Effect of Cilia Orientation in Metachronal Transport of Microparticles

A biomimetic approach is used to generate a directed transversal transportation of micron-sized particles in liquids based on the principle of cilia-type arrays in coordinated motion. Rows of flaps mimicking planar cilia are positioned off-centre along an array of cavities covered with membranes that support the flaps. These membranes are deflected from a concave to a convex shape and vice versa by pneumatic actuation applying positive and negative pressures (relative to the ambient) inside the cavities. As a result, the flap on top of the membrane tilts to the left or right within such a pressure cycle, performing a beat stroke. Since each cavity can be addressed in the device individually and in rapid succession, waves of coordinated flap motion can be run along the wall. Such metachronal waves are generated and transport of particles along the cilia surface is achieved in both symplectic and antiplectic direction. It is shown that the initial tilt of the flaps relative to the wall-normal determines the direction of transport

Experimental and numerical study of interaction between particle loaded fluid and a rough wall with micropillars

© 2014 Elsevier Ltd. All rights reserved. Experimental and numerical studies of the behavior of a slurry in a shear flow over a rough surface with a defined micro-structure are presented. A new ring shear device was built which contains an optically transparent test chamber. Its bottom wall contains arrays of micro-cantilever force sensors simulating a defined surface roughness created by deep-etching of micro-pillars in a silicon wafer. The results of visual observation of the interaction of the suspension with the structured surface during severe deformation are shown. Observations comprise the liquid phase motion, i.e., the interaction between the liquid phase and solid particles, the movement of separate particles and their interactions with the micro-pillars. Abrupt changes in rotational motion and translational velocity of particles are observed that induce mutual collisions and successive formation and break-up of cluster structures of various types. In addition to the experiments the process was simulated with discrete element (DEM) simulations. Many characteristics found in the experiments are reproduced by the simulations. Furthermore the physical quantities of the process like contact forces or velocities can be quantified which helps us to develop more detailed models of the abrasive behavior of slurries

Flow and motion behavior of particle suspensions in shear flow over a rough surface

The paper discloses the experimental study results of the behavior of a thin layer of low concentrated slurry in a shear flow over a rough surface with a defined structure of the bottom wall. A new ring shear device was built which contains an optically transparent test chamber of which the bottom wall contains arrays of micro-cantilever force sensors simulating a defined surface roughness. It was created by deep-etching of micro-pillars in a silicon wafer. The results of visual observation of the interaction of the suspension with the structured surface during severe deformation are shown. Observation covered the liquid phase motion by micro-PIV, the interaction between the liquid phase and solid particles, the movement of separate particles and their mutual interaction. The contact interactions between particles and micro-pillars are exemplified. The abrupt changes in rotational motion and translational velocity of particles induce mutual collisions and continuous formation and break-up of cluster structures of various types. © 2013 WIT Press

Transmission and diffraction of impulse waves in foam media with cavities

Widespread use of foam materials in construction, which makes it possible to significantly reduce the cost and facilitate construction, caused increasing interest in the development of methods studying the stress state of such materials during action of various dynamic loads triggered by technological and mechanical influences. Research of transmission of waves that arises from the effects of such influences will give an opportunity to more accurately assess the strength of such structural elements and the effectiveness of their use. The aim of the work is to develop a method for studying the transmission and diffraction of elastic impulses in foam materials with tunnel cavities of an arbitrary cross-section.In order to solve the problem the boundary integral equations method was used together with the time Fourier transform, which made it possible to obtain integral equations in a complex form for the Cosserat pseudo-continuum. Using the developed approach the research of transmission and diffraction of weak shock waves on tunnel cavities in foam media was carried out based on the analysis of fields of dynamic and radial stresse

