Bionic Functional Structure By Femtosecond Laser Micro/Nanofabrication Technologies

Biotic community in nature has experienced a long evolution natural selection and survival of the fittest, and formed their own unique function structure and behavior, to maintain the harmony of man and nature. In natural imitation, myriad creatures provide human with inspiration and wisdom.In this paper, we developed a relational model about the relationship between the laser parameters and the induced micro/nanostructures by combining the femtosecond laser micro/nano machining technology and the bionic design principles. We also studied the formation mechanism of the structural colors, hydrophobic surfaces and underwater superoleophobic surfaces. In addition, we discussed the controllabilities of the laser induced micro/nanostructures, and verified the functions experimentally. The details were as following:(1) Proceed from the formation mechanism of the structural colors in nature, we have mastered the preparation of colors by studying how the laser machining parameters impact on the induced micro/nanostructures. By adopting different speeds of scanning femtosecond laser, several kinds of structural colors, such as golden, white, gray, and black, were produced on the aluminum surfaces. Considering the laser induced periodic surface structures (LIPSSs) as a kind of grating structures, we not only discussed the combined influence of incident light angle and the ripples orientation on the diversity of structural colors, but also proposed the possibility of producing multi-patterns constituted by ripples with different orientations, and realized the diverse and exclusive display. An innovative method was proposed to produce three-dimensional effect patterns on metal surface by translating each layer in one direction, In addition, a systematic study was performed on the dependence of structural colors on the laser wavelengths. Finally, porous protrusions and stagger stripes were produced by ethanol-assisted femtosecond laser irradiation to induce various uniform structural colors on nickel surfaces.(2) We developed a facile approach to prepare large-area functional polymer surfaces duplicated from the metal. The aluminum is firstly scanned by femtosecond laser beam with different pulse overlaps to form hierarchical structures. Then the aluminum pieces act as template masters and the hierarchical structures are subsequently transferred onto polydimethyl-siloxane (PDMS) surfaces. It is found that the polymer replicas are endowed with tunable wetting properties. The reusability of metal master and easiness of soft lithography make it to be a very simple, fast and cost-efficient way for mass production of functional polymeric surfaces.(3) Metallic micro/nanostructures with controllable2D-3D geometries have been attracting great attention due to their many promising applications ranging from plasmonics, electronics, and bioscience to chemistry. However, the present method of prepared these micro/nanostructures have disadvantages, such as complicated processing, time-consuming, high cost, and small area and so on. We developed a facile and rapid method to fabricate large-area3-dimensional porous metal micro/nanocages arrays with0.8um sizes by one-step ethanol-assisted femtosecond laser irradiation on nickel surfaces. The underlying formation mechanism was investigated by a series of fs laser irradiation under exposure time from5to30ms. By controlling the laser energy, micro/nanocage arrays with different size from0.8to2[im were obtained. Furthermore, these porous3-D controllable cage-like micro/nanostructures exhibit not only enhanced antireflection from80%to7%but also hydrophobicity with contact angle from98°to142°without surface modification.(4) The underwater superoleophobic of the fish scales can make the oil droplet roll form the fish body losslessly, which maintains fish live freely in pollutional water. We produced self-organized conical microstructures covered by nanovillus arrays on nickel surface by sucrose solution-assisted femtosecond laser irradiation. In addition, the size of the conical microstructures can be controlled by different laser pulse energy and mass ratio of sucrose and water in the solution. It is found that these hierarchical micro/nanostructures surface are superhydrophilic in air, and superoleophobic in water. Our study shows that the contact angle of water and oil in air, oil underwater, and sliding angle of oil underwater are tunable by the different size of conical microstructures. The experimental results show that the structured nickel can be used in liquid storage, fluid controlling, mixing and transfer. This method features simplicity, ease of large-area, good controllability, non-pollution, and low cost, will find great potential applications in microfluidics, microsensor, and biomedicine.