Article

A simple strategy to realize biomimetic surfaces with controlled anisotropic wetting

State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, People's Republic of China
Applied Physics Letters (Impact Factor: 3.3). 03/2010; 96(5):053704 - 053704-3. DOI: 10.1063/1.3297881
Source: IEEE Xplore

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.

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Available from: Hong-Bo Sun, Oct 31, 2014
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    • "But, both theoretically and experimentally, the beam incidence conditions play a critical role in the determination of period and contrast in the formation of interference patterns. It is known that the period of interference can be controlled by changing the incident angles of beams or the radiation wavelength [13]. For practical applications, the wavelength is first selected so that the period depends on the incident angles. "

    Full-text · Dataset · Oct 2015
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    • "But, both theoretically and experimentally, the beam incidence conditions play a critical role in the determination of period and contrast in the formation of interference patterns. It is known that the period of interference can be controlled by changing the incident angles of beams or the radiation wavelength [13]. For practical applications, the wavelength is first selected so that the period depends on the incident angles. "
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    ABSTRACT: Beam incidence conditions in the formation of two-, three- and four-beam laser interference patterns are presented and studied in this paper. In a laser interference lithography (LIL) process, it is of importance to determine and control beam incidence conditions based on the analysis of laser interference patterns for system calibration as any slight change of incident angles or intensities of beams will introduce significant variations of periods and contrasts of interference patterns. In this work, interference patterns were captured by a He–Ne laser interference system under different incidence conditions, the pattern period measurement was achieved by cross-correlation with, and the pattern contrast was calculated by image processing. Subsequently, the incident angles and intensities of beams were determined based on the analysis of spatial distributions of interfering beams. As a consequence, the relationship between the beam incidence conditions and interference patterns is revealed. The proposed method is useful for the calibration of LIL processes and for reverse engineering applications.
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    • "Therefore, the static contact angle differs along the TPCL. Some researchers addressed the wetting characteristic as " anisotropic wetting " , as opposed to the isotropic wetting [10] [11] [12] [13] [14]. Due to the capacity of restricting liquids to flow toward desired direction, the anisotropic wetting has attracted remarkable attentions on microfluidic devices [15] [16] [17] [18]. "
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    ABSTRACT: Anisotropic wetting of machined surfaces is widely applied in industries which can be greatly affected by roughness and solid's chemical properties. However, there has not been much work on it. A free-energy thermodynamic model is presented by analyzing geometry morphology of machined surfaces (2-D model surfaces), which demonstrates the influence of roughness on anisotropic wetting. It can be concluded that the energy barrier is one of the main reasons for the anisotropic wetting existing in the direction perpendicular to the lay. In addition, experiments in investigating anisotropic wetting, which was characterized by the static contact angle and droplet's distortion, were performed on machined surfaces with different roughness on hydrophilic and hydrophobic materials. The droplet's anisotropy found on machined surfaces increased with mean slope of roughness profile Kr. It indicates that roughness on anisotropic wetting on hydrophilic materials has a stronger effect than that on hydrophobic materials. Furthermore, the contact angles predicted by the model are basically consistent with the experimentally ones.
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