Browsing by Subject "Digital holographic microscopy"

Now showing 1 - 5 of 5

Open Access
Detection of Calcium-induced morphological changes on RBCs by digital holographic microscopy and blinking optical tweezers
(IEEE, 2016) Rad, V. F.; Tavakkoli, R.; Moradi, Ali-Reza; Anand, A.; Javidi, B.
Ca+2 level in the circulating red blood cells (RBCs) takes part not only in controlling biophysical properties, but also affects the membrane composition, and its morphological and rheological properties. Excessive accumulation of Ca2+ within the cells is associated with a number of important pathological diseases. In this paper, by the use of digital holographic microscopy (DHM), we quantitatively analyzed the volumetric behavior of RBC membrane under influence of excess Calcium ions. DHM in a transmission mode is an effective tool for quantitative visualization of phase objects. By deriving the associated phase changes 3D information on the morphology variation of the cells at arbitrary time scales is obtained. Individual cells are immobilized by the use of optical tweezers and are monitored live with DHM system, while the concentration of Ca2+ ions in the buffer is changed simultaneously. We utilized blinking optical tweezers, by inserting an optical chopper to modulate intensity of the trapping laser beam. Blinking optical tweezers, while keeping the cell trapped during the experiments, ensures of minimizing the photo-damage of trapping laser beam on the cell. Our experimental results are in agreement with previous biological studies and predictions, and experimental observations of living RBCs under Ca2+ influence.
Open Access
Digital holographic microscopy of phase separation in multicomponent lipid membranes
(SPIE, 2016) Rad, Vahideh Farzam; Moradi, Ali-Reza; Darudi, Ahmad; Tayebi, Lobat
Lateral in-homogeneities in lipid compositions cause microdomains formation and change in the physical properties of biological membranes. With the presence of cholesterol and mixed species of lipids, phospholipid membranes segregate into lateral domains of liquid-ordered and liquid-disordered phases. Coupling of two-dimensional intralayer phase separations and interlayer liquid-crystalline ordering in multicomponent membranes has been previously demonstrated. By the use of digital holographic microscopy (DHMicroscopy), we quantitatively analyzed the volumetric dynamical behavior of such membranes. The specimens are lipid mixtures composed of sphingomyelin, cholesterol, and unsaturated phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine. DHMicroscopy in a transmission mode is an effective tool for quantitative visualization of phase objects. By deriving the associated phase changes, three-dimensional information on the morphology variation of lipid stacks at arbitrary time scales is obtained. Moreover, the thickness distribution of the object at demanded axial planes can be obtained by numerical focusing. Our results show that the volume evolution of lipid domains follows approximately the same universal growth law of previously reported area evolution. However, the thickness of the domains does not alter significantly by time; therefore, the volume evolution is mostly attributed to the changes in area dynamics. These results might be useful in the field of membrane-based functional materials.
Open Access
Effect of Humidity on Liquid-Crystalline Myelin Figure Growth Using Digital Holographic Microscopy
(Elsevier B.V., 2016) Mosaviani, R.; Moradi, A. R.; Tayebi, L.
Dynamics of liquid-crystalline Myelin Figures (MFs) is a multifaceted issue depending on various elements, which have not been fully resolved yet. Our experimental results show that degree of humidity is influential on the initial growth and dynamics of MFs - a factor that was not been carefully considered on MF formations. In this paper, we present a systematic experimental study on the effect of humidity on MF dynamics. Quantitative analysis of MF dynamical behavior was performed using digital holographic microscopy (DHM). Our study reveals that humidifying the initial lipid reservoir has reverse effect on the rate of the growth to the extent that complete saturation of the lipid source prevents MF growth. The phenomenon is explained by the role of hydration gradient during MF formation.
Open Access
Microsphere-Assisted Super-Resolved Mirau Digital Holographic Microscopy for Cell Identification
(OSA - The Optical Society, 2017) Aakhte, M.; Abbasian, V.; Akhlaghi, E. A.; Moradi, A. R.; Anand, A.; Javidi, B.
In this paper, we use a glass microsphere incorporated into a digital holographic microscope to increase the effective resolution of the system, aiming at precise cell identification. A Mirau interferometric objective is employed in the experiments, which can be used for a common-path digital holographic microscopy (DHMicroscopy) arrangement. High-magnification Mirau objectives are expensive and suffer from low working distances, yet the commonly used low-magnification Mirau objectives do not have high lateral resolutions. We show that by placing a glass microsphere within the working distance of a low-magnification Mirau objective, its effective numerical aperture can be increased, leading to super-resolved three-dimensional images. The improvement in the lateral resolution depends on the size and vertical position of microsphere, and by varying these parameters, the lateral resolution and magnification may be adjusted. We used the information from the super-resolution DHMicroscopy to identify thalassemia minor red blood cells (tRBCs). Identification is done by comparing the volumetric measurements with those of healthy RBCs. Our results show that microsphere-assisted super-resolved Mirau DHMicroscopy, being common path and off-axis in nature, has the potential to serve as a benchtop device for cell identification and biomedical measurements.
Open Access
Optical reconstruction of transparent objects with phase-only SLMs
(Optical Society of American (OSA), 2013) Stoykova, E.; Yaraş F.; Yontem, A.Ö.; Kang H.; Onural L.; Hamel P.; Delacrétaz, Y.; Bergoënd I.; Arfire, C.; Depeursinge, C.
Three approaches for visualization of transparent micro-objects from holographic data using phase-only SLMs are described. The objects are silicon micro-lenses captured in the near infrared by means of digital holographic microscopy and a simulated weakly refracting 3D object with size in the micrometer range. In the first method, profilometric/tomographic data are retrieved from captured holograms and converted into a 3D point cloud which allows for computer generation of multi-view phase holograms using Rayleigh-Sommerfeld formulation. In the second method, the microlens is computationally placed in front of a textured object to simulate the image of the textured data as seen through the lens. In the third method, direct optical reconstruction of the micrometer object through a digital lens by modifying the phase with the Gerchberg-Saxton algorithm is achieved. © 2013 Optical Society of America.