Micro and nano dual-scale structures fabricated by amplitude modulation in multi-beam laser interference lithography

© 2017 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reservedIn this work, an effective method was presented to obtain a specific micro and nano dual-structures by amplitude modulation in multi-beam laser interference lithography (LIL). Moiré effect was applied to generate the amplitude modulation. The specific intensity modulation patterns can be obtained by the control of the parameter settings of incident laser beams. Both the incident angle and azimuth angle asymmetric configurations can cause the amplitude modulation in the interference optic field and the modulation period is determined by the angle offset. A four-beam LIL system was set up to fabricate patterns on photoresist and verify the method. The experimental results are in good agreement with the theoretical analysis

Fabrication of periodically micropatterned magnetite nanoparticles by laser-interference-controlled electrodeposition

This paper introduces a laser-interference-controlled electrochemical deposition method for direct fabrication of periodically micropatterned magnetite (Fe3O4) nanoparticles (NPs). In this work, Fe3O4 NPs were controllably synthesized on the areas where the photoconductive electrode was exposed to the periodically patterned interferometric laser irradiation during the electrodeposition. Thus, the micropattern of Fe3O4 NPs was controlled by interferometric laser pattern, and the crystallization of the particles was controlled by laser interference intensity and electrochemical deposition conditions. The bottom-up electrochemical approach was combined with a top-down laser interference methodology. This maskless method allows for in situ fabrication of periodically patterned magnetite NPs on the microscale by electrodeposition under room temperature and atmospheric pressure conditions. In the experiment, Fe3O4 NPs with the mean grain size below 100 nm in the pattern of 5-lm line array were achieved within the deposition time of 100 s. The experiment results have shown that the proposed method is a one-step approach in fabricating large areas of periodically micropatterned magnetite NPs

Fast Fourier transport analysis of surface structures fabricated by laser interference lithography

This paper presents an FFT (fast Fourier transform) analytical method for the study of surface structures fabricated by laser interference lithography (LIL). In the work, the FFT analytical method combined with Gaussian fitting is used to determine the periods and pattern distributions of surface structures from frequency spectra. For LIL, the processing parameters of incident and azimuth angles can be obtained corresponding to the period and pattern distribution. This work facilitates the detection of micro- and nano-structures, the analysis of pattern distribution in engineering, and the processing error analysis of LIL

Templated assembly of micropatterned Au-Ni nanoparticles on laser interference-structured surfaces by thermal dewetting

This paper introduces a laser-interference-controlled electrochemical deposition method for direct fabrication of periodically micropatterned magnetite (Fe3O4) nanoparticles (NPs). In this work, Fe3O4 NPs were controllably synthesized on the areas where the photoconductive electrode was exposed to the periodically patterned interferometric laser irradiation during the electrodeposition. Thus, the micropattern of Fe3O4 NPs was controlled by interferometric laser pattern, and the crystallization of the particles was controlled by laser interference intensity and electrochemical deposition conditions. The bottom-up electro- chemical approach was combined with a top-down laser interference method- ology. This maskless method allows for in situ fabrication of periodically patterned magnetite NPs on the microscale by electrodeposition under room temperature and atmospheric pressure conditions. In the experiment, Fe3O4 NPs with the mean grain size below 100 nm in the pattern of 5-lm line array were achieved within the deposition time of 100 s. The experiment results have shown that the proposed method is a one-step approach in fabricating large areas of periodically micropatterned magnetite NPs.

Analysis of colchicine-induced effects on hepatoma and hepatpcyte cells by atomic force microscopy

Biomechanical properties of cells are altered by many diseases. Cancer cell metastasis is related to the properties such as the cell stiffness that influences cell proliferation, differentiation and migration. In this paper, we used an atomic force microscope to analyze the colchicine-induced effects on the mechanical properties of hepatocyte (HL-7702 cells) and hepatoma cells (SMCC-7721 cells) in culture at the nanoscale. The cells were exposed to a solution with a normal dose of colchicine for two, four and six hours. Surface topographic images showed that colchicine decreased the stability of the cytoskeleton. After the same six-hour treatment in a solution with a normal dose of colchicine, the biomechanical properties of HL-7702 cells were almost unchanged. However, the stiffness and the adhesion force of the SMCC-7721 cells were clearly increased (more than twofold of the normal values), especially after four hours. The deformability of SMCC-7721 cancer cells was significantly decreased within the six-hour treatment in the solution with a normal dose of colchicine. Analysis of the biomechanical properties of post-treatment hepatoma cells provided a complementary explanation for the mechanism of action of colchicine on cells at the nanoscale. This method is expected to allow the monitoring of potential metastatic cancer cell changes, thus preventing the emergence and the transmission of disease, and improving the diagnosis of cancer

