Lanjiao Liu

Phase difference determination by fringe pattern correlation

This paper presents a method of phase difference determination by fringe pattern correlation in interferometry. In the method, the phase difference between two fringe patterns is determined by fringe pattern correlation and linear interpolation with subpixel accuracy. The experiment shows that this method is useful for the determination of phase difference between two equi-spaced fringe patterns in interferometry, and it has the advantages of high precision of measurement and high resistance to noise.

Phase-shift control in two-beam laser interference lithography

This paper presents a method of phase-shift control in two-beam laser interference lithography. In the method, a PZT actuator is used to push a mirror and introduce phase shifts in a He-Ne laser interference lithography simulation system. When different voltages are applied to the PZT actuator, fringe positions are changed accordingly, and the phase shifts are introduced. The phase shifts can be determined by fringe pattern correlation with subpixel accuracy. This method is useful in two-beam laser interference lithography for the control of phase shifts and fringe positions in interference patterns for multi-exposure patterning applications.

Oblique fringe measurement by pattern correlation

This paper introduces a method for the determination of the slope and period of oblique and equi-spaced fringes by pattern correlation. In the method, two pairs of image patches in two different regions of a fringe pattern are selected for pattern correlation calculations, and the phase shift between the two selected regions of the fringe pattern is obtained from the phase curves computed with the correlation function. The computer simulation and experiment have shown that this method is useful in interferometry and laser interference lithography for determining the slope and period of the oblique and equi-spaced fringe patterns with the advantage of high resistance to noise. It has potential applications for the measurement of the fringe pattern period, fringe angle, phase difference, displacement, and other relevant physical quantities. In practice, it can also be used for the orientation of interference patterns and alignment of laser interference lithography systems.

Measurement of nanoscale surface patterns produced by two-beam laser interference lithography

This paper presents a method for the measurement of nanoscale surface patterns produced by two-beam laser interference lithography (LIL). In the work, the combination of the Hough fitting and the least-squares fitting was first used to fit the edges of the fringe patterns and measure the slopes and periods of them in computer simulation, and then it was also used to inspect the nanoscale surface patterns from a two-beam LIL process. The computer simulation and experimentation results have shown that the method has the advantages of both high resistance to noise and high accuracy of measurement.

Analysis of Colchicine-Induced Effects on Hepatoma and Hepatocyte 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.

Biomechanical measurement and analysis of colchicine-induced effects on cells by nanoindentation using an atomic force microscope

Colchicine is a drug commonly used for the treatment of gout, however, patients may sometimes encounter side-effects induced by taking colchicine, such as nausea, vomiting, diarrhea and kidney failure. In this regard, it is imperative to investigate the mechanism effects of colchicine on biological cells. In this paper, we present a method for the detection of mechanical properties of nephrocytes (VERO cells), hepatocytes (HL-7702 cells) and hepatoma cells (SMCC-7721 cells) in culture by atomic force microscope (AFM) to analyze the 0.1 μg/mL colchicine-induced effects on the nanoscale for two, four and six hours. Compared to the corresponding control cells, the biomechanical properties of the VERO and SMCC-7721 cells changed significantly and the HL-7702 cells did not considerably change after the treatment when considering the same time period. Based on biomechanical property analyses, the colchicine solution made the VERO and SMCC-7721 cells harder. We conclude that it is possible to reduce the division rate of the VERO cells and inhibit the metastasis of the SMCC-7721 cells. The method described here can be applied to study biomechanics of many other types of cells with different drugs. Therefore, this work provides an accurate and rapid method for drug screening and mechanical analysis of cells in medical research.

Axisymmetric Contact Problem for a Flattened Cell: Contributions of Substrate Effect and Cell Thickness to the Determination of Viscoelastic Properties by Using AFM Indentation

Nanoindentation technology has proven to be an effective method to investigate the viscoelastic properties of biological cells. The experimental data obtained by nanoindentation are frequently interpreted by Hertz contact model. However, in order to validate Hertz contact model, some studies assume that cells have infinite thickness which does not necessarily represent the real situation. In this study, a rigorous contact model based upon linear elasticity is developed for the interpretation of indentation tests of flattened cells. The cell, normally bonded to the Petri dish, is initially treated as an elastic layer of finite thickness perfectly fixed to a rigid substrate. The theory of linear elasticity is utilized to solve this contact issue and then the solutions are extended to viscoelastic situation which is regarded as a good indicator for mechanical properties of biological cells. To test the present model, AFM-based creep test has been conducted on living human hepatocellular carcinoma cell (SMMC-7721 cell) and its fullerenol-treated counterpart. The results indicate that the present model could not only describe very well the creep behavior of SMMC-7721 cells, but also curb overestimation of the mechanical properties due to substrate effect.

Nanomanipulation of single nanowires on structured surfaces fabricated by laser interference lithography

Nanomanipulation is an important technology to fabricate and assemble nanostructures, especially for the asymmetrical structures. This paper presents a method of manipulation of single nanowires on structured surfaces by nano grippers in a scanning electron microscope (SEM). In the method, the structured surfaces of substrate were fabricated by two-beam laser interference lithography. Single nanowires were manipulated on the structured surfaces by nano grippers in the SEM. The method uses a pattern to solve the problem that a single nanowire is too tiny to be picked up and manipulated with nano grippers.

Fabrication of the InP nanopillars

This paper presents a way to fabricate nanopillars of InP, which is obtained based on the nanosphere mask by electrochemical etching. The nanopillars are cylinder-shaped, and the smallest feature size can be ∼5nm. The results have shown that the formation of the nanopillars is devoted to the areas of the tangency between the nanospheres and the wafer. The blue shift peak of photoluminescence spectra was observed in room temperature, and it was approximately 21meV and attributed to the quantum confinement effect.