A. A. Evstrapov

A microfluidic chip with hydrodynamic traps for in vitro microscopic investigations of single cells

The results on making a microfluidic chip for in vitro microscopic investigations of single cells are presented. Numerical simulation of the motion trajectories of microparticles makes it possible to determine the geometry of hydrodynamic traps, their number, and the trap arrangement in a reaction chamber. According to the developed design, microfluidic chips were fabricated from a SU-8 photoresist by photolithography. The microfluidic chips have been tested to prove their operating capacity for isolating and holding K562 human myeloid leukemia cells from a sample flow and their subsequent investigation by confocal laser scanning microscopy.

Fabrication of high-aspect-ratio microstructures in polymer microfluid chips for in vitro single-cell analysis

Technologies and methods of prototyping microfluidic devices are widely used in solving many biological problems and testing of operability of new microanalytic systems. This study is devoted to analyzing the features of the formation of microstructures in SU-8 photoresist and the preparation of replicas in polydimethyl siloxane by the soft lithography method. It has been shown that the aspect ratio of the resultant microstructures is determined by their shape, size, and the force of resist adhesion to the silicon substrate and the efficiency of the circulation of the developer around microstructures. In the replication of complex microstructures, an aspect ratio of ~25 is attained. The technology considered here is used to prepare microfluidic chips with mechanical traps for fixation and the in vitro analysis of living cells.

Studying multilayer langmuir film structure by confocal laser scanning and atomic force microscopy techniques

Features of extracting information on the surface structure of a multilayer organic film from data on its optical properties and surface relief are considered. The object of investigation was a multilayer Langmuir-Blodgett film based on a prepolymer (polyamic acid salt). It is suggested that the formation of the film volume is influenced by inhomogeneities in the structure of layers.

Interaction of Optical Radiation with GaAs Nanowhisker Arrays

We have studied the reflectivity spectra of doped GaAs nanowhiskers (NWs) with various morphologies, which were grown by molecular-beam epitaxy. It is established that the character of the reflectivity spectra of NWs is determined by the shape of nanocrystals. NWs with droplike and pointlike vertices differently interact with electromagnetic radiation. Laser radiation produces a spectraly selective action on the NW array, which leads to a change in the NW height and induces “caking” of their vertices, thus modifying the reflectivity of the sample. This phenomenon can be used for the creation of local microstructures with preset characteristics in large NW arrays.

Microchannel edge formation in laser-ablated polyimide

Microchannels in polyimide (PI) have been produced by means of laser ablation (LA). The obtained results confirm the possibility of using the LA technology for the functional structure formation on PI-based microfluidic chips (MFCs). The shape of the channel edge may depend on the thermal properties of PI. This circumstance makes it possible to optimize the process of MFC fabrication by selecting a proper PI and the corresponding LA regime. Optimization of the other characteristics, such as mechanical properties and planarity of the MFCs, requires additional investigations.

Microfluidic chips for the study of cell migration under the effect of chemicals

Numerical simulation of the formation of a chemoattractant gradient in reaction chambers of a chip having different geometries enabled the determination of a structure suitable for the study of cell migration, in accordance with which hybrid polymer–glass microfluidic devices were manufactured. Verification of the procedures of alignment of cells in the reaction chamber of the chip by centrifugal force and subsequent culturing of the cells showed that microfluidic chips can be used to study cell migration under the effect of the chemoattractant gradient in vitro.

Self-organizing structure in platinum films on a Nafion type polymer membrane

The morphology of platinum films deposited onto a polymer membrane material of the Nafion type has been studied. The films with thicknesses above ∼20 nm exhibit a specific structure (morphology) that is related to the process of self-organization. The observed phenomenon is interpreted and it is established that the main mechanism responsible for the self-organization is related to the dipole interaction between clusters of the deposited catalytic metal.

High-resolution microscopy techniques for the analysis of structural inhomogeneities on the surface of organic films

Features of the analysis of the surface structure of a polyimide Langmuir-Blodgett film by means of high-resolution atomic force microscopy and confocal laser scanning microscopy are considered. It is suggested that the appearance of structural inhomogeneities on the micron and submicron levels is related to the presence of mechanical defects in substrates and to the process of thermal imidization.