Fabrication of cross-scale structures by Moiré effect in laser interference lithography

This paper presents a method for the fabrication of cross-scale structures using the controllable Moiré effect to break through the scale barriers caused by the spatial distribution in a laser interference lithography (LIL) system. The formation principle of macroscopic Moiré gratings in the LIL system was analyzed as partial wavefront interference introduced by optical components. In this work, an additional lens was used in the improved two-beam LIL system to precisely control the size of Moiré gratings, combined with the intrinsic period in the LIL system to form a cross-scale distribution of light intensity. This method provides a way for the fabrication of cross-scale surface structures by single exposure. Through the double-exposure technology, the fabrication of isotropic and anisotropic structures can be achieved flexibly for different applications, such as photonic crystals, self-cleaning surfaces, structural color elements and anti-counterfeiting labels

Improved DNA straightening and attachment via optimal Mg2+ ionic bonding under electric field for AFM imaging in liquid phase

In this research, a novel method is proposed to improve DNA straightening under an applied electric field to facilitate imaging in a liquid phase by modifying the substrate with varying Mg2+ ion concentrations. A two-dimensional network of DNA structures was successfully stretched on Mg2+-modified mica substrates under a DC electric field (1 V, 1 A) and imaged in gaseous and aqueous phases by atomic force microscopy. The results revealed that an optimum concentration of Mg2+ ion (4.17 μmol/ml) allowed DNA straightening under an electric field, thus facilitating its imaging in the liquid phase. Furthermore, DNA adhesion under different concentrations of Mg2+ was measured and a maximum adhesion force of 76.19 pN was achieved. This vital work has great potential in gene knockout and targeted gene editing

Vacuum conditions for tunable wettability transition on laser ablated Ti-6Al-4V alloy surfaces

This work investigates the mechanism of the controllable wettability transition on laser ablated Ti-6Al-4V alloy surfaces with the vacuum treatment. The effects of surface morphologies, vacuum conditions and joint mechanisms are discussed. To achieve stable and controllable wettability transitions, the laser ablated Ti-6Al-4V alloy surfaces were placed in a low vacuum environment to adsorb non-polar organic molecules. The sample appeared an unstable wettability transition, which manifested itself as a change in the apparent contact angle (ACA) with time. High vacuum conditions can accelerate the assembly of organic molecules on the sample surface and achieve a stable wettability transition. Furthermore, by varying the surface morphologies of laser ablated Ti-6Al-4V alloy and the adsorption time of organic molecules, stable and controllable wettability transitions can be achieved at high vacuum conditions

Nanosecond Laser-Induced Underwater Superoleophobic and Underoil Superhydrophobic Mesh for Oil/Water Separation

Materials with special wettability have drawn considerable attention especially in the practical application for the separation and recovery of the oily wastewater, whereas there still remain challenges of the high-cost materials, significant time, and complicated production equipment. Here, a simple method to fabricate the underwater superoleophobic and underoil superhydrophobic brass mesh via the nanosecond laser ablation is reported for the first time, which provided the micro-/nanoscale hierarchical structures. This mesh is superhydrophilic and superoleophilic in air but superoleophobic under water and superhydrophobic under oil. On the basis of the special wettability of the as-fabricated mesh, we demonstrate a proof of the light or heavy oil/water separation, and the excellent separation efficiencies (>96%) and the superior water/oil breakthrough pressure coupled with the high water/oil flux are achieved. Moreover, the nanosecond laser technique is simple and economical, and it is advisable for the large-area and mass fabrication of the underwater superoleophobic and underoil superhydrophobic mesh in the large-scale oil/water separation