Showing 9 results for Atomic Force Microscopy
, Alireza Naderi Sohi, ,
Volume 7, Issue 2 (9-2016)
Abstract
According to the novel achievements, nanotopography and steric geometry of the microenvironment around the cells have a drastic role on their fates. Hence, fabrication of biocompatible nanostructures as the scaffolds for the cell culture and in the next step, accurate determination of their physical and geometrical characteristics is widely considered. Despite of broad utilization of Atomic Force Microscopy to investigate topological traits of sophisticated nanopatterns; its capability to characterize electrospun nanofibers has not been studied inquiringly. In the present research, chitosan nanofibers which were successfully electrospun at the optimized conditions were then evaluated using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) respectively. The results suggested that recruitment of both of these techniques have their own advantages and disadvantages. As the first noticeable issue, while the sample preparation and scanning procedure in SEM imaging may disrupt native structure of fibers, probing the sample by AFM doesn't need any pre-imaging treatment. The main application of SEM in analysis of nanofibrillar structures is the rapid survey of nanofibers shape, orientation, diameter and consistency. In the other side, three dimensional imaging by AFM makes it possible to determine whole surface roughness, roughness along fibers and woven tissue thickness. Furthermore, regarding some technical advices, AFM can be used to estimate nanofibers average diameter as well as SEM.
E. Karimi , A. Sadeghi,
Volume 10, Issue 1 (3-2019)
Abstract
Silver nanoparticles have antimicrobial activity and are used in various commercially produced products. In this study, the effects of two types of nanosilver formulations, including LS2000 and L2000 on two strains of Streptomyces and three phytopathogenic agents, Pythium aphanidermatum, Pythium ultimum and Fusarium solani were investigated. Streptomyces and phytopathogenic agents were cultured on ISP2 and PDA medium respectively supplemented with 0, 5, 10, 25, 50 and 70ppm of LS2000 and L2000. The influence of LS2000 and L2000 on mycelium of Streptomyces was investigated by atomic force microscopy (AFM). Colony forming unit (cfu) of the bacteria decreased in response to elevated concentrations of L2000. LS2000 completely inhibited growth of both strains at a concentration of 5ppm. The inhibitory effects of LS2000 on the phytopathogenic agents were more than L2000. P. aphanidermatum showed the highest tolerance to L2000 and only at 75ppm of the nanoparticles, the diameter of the colonies was decreased. High susceptibility of F. solani to L2000 caused a decrease in fungal colony diameter in lowest concentration of the nanoparticles. The growth of all phytopathogenic agents was decreased by LS2000 and completely stopped in a concentration of 50ppm. The results showed that LS2000 destroyed mycelial networks of the both bacteria in all tested concentrations. Vesicles appeared on the surface of the mycelium branches, subsequent to treatment with L2000. Based on the results, the inhibitory effects of silver nanoparticles on the beneficial soil bacteria were more than on the phytopathogenic agents. Therefore, more caution should be taken in using silver nanoparticles as a fungicide in agriculture.
Volume 14, Issue 11 (2-2015)
Abstract
In this paper, friction of the contacted surfaces with random roughness distribution in nano scale has been modeled and simulated. So, firstly the modified friction model, AMM, was derived for the contact of the flat/rough surfaces based on the JKR contact, HK friction model and random distribution of Greenwood-Williamson (GW) model. The results show, modified AMM model predict higher friction force. It is more accurate than the earlier AMM model due to considering of the surface forces. Following, the obtained model was extended for evaluating of friction between a flat particle and the rough surface, and especially for the tip of the atomic force microscopic on the rough surface. Then the effect of geometric parameters of surface such as standard deviation of the asperities height and radius of the asperities peak on the friction between tip and rough surface was done. It was observed that normal load and friction force are increased with growing of the standard deviation of the asperities height while as the friction coefficient will be reduced. Furthermore, the normal load, the friction force, and also the friction coefficient are raised by increasing of the asperity peak radius. Finally, it was observed that variation of standard deviation of the asperity height has more influence on the friction than the radius of the asperity peak
Volume 14, Issue 14 (3-2015)
Abstract
In this paper we developed and modeled elastic - plastic contact theories for soft spherical nano - bacteria to be applied in manipulation of various micro/nanobio particles based on atomic force microscopy. First, we simulated elastic contact for three types of nano - bacteria: S. epidermidis, S. salivarius and S. aureus, using Hertz contact model and finite element. Comparing simulation results of elastic contact with experimental data showed that considering elastic contact for simulating the contact of nano - bio particles is not appropriate and will yield incorrect results. Therefore, in this research, we tried to develop and simulate Chang elastic - plastic contact theory to be applied in simulation of contact mechanics for application in simulating manipulation. Comparing simulation of Chang contact theory with available experimental data and the results from contact simulation of Chen et al showed that Chang’s complete elastic - plastic theory yields desirable results. Comparing the diagram of contact radius in terms of indentation in Hertz and Chang theories showed that the created contact radius in elastic - plastic state is larger than contact radius in elastic state.