Production of retardation film with pixel strusture

At present the commercial success of LC displays is achieved due to the high characteristics of quality: viewing angles, contrast, price, etc. For example, LC display have been used for creation of 3D images by means of forming images on the display for the left and right eye and using of polarizing glasses for the left and right eye. It allows us to see the resulting 3D image. Such a system can be implemented by means of using of a pattern phase retardation film which is placed on the display screen. The retardation film is a structured phase plate with display pixels order resolution which allows to form lines of images for the left and right eye without loss of image quality

Fluid transport via pneumatically actuated waves on a ciliated wall

To manipulate fluids actively a pneumatically actuated micro membrane device is developed to generate a directed transversal fluid transport in a liquid layer next to the wall. The biomimetic approach is based on the principle of cilia-type arrays that generate a mean flow by travelling wave activation. Rows of long flaps, which mimic the comb row of a ctenophore, are positioned off-centre along a row of cavities. Each cavity is covered by a flexible membrane that supports the flaps. The membranes with the flaps on top are deflected by applying a well-defined pressure profile to the cavities under the membranes such that an individual beat can be generated for each flap. Flow visualization experiments were carried out under the conditions of travelling waves. The results show a mean velocity profile that resembles that of a wall-jet. Mixing effects with increased retention times of the fluid occur in the vicinity of the membrane surfaces

Potential of Antifungal Drugs as Photosensitizers

In the present work, using commercially available formulation of polyene antifungal antibiotic amphotericin B, it is shown that its antifungal activity could be enhanced in combination with optical radiation corresponding to the absorption band of amphotericin B due to photodynamic effect. It is assumed that the radical processes dominate in the mechanism of photodynamic action in the presence of amphotericin B. Keywords: Amphotericin B, antimicrobial/antifungal photodynamic therapy (aPDT), lactate dehydrogenase (LDH), singlet oxygen, laser, LED

Calculation of the stability of composite rods according to the non-classical bending model

The problem of the effect of deformations of transverse shear and transverse compression on the value of the critical stress in the problem of the loss of stability of a transversely isotropic rod is considered. The fourth-order differential equation of the nonclassical bending model of rods is applied. Formulas for the critical stress are obtained, as well as numerical results for rods made of different material

Biological Effect of Continuous, Quasi-Continuous and Pulsed Laser Radiation

In this work, for the first time, comparative studies of biological activity of low intensity continuous, quasi-continuous and pulsed laser radiation of nano- and picosecond time ranges with the same average power density are carried out. It is shown, that, despite the significant differences in peak values of intensity of acting factor, both continuous and quasi-continuous radiation and radiation of nano- and picosecond ranges are able to have both stimulating and inhibiting effects on all investigated parameters of functional activity of biological systems in a certain range of dose rates. The ability of laser radiation of near infra-red spectral region (800 - 1340 nm) located out the absorption bands of main chromophores of cells to have regulatory effect on biochemical processes that control the hatching of branchiopod crustaceans Artemia salina L. upon irradiation of their cysts is revealed. The role of molecular oxygen and water as acceptors of laser radiation is discussed. Keywords: Low intensity laser radiation, Laser activation, Biological activity, Zooplankton Artemia salina L., Sturgeon sperm

Comprehensive Study of Ni Nanotubes for Bioapplications: From Synthesis to Payloads Attaching

Due to the Ni nanotubes’ shape anisotropy, low specific density, large specific surface, and uniform magnetic field, they have been offered as carriers for targeted delivery of drug or protein and the process of their formation from synthesis stage to the stage of surface modification and protein attaching has been demonstrated. Some steps to hasten their biomedical application have been applied. First, to have full control over the carrier dimensions and structure parameters, electrodeposition method in pores of polyethylene terephthalate template has been applied. Second, to understand the scope of Ni nanostructures application, their degradation in media with different acidity has been studied. Third, to improve the biocompatibility and to make payloads attachment possible, nanotubes surface modification with organosilicon compound has been carried out. At last, the scheme of protein attaching to the nanostructure surface has been developed and the binding process was demonstrated as an example of the bovine serum albumin