Abstract
We developed a simple, scalable and high-throughput method for fabrication of large-area three-dimensional rose-like microflowers with controlled size, shape and density on graphene films by femtosecond laser micromachining. The novel biomimetic microflower that composed of numerous turnup graphene nanoflakes can be fabricated by only a single femtosecond laser pulse, which is efficient enough for large-area patterning. The graphene films were composed of layer-by-layer graphene nanosheets separated by nanogaps (~10–50 nm), and graphene monolayers with an interlayer spacing of ~0.37 nm constituted each of the graphene nanosheets. This unique hierarchical layering structure of graphene films provides great possibilities for generation of tensile stress during femtosecond laser ablation to roll up the nanoflakes, which contributes to the formation of microflowers. By a simple scanning technique, patterned surfaces with controllable densities of flower patterns were obtained, which can exhibit adhesive superhydrophobicity. More importantly, this technique enables fabrication of the large-area patterned surfaces at centimeter scales in a simple and efficient way. This study not only presents new insights of ultrafast laser processing of novel graphene-based materials but also shows great promise of designing new materials combined with ultrafast laser surface patterning for future applications in functional coatings, sensors, actuators and microfluidics.
Highlights
Patterning and etching procedure in fabrication of the specific substrate
It is worth noting that the microflowers can be obtained on graphene films that have unique hierarchical layering structures, while they cannot be fabricated on highly oriented pyrolytic graphite (HOPG) films with a uniform interlayer spacing
The microflowers consist of graphene nanoflakes that were exfoliated from the surface by fs laser pulse, which are geometrically similar to the fragmentation of thin spalls induced by tensile stress[31]
Summary
Patterning and etching procedure in fabrication of the specific substrate. How to high-throughput fabrication of 3D hierarchical structures on graphene in a controlled manner still remains as open questions. Many lasers can be used as light sources in direct writing process, but not all of them are capable of making three-dimensional patterns on graphene films with high-throughput in large-scale. The femtosecond laser (fs) has been proved to have unique capabilities for scalable, high-throughput, controllable, and three-dimensional processing[18,19,20]. The 3D rose-like structure can be obtained by only one laser pulse, which offers great potential for the high-throughput large-scale manufacturing. Our approach shows potential application in fabrication of centimeter-scale 3D micro/nanostructures in a controllable and highly-efficient manner, which is distinct from earlier reports in that the graphene film itself served as an important precursor for the formation of graphene microflowers when it was processed with fs laser pulses
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