Nafarizal Nayan

Biophysical characteristics of cells cultured on cholesteryl ester liquid crystals

This study aimed at examining the biophysical characteristics of human derived keratinocytes (HaCaT) cultured on cholesteryl ester liquid crystals (CELC). CELC was previously shown to improve sensitivity in sensing cell contractions. Characteristics of the cell integrin expressions and presence of extracellular matrix (ECM) proteins on the liquid crystals were interrogated using various immunocytochemical techniques. The investigation was followed by characterization of the chemical properties of the liquid crystals (LC) after immersion in cell culture media using Fourier transform infrared spectroscopy (FTIR). The surface morphology of cells adhered to the LC was studied using atomic force microscopy (AFM). Consistent with the expressions of the integrins α2, α3 and β1, extracellular matrix proteins (laminin, collagen type IV and fibronectin) were found secreted by the HaCaT onto CELC and these proteins were also secreted by cells cultured on the glass substrates. FTIR analysis of the LC revealed the existence of spectrum assigned to cholesterol and ester moieties that are essential compounds for the metabolizing activities of keratinocytes. The immunostainings indicated that cell adhesion on the LC is mediated by self-secreted ECM proteins. As revealed by the AFM imaging, the constraint in cell membrane spread on the LC leads to the increase in cell surface roughness and thickness of cell membrane. The biophysical expressions of cells on biocompatible CELC suggested that CELC could be a new class of biological relevant material.

Interfacial study of cell adhesion to liquid crystals using widefield surface plasmon resonance microscopy

Widefield surface plasmon resonance (WSPR) microscopy provides high resolution imaging of interfacial interactions. We report the application of the WSPR imaging system in the study of the interaction between keratinocytes and liquid crystals (LC). Imaging of fixed keratinocytes cultured on gold coated surface plasmon substrates functionalized with a thin film of liquid crystals was performed in air using a 1.45NA objective based system. Focal adhesion of the cells adhered to glass and LC were further studied using immunofluorescence staining of the vinculin. The imaging system was also simulated with 2×2 scattering matrix to investigate the optical reflection of the resonant plasmonic wave via the glass/gold/cell and glass/gold/LC/cell layers. WSPR imaging indicated that keratinocytes are less spread and formed distinct topography of cell-liquid crystal couplings when cultured on liquid crystal coated substrates. The simulation indicates that glass/LC shifted the surface plasmon excitation angle to 75.39° as compared to glass/air interface at 44°. The WSPR microcopy reveals that the cells remodelled their topography of adhesion at different interfaces.

Effects of trypsin and cytochalasin-B treatments to cell traction forces

This study aimed at characterizing the responses and cell traction forces of keratinocytes after treated with trypsin and cytochalasin-B using a liquid crystal based cell traction force transducer. The physical restructuring of the cell and the deformation lines induced in the liquid crystal surface were profiled using phase contrast microscopy. The liquid crystal based cell traction force transducer allowed experiments involving the dissolution of the cytoskeleton via cytochalasin-B and trypsinization to identify clear differences in cell responses to the two treatments indicated that the attachment of the cells was mediated by integrins and enforced by actin filaments. This work indicates that the new liquid crystal based sensor can be used to interrogate the kinetic and cytoskeletal responses of cells to the infusion of compounds known to interact with the actin cytoskeleton and adhesion proteins.

Optimization of RF magnetron sputtering plasma using Zn target

RF magnetron sputtering is a well known technique to fabricate metal and metal oxide thin film. Basically, metal oxide thin film was achieved using the combination of inert gas and reactive gas during the sputtering deposition. Recently, the fabrication of zinc oxide (ZnO) thin film has been investigated intensively in the global scale as well as in Malaysia [1]. Zinc oxide (ZnO) is a material of great interest for short-wavelength light-emitting electro-optical nanodevices due to its wide band gap (3.37 eV) and large excitation binding energy (60 meV). Their applications is in many fields such as optoelectronics, transparent conductive oxide, solar cell and photovoltaic, sensors and etc‥ Various methods has been used to obtain and improve ZnO thin film such as sputtering, chemical bath deposition, pulsed laser deposition and chemical vapor deposition [2,3].

I DD scan test method for fault localization technique on CMOS VLSI failure analysis

One of the fashionable stress test that has been practiced in CMOS VLSI recently is known as IDDQ scan test. It has competency to be exercised as a part of failure analysis method in localization latent defect with nano scale geometry, i.e. gate oxide hole. An extension study in this field delivers proficiency on logic circuit diagnostic. Form the results obtained during the experiment, it shows that the IDD scan test can be applied effectively in triggering significant emission spot during anomalous logic transition.

