large volume ranges and high speed)droplet manipulation by vibration drive.The excellent performance is attributed to the rolling transport mode on the superhydrophobic inclined microwall array.The mechanical mechanism lies in the viscosity resistance caused by the contact area difference between the droplet and the inclined microwall array.Under different excitation amplitudes and frequencies,the optimum groove width corresponds to the optimum droplet transport capacity.Studies the droplet movement along a specific path on an inclined microwall array of a specific shape(annular,curved,and "L").Through the combination of multi-droplet sequential transport and water-based droplet mixing,the water-based droplet mixing microreaction in large volume range is realized,which shows application potential in the field of droplet manipulation.3.The anisotropic lubricating spines array was prepared by femtosecond laser tilting and lubricant infusion,and the high performance directional manipulation of all droplets was realized under horizontal vibration.The principle lies in the competition between the symmetric inertial driving force induced by isotropic vibration and the asymmetric viscous resistance induced by the anisotropic lubrication spines.The influence of machining parameters on structural parameters and the regulation of structural parameters on transportation capacity are studied.The real-time control ability of vibration(frequency and amplitude)on droplet movement is studied to realize high-performance droplet manipulation of droplet rectifier such as super-large volume range(0.05～2000 μL),high-speed velocity(0～60 mm/s),in-tube liquid column transport,programmable sequential transport,bidirectional transport,all-substrate material suitability and durability.The hand-held biomedical detection gun and portable detection box based on droplet rectifier were prepared to lay the foundation for biomedical detection applications(ABO blood group detection and anti-cancer drug screening,etc.).This dissertation combines the anisotropic slippery microstructures prepared by femtosecond laser and mechanical tuning(mechanical drawing and mechanical vibration)strategy,and achieves the control of bubble droplet/underwater directional motion,showing the potential of this method in biomedical detection,chemical reaction,cell engineering,material transport and potential information encryption/decryption.