Zhengxun Song

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.

Fabrication of Pt nanowires with a diffraction-unlimited feature size by high-threshold lithography

Although the nanoscale world can already be observed at a diffraction-unlimited resolution using far-field optical microscopy, to make the step from microscopy to lithography still requires a suitable photoresist material system. In this letter, we consider the threshold to be a region with a width characterized by the extreme feature size obtained using a Gaussian beam spot. By narrowing such a region through improvement of the threshold sensitization to intensity in a high-threshold material system, the minimal feature size becomes smaller. By using platinum as the negative photoresist, we demonstrate that high-threshold lithography can be used to fabricate nanowire arrays with a scalable resolution along the axial direction of the linewidth from the micro- to the nanoscale using a nanosecond-pulsed laser source with a wavelength λ0 = 1064 nm. The minimal feature size is only several nanometers (sub λ0/100). Compared with conventional polymer resist lithography, the advantages of high-threshold lithogra...

Mechanical properties study of SW480 cells based on AFM.

Since the invention of the atomic force microscope (AFM), it has been widely applied in biomedicine. One of the most important applications is used as an indenter tool to do the indentation experiment in order to get the mechanical properties of cells. In this paper, SW480 cells were used as the test subjects. Through the analysis of the contact and indentation, Youngs modulus (E), which is an important parameter of cancer cells, has been estimated. Experimental results show that different mechanical models should be chosen to calculate the E in different indentation depths. Here, the E of SW480 cells was (2.5 ± 0.8) KPa at the indentation depth of 99 nm.

Five-beam Interference Pattern Model for laser interference lithography

Laser interference lithography (LIL) is an established fabrication technology for micro and nano scale structuring of periodic and quasi-periodic surface patterns. This paper presents a Five-beam Interference Pattern Model for laser interference lithography. It can be programmed to obtain images of interference results showing interference intensity distributions. The majority of 2–5 beam interference patterns can be simulated by this model with every variable in an LIL system. In this work, different technologies for nano structuring are introduced, along with the principle of the five-beam interference pattern model. Several images of interference results obtained by the five-beam interference pattern model are shown and some of their possible applications are discussed. Three-beam interference patterns and five-beam interference patterns are formed using a laser beam that goes along the z axis which is not used commonly in other LIL models.

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.

AFM-detected apoptosis of hepatocellular carcinoma cells induced by American ginseng root water extract

American ginseng as a common and traditional herbal medicine has been used in cancer treatment for many years. However, the effect of American ginseng on the cancer cell response (i.e. apoptosis) has not been fully understood yet. Previous studies demonstrated that cellular apoptosis was associated with the changes of mechanical and morphological properties. Therefore, in this study, mechanical and morphological characterizations were carried out by both atomic force microscope (AFM) and inverted optical microscope to investigate the apoptosis of hepatocellular carcinoma (SMMC-7721) cells affected by American ginseng root water extract (AGRWE). The results showed that the cells treated with AGRWE exhibited significantly larger surface roughness, height and elastic modulus values than control group. Moreover, those parameters were upregulated under the higher concentration of AGRWE and longer culture time. Consequently, it indicates that the mechanical and morphological properties can be used as the apoptotic characteristics of SMMC-7721 cells. Also, the increased surface roughness and elastic modulus of cells under the AGRWE treatment have shown that the apoptosis of SMMC-7721 cells can be enhanced by AGRWE. This will provide an important implication for hepatocelluar carcinoma treatment and drug development.

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.

Nanolocalization of features in the patterns produced by Four-beam Laser Interference Lithography

This paper presents a method for nanolocalization of features in the patterns produced by Four-beam Laser Interference Lithography (FBLIL) using image processing techniques. In the work, the least-squares fitting method was used for nanolocalization of features, having obtained the main parameters of the pattern by both simulation and experiment. The results have shown that the method is useful for the nanolocalization of the pattern features in laser interference lithography.

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.