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Femtosecond laser rapid fabrication of large-area rose-like micropatterns on freestanding flexible graphene films.

Shi X, Li X, Jiang L, Qu L, Zhao Y, Ran P, Wang Q, Cao Q, Ma T, Lu Y - Sci Rep (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, PR China.

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.

No MeSH data available.


C1s XPS spectra of the pristine and patterned graphene films.(a) Pristine graphene film without surface patterning. (b,c) Patterned graphene films with increasing flower densities. The densities in (b,c) are equal to those in Fig. 5c and Fig. 5d, respectively.
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f6: C1s XPS spectra of the pristine and patterned graphene films.(a) Pristine graphene film without surface patterning. (b,c) Patterned graphene films with increasing flower densities. The densities in (b,c) are equal to those in Fig. 5c and Fig. 5d, respectively.

Mentions: To further substantiate the effects of laser patterning on the wetting properties of graphene films, XPS and AFM were used to investigate the chemical composition and the surface geometry, respectively. The oxygen content of the pristine surface and patterned graphene films with flower densities equal to that in Fig. 5c and d were measured by C1s XPS. As shown in Fig. 6, the binding energy of the C-C is assigned at 284.6 eV and chemical shifts of + 1.5 and + 2.5 are assigned for the C-OH and C = O functional groups, respectively28. The XPS results show that the oxygen content of the pristine graphene film is 29.03%, while the patterned surfaces with microflowers just next to each other (Fig. 5c) and partially overlapped (Fig. 5d) are 12.39% and 6.76%, respectively. The XPS results indicate that the oxygen groups have been successfully reduced by fs laser ablation and the oxygen content decreases with the increase of the flower density. Hence, a further removal of hydrophilic oxygen groups by fs laser ablation may play an important role in the enhanced hydrophobicity of the patterned graphene films. Besides, the surface roughness (Ra) of graphene films with different flower densities was also investigated by AFM as shown in Fig. 5e. Generally, the CA changes according to the surface roughness. Because of the turnup graphene flakes, the edges of the exfoliated graphene flakes were exposed to the surface. On the surfaces with plenty of graphene edges, a mix of solid/liquid and liquid/air interfaces can be created compared to the solid/liquid interface on the plain samples, resulting in an increasing water contact angle26. However, further increase of the flower density (i.e. D > 1.49) leads to a slight decrease of the contact angle. According to the scanning technique, a larger flower density means more laser pulses applied on unit area. The additional pulses applied on the preexisting microflowers can result in an increase of the density of graphene flakes but a decrease in volume of cavities between the turnup nanoflakes, which may be responsible for the slight decrease in the contact angle at a larger flower density.


Femtosecond laser rapid fabrication of large-area rose-like micropatterns on freestanding flexible graphene films.

Shi X, Li X, Jiang L, Qu L, Zhao Y, Ran P, Wang Q, Cao Q, Ma T, Lu Y - Sci Rep (2015)

C1s XPS spectra of the pristine and patterned graphene films.(a) Pristine graphene film without surface patterning. (b,c) Patterned graphene films with increasing flower densities. The densities in (b,c) are equal to those in Fig. 5c and Fig. 5d, respectively.
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Related In: Results  -  Collection

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f6: C1s XPS spectra of the pristine and patterned graphene films.(a) Pristine graphene film without surface patterning. (b,c) Patterned graphene films with increasing flower densities. The densities in (b,c) are equal to those in Fig. 5c and Fig. 5d, respectively.
Mentions: To further substantiate the effects of laser patterning on the wetting properties of graphene films, XPS and AFM were used to investigate the chemical composition and the surface geometry, respectively. The oxygen content of the pristine surface and patterned graphene films with flower densities equal to that in Fig. 5c and d were measured by C1s XPS. As shown in Fig. 6, the binding energy of the C-C is assigned at 284.6 eV and chemical shifts of + 1.5 and + 2.5 are assigned for the C-OH and C = O functional groups, respectively28. The XPS results show that the oxygen content of the pristine graphene film is 29.03%, while the patterned surfaces with microflowers just next to each other (Fig. 5c) and partially overlapped (Fig. 5d) are 12.39% and 6.76%, respectively. The XPS results indicate that the oxygen groups have been successfully reduced by fs laser ablation and the oxygen content decreases with the increase of the flower density. Hence, a further removal of hydrophilic oxygen groups by fs laser ablation may play an important role in the enhanced hydrophobicity of the patterned graphene films. Besides, the surface roughness (Ra) of graphene films with different flower densities was also investigated by AFM as shown in Fig. 5e. Generally, the CA changes according to the surface roughness. Because of the turnup graphene flakes, the edges of the exfoliated graphene flakes were exposed to the surface. On the surfaces with plenty of graphene edges, a mix of solid/liquid and liquid/air interfaces can be created compared to the solid/liquid interface on the plain samples, resulting in an increasing water contact angle26. However, further increase of the flower density (i.e. D > 1.49) leads to a slight decrease of the contact angle. According to the scanning technique, a larger flower density means more laser pulses applied on unit area. The additional pulses applied on the preexisting microflowers can result in an increase of the density of graphene flakes but a decrease in volume of cavities between the turnup nanoflakes, which may be responsible for the slight decrease in the contact angle at a larger flower density.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, PR China.

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.

No MeSH data available.