Separation Of Micro Research Articles

Analytical and finite element modeling of vibro-acoustic modes of a fluid-filled thick-walled hollow microcylinder and applications in low-power particle manipulation.

Nonlinear acoustic interactions such as acoustic radiation forces or acoustic streaming require high-amplitude acoustic pressure or velocity terms to generate observable effects. While at the macro-scale these effects are not widely used; due to the highly compliant microstructures, high-amplitude acoustic pressure and velocity terms have been reached in a microscopic cavity even at very low-voltage drives (1–10 Vpp). Here, vibrational and acoustic modes of a thick-walled fluid-filled hollow cylindrical glass capillary are introduced. Vibrations are coupled to the capillary through a laser cut, C-shaped lead zirconate titanate plate. Mode shapes and dispersion relationships are obtained both analytically and from finite element modeling in ANSYS. Analytical modeling of the microcavity resonator shows excellent agreement with the computational models developed in ANSYS and the experimental results. Coupling of the vibrational modes of the capillary to the fluid enclosed plays an essential role in manipulation and separation of micro- and nanoparticles and biological entities in acoustically excited portable microfluidic platforms. In this regard, proper modeling of the vibroacoustic modes enables calculation of acoustic radiation force field generated inside the microfluidic capillary. Experimental results on particle collection and separation will be presented at the meeting.

Mode I Fracture Surface of Granite: Measurements and Correlations with Mechanical Properties

This paper deals with the experimental characterization of the fracture surface of granite, obtained from direct tensile tests. The objective is to address the dependence of Mode I fracture energy on the fracture surface's roughness, as well as to analyze the fracture propagation process based on the surface features. In addition, the influence of microstructural aspects on the fracture surface is also discussed. Different types of granites were studied, similar to the ones used in the fabric of ancient buildings, with distinct petrographical characteristics. The fracture surfaces were inspected with a novel 3D laser topographical inspection system aiming at acquiring the texture of fracture surface profiles at various locations on the surface. The relief of the fracture surfaces was characterized by means of classical parameters, namely, mean roughness and root-mean-square roughness. A deeper analysis was carried out by the separation of micro- and macroroughness regimes. This study reveals a clear linear trend between fracture energy and mean microroughness. Additionally, it was found that microstructural aspects, like planar anisotropy and grain size, as well as weathering state, influence the fracture surface. The results allow further understanding of the fracture process in quasi-brittle materials and contribute to the assessment of the mechanical characterization of granite under tension.

Tensions at Liquid Interfaces: A General Filter for the Separation of Micro-/Nanoparticles

In this letter, we put forward a new strategy for the separation of micro-/nanoparticles with different sizes and densities by using the tensions at liquid interfaces. The interactions between particles and a liquid-liquid interface have been analyzed. Furthermore, we applied our strategy to the separation of two size-distributed Cu2O particles by using the water and n-pentanol interface, which demonstrates the feasibility of the proposed separation method.

A constrained sequential-lamination algorithm for the simulation of sub-grid microstructure in martensitic materials

We present a practical algorithm for partially relaxing multiwell energy densities such as pertain to materials undergoing martensitic phase transitions. The algorithm is based on sequential lamination, but the evolution of the microstructure during a deformation process is required to satisfy a continuity constraint, in the sense that the new microstructure should be reachable from the preceding one by a combination of branching and pruning operations. All microstructures generated by the algorithm are in static and configurational equilibrium. Owing to the continuity constraint imposed upon the microstructural evolution, the predicted material behavior may be path-dependent and exhibit hysteresis. In cases in which there is a strict separation of micro- and macrostructural lengthscales, the proposed relaxation algorithm may effectively be integrated into macroscopic finite-element calculations at the sub-grid level. We demonstrate this aspect of the algorithm by means of a numerical example concerned with the indentation of a Cu–Al–Ni shape memory alloy by a spherical indenter.

Microdevices for separation, accumulation, and analysis of biological micro- and nanoparticles

Microfabrication and performance of a novel microsystem for separation, accumulation and analysis of biological micro- and nanoparticles is reported. Versatile chip functions based on dielectrophoresis and microfluidics were integrated to isolate particles from complex sample solutions such as serum. A bead-based assay for virus detection is proposed. Separation of micro- and sub-mum beads employing dielectrophoretic deflector and bandpass structures is demonstrated. Individual antibody coated beads with hepatitis A virus bound to their surface were trapped by negative dielectrophoresis in a field cage and analysed by fluorescence microscopy.

Size-selective separation of micro- and nano-particles

Size-selective separation of micro- and nano-particles

Anion-Exchange Separation of Germanium from Arsenic(III and V) and Other Elements in Hydrochloric Acid-Acetic Acid Medium

Abstract In this paper a highly selective method is described for the separation of micro- and milligram amounts of germanium from arsenic(III and V) as well as from many other metal ions by means of the strongly basic anion-exchange resin Dowex 1-X8. This separation procedure is based on the preferential elution of germanium tetrachloride from a column of this resin by means of a mixture consisting of 90% acetic acid and 10% 9 N hydrochloric acid, under which condition arsenic, iron, cobalt, copper, manganese, molybdenum, lead, bismuth, and several other metal ions are strongly retained by the resin as anionic chlorocomplexes while germanium passes into the eluate practically unadsorbed. For the final photometric determination of germanium directly in the eluate, a modification of the phenylfluorone method is employed.