Jian-Nan Wang

Jilin University, Jilin, Jilin Sheng, China

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Publications (9)41.69 Total impact

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    ABSTRACT: TWo-beam-laser interference was used for the simultaneous reduction, patterning and nanostructuring of graphene oxide on flexible polyethylene terephthalate substrates for the production of a high performance humidity sensing device. Hierarchical graphene nanostructures were formed after laser interference treatment of graphene oxide, which holds great promise for gaseous molecular adsorption, and thereby significantly increases their sensing performance. By tuning the laser power, the content of oxygen functional groups, could be changed within a certain range, which contributes not only controllable conductivity but also tunable response/recovery time of the humidity sensor due to the interaction between water molecules and oxygen functional groups on the graphene oxide sheets. The laser interference processing of graphene oxide films is a mask-free, surfactant-free and large-area approach to the production of hierarchical graphene micro-nanostructures, and thus shows great potential for fabrication of future graphene-based microdevices. (C) 2011 Elsevier Ltd. All rights reserved.
    Carbon. 04/2012; 50(4):1667-1673.
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    Chemistry - An Asian Journal 02/2012; 7(2):301-4. · 4.57 Impact Factor
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    ABSTRACT: Composition modification and surface microstructures have been widely utilized in interface science to improve the surface performance. In this paper, we observed a significant improvement of oil contact angle (CA) from 66 ± 2° to 120 ± 4° by introducing a radical silanol group on a flat PDMS surface through oxygen plasma pretreatment. By combining surface microstructures and plasma modification, we produced three kinds of superoleophobic surfaces: 20 μm pitch micropillar arrays, 2.5 μm pitch micropillar arrays and gecko foot-like hierarchical microstructures. Among them, the hierarchical surface with high surface roughness showed extreme underwater superoleophobicity, which featured ultrahigh CA (175 ± 3°) and ultrasmall sliding angle (<1°). Quantitative measurements demonstrated that these superoleophobic surfaces exhibited distinct adhesive behaviors, by which they were interpreted as Wenzel's, Cassie's and the Lotus state, respectively. A microfluidic channel with superoleophobic microstructures was further created by novel curve-assisted imprint lithography, and the characterization based on anti-oil contamination applications was carried out and discussed. We believe that the superoleophobic surfaces will power broad applications in oil microdroplet transportation, anti-oil channels and droplet microfluidic systems.
    Lab on a Chip 09/2011; 11(22):3873-9. · 5.70 Impact Factor
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    ABSTRACT: Reported here is a facile synthesis of nanoporous polymer chalk for painting superhydrophobic surfaces. Taking this nanoporous polymer as a media, superhydrophobicity is rapidly imparted onto three typical kinds of substrates, including paper, transparent polydimethylsiloxane (PDMS), and finger skin. Quantitative characterization showed that the adhesion between the water droplet and polymer-coated substrates decreased significantly compared to that on the original surface, further indicating the effective wetting mode transformation. The nanoporous polymer coating would open a new door for facile, rapid, safe, and larger scale fabrication of superhydrophobic surfaces on general substrates.
    Langmuir 08/2011; 27(20):12585-90. · 4.19 Impact Factor
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    ABSTRACT: Rice leaves with anisotropic sliding properties have the ability to directionally control the movement of water microdroplets. However, the realization of artificial anisotropic sliding biosurfaces has remained challenging. It is found, by a systematic investigation, that the height of 200-mu m-width groove arrays on rice leaves reaches up to 45 mu m, far greater than the smaller microgrooves that are widely adopted for the study of anisotropic wetting. A new model based on three-level microstructures (macro/micro/nano) is developed to interpret the anisotropic sliding behavior. Moreover, artificial rice leaves with different macrogrooves are demonstrated by combining micro/nanostructures and macrogrooves, which are prepared by photolithography, PDMS imprinting, and micro/nanostructure coating. Sliding-angle measurement further prove that the third-level macrogroove arrays are the determining factor for anisotropic sliding. Finally, a new testing method, curvature-assisted droplet oscillation (CADO), is developed to quantitatively reveal the anisotropic dynamic behavior of biomimetic rice-leaf-like surfaces.
