Combining Laser Processing With Stimuli Responsive Materials To Fabricate Bioinspired Functional Microstructures And Their Applications

After long-term survival competition and natural selection,animals and plants have evolved various unique functions that adapt to the environment.With the development of modern microscopic imaging technology,it is found that these animals and plants have some unique surface micro-nano structures,combined with the chemical characteristics of the surface,thereby generating unique functions to help organisms survive the cruel natural selection.Based on the concept of learning from nature for serving human life and the development of science and technology,bionics was born.In the preparation of bionic functional surface structures,various micro-nano processing methods have been successfully used.However,with the increasing complexity of the structure of bionic objects,the traditional planar micro-nano machining technology has weak ability in forming a complex structure,and 3D printing technology has the limitations of narrow selection of materials and difficulty in balancing efficiency and accuracy,thus,it is more difficult to meet the demand for manufacturing of complex three-dimensional functional devices with high efficiency and resolution.This situation has driven people to explore 3D micro-nano machining methods.Femtosecond laser micro-nano processing technology,as an emerging processing method,has the advantages of high processing accuracy,wide processing material range,no need for masks,and low environmental requirements.At the same time,the technology can also achieve surface chemical modification.In this paper,based on femtosecond laser micro-nano processing technology,combined with the deformability of stimuli responsive materials,each takes advantages,we propose a low-cost,scalable three-dimensional micro-nano structure composite processing technology,and show the application in underwater air layer retention,information encryption/decryption,and micro-object capature.Focusing on the polymer self-growing technology by combining with femtosecond laser and deformability of stimuli responsive materials,the content of this article mainly includes:1.Introducing the prototype of wettability functional surface in nature,wettability theory,current wettability surface preparation methods and deficiencies,and the progress of microfabrication technology based on stimuli response materials.Last,the research significance and content of the subject are proposed.2.Introducing the femtosecond laser micro-nano processing platform,and then a method using this platform to fabricate a three-dimensional pillar structure on the surface of the biaxially stretched silicone membrane is introduced,thus the principle of polymer self-growth is preliminary explored.Subsequently,through designing the processing sequence,the bending direction of the micro-pillar can be controlled.Moreover,after the micropillar structure is fabricated on the surface of the hydrophobic silicone membrane,the bionic manufacturing of the lotus effect is realized.On the surface of the hydrophilic modified silicone membrane,the micropillars are fabricated to realize the hydrophilic-hydrophobic switchable function.3.The femtosecond laser is used to achieve controlled polymer self-growth and the fabricated structure is in-situ tuned on the surface of the heat-responsive shrinkable polystyrene film,thus the polymer self-growth method is further developed.The principle of polymer self-growing and bending is explored in detail.Taking full advantage of the high flexibility of the femtosecond laser processing technology,a variety of cross-section straight micropillars and diverse surface assembly structures have been prepared.Subsequently,the application in surface micro-object capture/release,information encryption/decryption and surface wettability control are demonstrated.4.The polymer self-growth method is further developed by using a femtosecond laser to cut the heat-shrinkable film and then externally heating the microcube with the top constrained by the tape to achieve self-growth and self-branch of the polymer structure.After being modified with low surface energy,the branch structure is used to trap the hydrophilic SiO2 microspheres.Thereby realizing the preparation of the Salvinia inspired artificial structure which shown eggbeater shape with the hydrophilic top.Subsequently,the application of the non-loss transport of droplets is demonstrated with the three-level branch structure.5.Various structures prepared by the self-growth and self-branch method are characterized for the ability to maintain the underwater air layer The changes of the surface air layer and the air-water interface are characterized under the conditions of negative pressure and positive pressure,respectively.The results confirmed that the microspheres-branches composite structure has the best air layer retention ability.The pinning effect of hydrophilic microspheres is verified when the gas-liquid interface is away from the top of the structure.It is found that when the gas-liquid interface is close to the top of the structure,the hydrophilic microspheres will adsorb the interface like a magnet which is helpful to recover the interface.