Sharif Digital Repository

Nd:YAG laser treatment was used in order to increase surface cell adhesion aspects of polycarbonate (PC) films prepared via melt process. The treatment was carried out under different wavelengths and beam diameters. ATR-FTIR and UV spectra obtained from different samples before and after laser treatment in air showed that laser irradiation has induced some chemical and physical changes in surface properties. The irradiated films were also characterized using scanning electron microscopy (SEM) and contact angle measurements. Effect of pulse numbers on the surface properties was also investigated. Cell culture test was used to evaluate cell adhesion property on the PC films before and after... 

Phase morphology, state of compatibility and various properties of blends of polycarbonate (PC) with bottle-grade and fibre-grade polyethylene terephthalate (BPET and FPET, respectively) were investigated. It was found that these blends have two-phase separated morphology with partial miscibility. Scanning electron micrographs revealed separated domains of PC-rich and PET-rich zones. PC domains appear spherical increasing in size from 2 μm for PC20/FPET80 up to about 5 μm for PC60/FPET40 blend. Further increase in PC content up to 80% caused phase inversion in which FPET appears as finely dispersed domains in continuous PC matrix. Tg of PC-rich phase decreased from 153 deg;C for pure PC down... 

With significant advancements in research technologies, and an increasing global population, microfluidic and nanofluidic systems (such as point-of-care, lab-on-a-chip, organ-on-a-chip, etc) have started to revolutionize medicine. Devices that combine micron and nanotechnologies have increased sensitivity, precision and versatility for numerous medical applications. However, while there has been extensive research on microfluidic and nanofluidic systems, very few have experienced wide-spread commercialization which is puzzling and deserves our collective attention. For the above reasons, in this article, we review research advances that combine micro and nanotechnologies to create the next... 

Friction stir welding (FSW) of thermoplastic materials is an attractive but a challenging process due to inherent chemical and mechanical characteristics of polymeric materials. In the present work, thermo-mechanical models were employed to investigate the effect of processing parameters on of FSW of polycarbonate (PC). The heat flux during the joining process was localized around the PC join line and led to the formation of circular rings on the upper surface. According to the simulation results, increasing the tool rotational velocity reduced the temperature gradient and decfeased the suseptibelity of crack formation around the joint line. Cracks were formed at low frictional heats and... 

Organ-on-a-chip technology tries to mimic the complexity of native tissues in vitro. Important progress has recently been made in using this technology to study the gut with and without microbiota. These in vitro models can serve as an alternative to animal models for studying physiology, pathology, and pharmacology. While these models have greater physiological relevance than two-dimensional (2D) cell systems in vitro, endocrine and immunological functions in gut-on-a-chip models are still poorly represented. Furthermore, the construction of complex models, in which different cell types and structures interact, remains a challenge. Generally, gut-on-a-chip models have the potential to... 

Commercially available track-etched polyester membranes were used as templates to electrodeposit Co-Ni-Cu/Cu multilayered nanowires, giving room-temperature current perpendicular to plane (CPP) giant magnetoresistance (GMR) values of up to ∼12%. In contrast to similar nanowires electrodeposited in track-etched polycarbonate membranes, the GMR obtained in multilayered nanowires electrodeposited in the polyester membranes increased with decreasing Cu-layer thickness tCu, for tCu in the 2-7 nm range, indicating a lack of ferromagnetic coupling through pinholes, etc. Transmission electron micrographs showed clear evidence for smooth, parallel layer interfaces in the nanowires. © 2006 Elsevier... 

The relation between process parameters and properties of polycarbonate (PC) sheet after friction stir welding (FSW) was investigated. Effects of FSW tool rotation speed (ω), travelling speed (V), tilt angle (α) and plunge depth on material flow, joint tensile strength, flexural strength, impact energy and hardness were investigated. It is shown that at low and high levels of heat input sound joints cannot be attained. At low heat inputs, the local temperature is not high enough to decrease the viscosity of the polymer to fill the interface, and thus voids and large planar cracks are formed in the joint root and stir zone. At high heat inputs, expelling of materials due to high peak... 

The Co nanowire arrays were synthesized by electrodeposition in polycarbonate template (PC) with 4 μm thickness. Electron field emission properties of cobalt nanowires were studied for wires with different aspect ratios, R ranged between 10 and 60, while the diameter of wires was fixed about 50 nm. The field emission properties of the samples showed low turn on electric field (Eto) with values varying between 2.9 and 11.3 V/μm showing a minimum value for R = 20 (Eto < 3 V/μm). On the other hand, the enhancement factor shows a peak for nanowires length about 1 μm. Field emission data using the Fowler-Nordhiem theory showed nearly straight-line nature confirming cold field emission of... 

Fabrication of well-defined gold nanowires (GNWs) is of significant importance in many fields such as sensing applications. In this study, the electrodeposition of well-defined GNWs inside polycarbonate (PC) template has been discussed in detail. GNWs were potentiostatically electrodeposited at different filling rates. The growth of GNWs at different stages of pore filling was monitored by electrochemical measurements and field-emission scanning electron microscopy (FE-SEM). It was confirmed that under growth rates between 2.5 and 4 nm/s, GNWs with smooth ends grew uniformly inside the template without any imperfections or corrugations. The length of GNWs was electrochemically controlled to... 