    Advanced Functional Materials 05/2011; 21(15):2927 - 2932. · 9.77 Impact Factor
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    ABSTRACT: In this letter, we report a kind of smart surfaces with reversible switching between isotropy and anisotropic wetting, which was realized by one-direction curvature tuning on flexible superhydrophobic surfaces. Along the curvature change, the wettability of this flexible film was changed from isotropic state (150°/150°) into anisotropic state confirmed by its anisotropic contact angles (150°/160°) and sliding properties (30°/65°). Further investigation revealed that the surface wettability was changed from composited pinned state into transitional state. This was attributed to the increase in roughness factor and the decrease in the contact area between the water droplet and the pillar array. At last, we demonstrate that the wetting states between isotropy and anisotropy on this flexible superhydrophobic film could be reversibly switched by curvature for many times (>10).
    Applied Physics Letters 02/2011; 98(8):081902-081902-3. · 3.79 Impact Factor
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    ABSTRACT: In this paper, one simple method to control two-direction anisotropic wetting by regular micropearl arrays was demonstrated. Various micropearl arrays with large area were rapidly fabricated by a kind of improved laser interference lithography. Specially, we found that the parallel contact angle (CA) theta(2) decreased from 93 degrees to 67 degrees as the intensity ratio of four laser beams increased from 2:1 to 30:1, while the perpendicular CA theta(1) determined by the thickness of the resin remained constant. This was interpreted as the decrease of height variations Delta h from 1100 to 200 nm along the parallel direction caused by the increase of the intensity ratio. According to this rule, both theta(1) and theta(2) could be simultaneously controlled by adjusting the height variation Delta h and the resin thickness. Moreover, by combining appropriate design and low surface energy modification, a natural anisotropic rice leaf exhibiting CAs of 146 degrees +/- 2 degrees/153 degrees +/- 3 degrees could be mimicked by our anisotropic biosurface with the CAs 145 degrees +/- 1 degrees/150 degrees +/- 2 degrees. We believe that these controlled anisotropic biosurfaces will be helpful for designing smart, fluid-controllable interfaces that may be applied in novel microfluidic devices, evaporation-driven micro/nanostructures, and liquid microdroplet directional transfer.
    Langmuir 07/2010; 26(14):12012-6. · 4.19 Impact Factor
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    ABSTRACT: The study of anisotropic wetting has become one of the most important research areas in biomimicry. However, realization of controlled anisotropic surfaces remains challenging. Here we investigated anisotropic wetting on grooves with different linewidth, period, and height fabricated by laser interference lithography and found that the anisotropy strongly depended on the height. The anisotropy significantly increased from 9° to 48° when the height was changed from 100 nm to 1.3 μ m . This was interpreted by a thermodynamic model as a consequence of the increase of free energy barriers versus the height increase. According to the relationship, controlled anisotropic surfaces were rapidly realized by adjusting the grooves’ height that was simply accomplished by changing the resin thickness. Finally, the perpendicular contact angle was further enhanced to 131°±2° by surface modification, which was very close to 135°±3° of a common grass leaf.
    Applied Physics Letters 03/2010; · 3.79 Impact Factor
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    ABSTRACT: Microfluidic researches are now resorting to advanced micro-nanoprocessing technologies for production of more functional "lab-on-a-chip" systems. However, two-photon polymerization (TPP), a powerful designable micro-nanofabrication approach, has not been put to use on the exciting field, largely due to the difficulties in forming buried channels. Here, we solve the problem by TPP prototyping of nanoshells, for which the usage of the negative tone resin SU-8 is found critical. The fabrication efficiency improved by orders of magnitude, together with the prospect of integration of movable micro-mechanical and optical components into the chip would make TPP a promising enabling tool for the micro-analytical systems. Finally, a 25 microm length functional microvalve in a microfluidic channel was rapidly realized and its "ON" and "OFF" states were tested.
    Lab on a Chip 09/2009; 9(16):2391-4. · 5.70 Impact Factor