Electrical and optical characteristics of atmospheric pressure plasma needle jet driven by neon trasformer

The atmospheric pressure plasma needle jet driven by double sinusoidal waveform of neon transformer is reported in this paper. The commercial neon transformer produces about 5 kV of peak sinusoidal voltages and 35 kHz of frequency. Argon gas has been used as discharge gas for this system since the discharge was easily developed rather than using helium gas. In addition, argon gas is three times cheaper than helium gas. The electrical property of the argon discharge has been analyzed in details by measuring its voltage, current and power during the discharge process. Interestingly, it has been found that the total power on the inner needle electrode was slightly lower than that of outer electrode. This may be due to the polarization charges that occurred at inner needle electrode. Then, further investigation to understand the discharge properties was carried out using optical emission spectroscopy (OES) analysis. During OES measurements, two positions of plasma discharge are measured by aligning the quartz optical lens and spectrometer fiber. The OH emission intensity was found higher than that of N2 at the plasma orifice. However, OH emission intensity was lower at 1.5 cm distance from orifice which may be due to penning ionization effect. These results and understanding are essential for surface modification and biomedical applications of atmospheric pressure plasma needle jet.

Morphology, topography and thickness of copper oxide thin films deposited using magnetron sputtering technique

Cupric Oxide (CuO) is one of the p-type metal oxide semiconductors that are suitable for use in gas sensing device. The copper oxide thin film was prepared on silicon wafer by sputtering of pure copper target at difference deposition time of 5 min, 10 min and 15 min using RF magnetron sputtering technique. Argon flow rate, oxygen flow rate, RF power and working pressure were fixed at 50 sccm, 8 sccm, 400 W and 22.5 mTorr, respectively. The influence of the deposition time towards the surface morphology, topography and thickness has been investigated. SEM and AFM analysis showed that the grain size of the films increases with the increase of deposition time. However, the surface structure of the films remains the same. In addition, it is noticed that when the deposition time increased, the surface of the films becomes rougher. The deposition rate was approximately 29 nm/min, and it was evaluated from the film thickness deposited at several times.

Difference in structural and chemical properties of sol–gel spin coated Al doped TiO2, Y doped TiO2 and Gd doped TiO2 based on trivalent dopants

In this research, pure titanium dioxide (TiO2) and doped TiO2 thin film layers were prepared using the spin coating method of titanium(IV) butoxide on a glass substrate from the sol–gel method and annealed at 500 °C. The effects on the structural and chemical properties of these thin films were then investigated. The metal doped TiO2 thin film which exists as trivalent electrons consists of aluminium (Al), yttrium (Y) and gadolinium (Gd). The anatase phase of the thin films was observed and it was found that the crystal size became smaller when the concentration of thin film increased. The grain size was found to be 0.487 to 13.925 nm. The types of surface morphologies of the thin films were nanoporous, with a little agglomeration and smaller nanoparticles corresponding to Al doped TiO2, Y doped TiO2 and Gd doped TiO2, respectively. The trivalent doping concentration of the thin films increased with a rising of thickness of the thin film. This can contribute to the defects that give advantages to the thin film when the mobility of the hole carriers is high and the electrons of Ti can move easily. Thus, Ti3+ existed as a defect state in the metal doped TiO2 thin film based on lattice distortion with a faster growth thin film that encouraged the formation of a higher level of oxygen vacancy defects.

Effect of working power and pressure on plasma properties during the deposition of TiN films in reactive magnetron sputtering plasma measured using Langmuir probe measurement

The ion, electron density and electron temperature during formation of TiN films in reactive magnetron sputtering system have been investigated for various settings of radio frequency (RF) power and working pressure by using Langmuir probe measurements. The RF power and working pressure able to affect the densities and plasma properties during the deposition process. In this work, a working pressure (100 and 20 mTorr) and RF power (100, 150 and 200 W) have been used for data acquisition of probe measurement. Fundamental of studied on sputter deposition is very important for improvement of film quality and deposition rate. Higher working pressure and RF power able to produce a higher ion density and reduction of electron temperature.

Plasma diagnostic by optical emission spectroscopy on reactive magnetron sputtering plasma –A Brief Introduction

Optical emission spectroscopy has been employed as non-invasive plasma diagnostics method and it is to detect the light emission during titanium nitride deposition using magnetron sputtering plasma discharge. The optical emission from argon and titanium were used to observe the ionization ratio of each element during the discharge. Then, the optical emission of nitrogen spectrum was used for the calculation of gas rotational temperature by using a simple formula and it was evaluated at various discharge conditions. A comparative of two different spectrometers resolution have been used for the determination of gas temperature. The results showed that the evaluated temperatures were almost the same as expected in high-pressure magnetron sputtering plasmas even when using low-resolution of spectrometer.