Platinum nanowires (PtNWs) were electrodeposited on the polycarbonate templates (PCTs) in aqueous solution of H2PtCl6 in triply distilled water. Nanowires with diameters of 50 and 100 nanometers were electrodeposited on the same condition. The kinetics of electrodeposition process was studied by electrochemical techniques such as voltammetry and chronoamperometry methods. Increasing the scan rate, the peaks shifted to more negative potentials and the current density also increased in each peak which was typical for a diffusion-control process. The potential range for the deposition of platinum nanowires was specified and consequently the potentiostatic i-t transients were utilized to produce... 

Electrodeposition of long and well-defined gold nanotubes in polycarbonate (PC) templates is still a major concern due to pore blockage problems. In the present study, we introduce a novel method for electrodeposition of long gold nanotubes within the pores of PC templates for the first time. In order to deposit gold atoms onto the pore walls preferentially, pore walls were functionalized with a coupling agent. Short and thin Ni nanotubes were then electrodeposited at the bottom of the pores. Gold nanotubes were subsequently electrodeposited at constant potentials and low solution concentrations. The morphology of nanotubes was characterized by electron microscopy and their formation... 

During recent years centrifugal-based microfluidic devices known as Lab-on-a-CD have attracted a lot of attentions. Applications of these CD-based platforms are ubiquitous in numerous biological analyses and chemical syntheses. Mixing of different species in microscale is one of the essential operations in biochemical applications where this seemingly simple task remains a major obstruction. Application of centrifugal force, however, may significantly improve the flow agitation and mixing, especially when it is combined with the Coriolis force which acts perpendicular to centrifugal force. In this study, mixing process in minichambers located on a rotating platform under a periodic... 

During recent years centrifugal-based microfluidic devices known as Lab-on-a-CD have attracted a lot of attentions. Applications of these CD-based platforms are ubiquitous in numerous biological analyses and chemical syntheses. Mixing of different species in microscale is one of the essential operations in biochemical applications where this seemingly simple task remains a major obstruction. Application of centrifugal force, however, may significantly improve the flow agitation and mixing, especially when it is combined with the Coriolis force which acts perpendicular to centrifugal force. In this study, mixing process in minichambers located on a rotating platform under a periodic... 

Recent advances in biomaterials, microfabrication, microfluidics, and cell biology have led to the development of organ-on-a-chip devices that can reproduce key functions of various organs. Such platforms promise to provide novel insights into various physiological events, including mechanisms of disease, and evaluate the effects of external interventions, such as drug administration. The neuroscience field is expected to benefit greatly from these innovative tools. Conventional ex vivo studies of the nervous system have been limited by the inability of cell culture to adequately mimic in vivo physiology. While animal models can be used, their relevance to human physiology is uncertain and... 

Electrodeposition of gold nanowires is carried out in cyanide solution in polycarbonate templates with pore diameter of 80 nm. Electrochemical methods are utilized to characterize the gold electrodeposition and to obtain the nucleation and growth mechanism. The analysis of cyclic voltammograms shows that the electrodeposition of gold nanowires takes place under diffusion control. Current transients reveal that nucleation mechanism is instantaneous with a three-dimensional growth process. The transition-time measurements show that the gold elecrodeposition occurs as one-electron valence involved in the reaction mechanism. Charge transfer coefficient is also found to be 0.67 ± 0.01. The value... 

An impedimetric human papilloma virus (HPV) DNA biosensor based on gold nanotubes (AuNTs) in label free detection was materialized. The AuNTs decorated nanoporous polycarbonate (AuNTs-PC) template as biosensor electrode was fabricated by electrodeposition method. The single strand DNA (ss-DNA) probe was covalently immobilized onto the AuNTs-PC electrode. The hybridization of target sequences with the ss-DNA probe was observed by the electrochemical impedance spectroscopy (EIS). The biosensor showed high selectivity and could differentiate between the complementary, mismatch and non-complementary DNA sequences. The EIS measurements were matched to Randle's equivalent circuit. The... 

An impedimetric human papilloma virus (HPV) DNA biosensor based on gold nanotubes (AuNTs) in label free detection was materialized. The AuNTs decorated nanoporous polycarbonate (AuNTs-PC) template as biosensor electrode was fabricated by electrodeposition method. The single strand DNA (ss-DNA) probe was covalently immobilized onto the AuNTs-PC electrode. The hybridization of target sequences with the ss-DNA probe was observed by the electrochemical impedance spectroscopy (EIS). The biosensor showed high selectivity and could differentiate between the complementary, mismatch and non-complementary DNA sequences. The EIS measurements were matched to Randle's equivalent circuit. The... 

The Co nanowires were electrodeposited in polycarbonate membrane (PCT). SEM, TEM and XPS techniques were used to characterize the morphology, structure and size of nanowires as well as chemical composition. The influence of different mediums was studied on the optical absorption of dispersed cobalt nanowires. The absorption spectrum of cobalt nanowires in water showed a broad shoulder at 290 nm, but in ethanol solution it was not observed in the visible region of the spectra up to 200 nm. Cobalt nanowires dispersed in methanol presented a peak at 236 nm. We attribute the data to oxidation of cobalt in water and low dielectric constant of methanol relative to ethanol and water. We found...