Volume 15, Issue 11 (1-2016)
Abstract
In this paper, the elastic modulus of nanocellulose/PLA nanocomposites obtained by the two methods including nanoindentation and tensile tests were analyzed. Nanocellulose extracted by Mechanical method from linter pulp fiber. Amount of usage of nanocellulose was 3 and 5% wt , as well as for improving of nanoparticles distribution in polymer matrix, masterbatch technique was used. Then the mechanical properties of nanocomposites with and without this technique were studied. Tensile test was performed in accordance with the standard method and for nanoindentation, the atomic force microscope in peak force tapping mode was used. Tensile test results showed that the use of masterbatch, improves tensile modulus, tensile strength and strain at break. Also by increasing nanocellulose percentage from 3 to 5%, in nanocomposite with master batch, the tensile strength and strain at break increased. But this increasing had not significant effect on tensile properties of nanocomposite without masterbatch. A similar trend of strength test results was observed in nanoindentation results. Based on this result, using of masterbatch in nanocomposite caused the increase in elastic modulus. The results of these two analyses were compared and tensile test showed lower modulus value than nanoindentation.
Volume 19, Issue 1 (1-2019)
Abstract
Nanotechnology deals with objects and materials in nanometer scale and it is being expanded in the field of materials tools and systems. Nowadays, human knowledge in nanotechnology is going through a commercializing path in order to provide more services. Living creatures are built of cells with 10 μm size. Some nanoparticles application in biology and medicine include drug and gene delivery, tissue engineering, and tumor destruction with heat. These procedures, which are done with nanoparticles manipulation, have two specific phase in general; in phase one, the amount of critical force and time are calculated based on dimensional and peripheral parameters. Now, it is tried to calculate nanoparticles displacement and velocity during the process in the phase two of nanoparticles manipulation. Also, in this paper, nanoparticles displacement and velocity were investigated in two dimensional space, using three main friction model namely coulomb, Hk, and lugre in phase two of nanoparticles manipulation. According to the results of this project, maximum speed and displacement was obtained, using lugre friction model and the minimum amounts in coulomb model. Also, with particles radius increase, displacement and velocity were reduced; this effect is engendered even without considering friction factor. Correspondingly, considering accuracy and validity, the coulomb model was the least accurate model and lugre was the most accurate one and the HK model was placed between these two models.
Volume 20, Issue 12 (11-2020)
Abstract
Diagnosis of cell properties to separate healthy and damaged tissues, imaging and determination of cells’ shape and different surfaces are new applications of atomic force microscopy, which have extended using of the atomic force microscopy these days. In the manipulation modeling of micro/nanoparticles, using an atomic force microscope, one of the important points, is using an appropriate and accurate contact model. Since in the 3D manipulation, micro/nanoparticle is located between the cantilever and the substrate, therefore contact theories should be divided into two parts. The first section is the contact between the substrate and micro/nanoparticle, and the other section is the contact between micro/nanoparticle and the tip of the cantilever. In this research elasticity module of the gastric cancer cells has been measured using atomic force microscopy to diagnose cancerous tissue. To do so, two Hertz and JKR contact models have been developed to extract the elasticity module. In an experimental, after isolating the cells from the gastric cancer tissue, the specimens were tested using a rectangular beam and pyramidal and spherical needles under an atomic force microscope, and the force-depth graphs were obtained. Data analysis was performed. According to obtained results, the considered cell’s elasticity module has been approximated 325±25 kPa based on the curves obtained from the comparison of experimental data from atomic force microscopy and Hertz and JKR contact theories.
Volume 22, Issue 1 (12-2021)
Abstract
Mutations in DNA and the development of mutated genes that are inherited or acquired during a personchr('39')s lifetime can cause cancer. This type of disease causes the loss of normal control of cell growth and proliferation. Breast cancer, with its prevalence in both men and women and the higher incidence of women in the female population, is one of the most important cancers in the medical community. Appearance changes in the breast, the presence of a lump, and discharge and bleeding from the nipple are signs of breast cancer. Targeted treatment of this disease reduces the complications of treatment methods. Also, recognizing the mechanical properties of the cell, such as the Youngchr('39')s modulus, and examining the changes caused by cancer in these properties will make treatment more efficient and help the pharmaceutical sciences. For this purpose, in this paper, the MCF-10 breast cell has been studied using atomic force microscopy and nanomanipulation method. Atomic force microscope is one of the efficient tools in the structural studies of biological particles with the possibility of producing images of soft tissues under different environmental conditions and in a non-destructive manner. Chung, chen and brake contact are the models used in the simulation. Finally, with the simulations performed, the Young modulus of 1200 Pa is considered for this cell. Also, considering the comparisons made with experimental work, the chen contact model has been introduced as the optimal model for extracting cellular properties.
Volume 24, Issue 5 (9-2022)
Abstract
The purpose of this research was to study the relationships between surface nanomechanical properties and agronomic traits in different sugar beet varieties (Beta vulgaris spp.). Agronomic traits were related to the indicators of seed germination stage and resistance to rhizomania; and in correspondence, a group of nanomechanical traits of inner testa of seeds were examined using an atomic force microscope. The results of parametric and non-parametric correlation analysis between agronomic and nanomechanical traits showed that the single bud wet weight had a significant negative and positive relationship with, respectively, lower surface friction and adhesion of the inner testa. Similarly, thousand shell weight had a negative correlation with upper surface elasticity, and also seed vigor had a positive correlation with upper surface friction. Spearman's rho correlation coefficient showed that resistance to rhizomania also had a significant positive correlation with the upper surface adhesion of the inner testa. Three canonical variables between the two groups of physiological and nanomechanical traits were significant (r1= 0.972 and DF= 66; r2= 0.924 and DF= 50; r3= 0.839 and DF= 36). These traits have a kind of cause-and-effect relationship and, therefore, have the potential to be used for breeding programs and plant systematic studies.
