Experimental approach to the laser machining of PMMA substrates for the fabrication of microfluidic devices

This paper deals with CO₂ laser machining of a suitable amorphous polymer (PMMA) as a flexible technique for the rapid fabrication of miniaturized structures such as microfluidic devices.A model to estimate the main dimensions (depth and width) of the grooves produced by the laser on PMMA is presented, taking into account the influence of the main process parameters (incident power, scanning speed and spot diameter). This theoretical model allows to control the engraving process showing that laser could represent a valid alternative for the production of microchannels. PMMA single-use devices are found to be easier to manufacture with respect to the conventional glass or silicon products.In a second step, IR laser vaporization is adopted for the removal of a single layer of PMMA. This is achieved using multiple overlapping sequences of straight grooves with different scanning directions. The proposed technique showed that the removal depth varied proportionally with the number of layers machined, while surface roughness is influenced by the grooves spacing and the orientation of the scanning direction between successive layers.A method for thermally bonding the PMMA sheets, constituting the 3D structure of the chip, is also presented. The combination of high temperatures and low bonding pressures makes it possible to generate a bulk junction enabling good performances in terms of sealing characteristics.     

Numerical calculations for the characteristics of a waveguide isolator flange in the millimeter range

Numerical calculations are made for an isolator based on a waveguide T circulator in the 32.0–38.0 GHz range, for various parameters of the ferrite-dielectric insert. The way in which the isolator characteristics depend on the position of the insert inside the junction and on the coefficient and reflection and phase of an absorbing load in a lateral arm are investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 11, pp. 1662–1668, November, 1978.     

Simple fabrication of an antireflective hemispherical surface structure using a self-assembly method for the terahertz frequency range

A hemispherical surface structure was fabricated on a sapphire substrate by utilizing a self-assembly and spin-coating process for a terahertz (THz) antireflection coating. The self-assembled glass spheres and spin-coated material led to a gradual change in the effective refractive index. The aspect ratio of the hemispherical surface structure was controlled easily by adjusting the thickness of the B-staged bisbenzocyclobutene used as a coating. The reflectance of the fabricated hemispherical surface structure, having a period of 140 μm, exhibited low reflectance and low Fabry-Perot resonance in a THz spectral range from 0.1 to 1.9 THz.     

Advanced setup for measurement of a surface impedance of a HTSC films in a millimeter wave range

In the article a method of measurement of a surface impedance Z_s of flat HTSC samples and setup realized on its basis is considered. The method is based on use of the copper cylindrical cavity, raised on the H₀₁₁ mode, in which the researched sample replaces one of butt-end wall. Ideas realized in setup have allowed to reach practically limiting characteristics on a range and accuracy of measurement of value Z_s, for a chosen method of measurements.     

Efficient fabrication of substrates for surface-assisted laser desorption/ionization mass spectrometry using laser ablation in liquids

Substrates for the surface-assisted laser desorption ionization (SALDI) technique were prepared using electrophoresis of gold nanoparticles produced by laser ablation in liquids. Throughout the preparation, no supplemental reagent was added for the stabilization and deposition of nanoparticles. Nanoparticles were deposited more uniformly using the electrophoresis technique than using dropping of the solution. Results demonstrated that the higher uniformity of the deposition of nanoparticles improved the reproducibility of SALDI measurements. Furthermore, the thickness of the deposited nanoparticles influences the SALDI efficiency.     

Electroplating silver tetracyanoquinodimethane between gold micro-gap electrodes for the fabrication of coplanar devices, a new way to integrate material synthesis and devices fabrication within one step

In this paper we propose a method for the integration of the synthesis of silver-tetracyanoquinodimethane (AgTCNQ) and the fabrication of its devices within one step. The method was performed by electroplating Ag between gold coplanar micro-gap electrodes in tetracyanoquinodimethane (TCNQ) solution. As soon as silver was electrochemically dissolved in the TCNQ solution, it immediately reacted with TCNQ to form AgTCNQ and then deposited between Au gap electrodes. With the continuing of the reaction, the Au micro-gap electrodes were connected by AgTCNQ to form Au/AgTCNQ/Au coplanar gap devices. With this electroplating technique, series gap devices of AgTCNQ were fabricated, and the devices exhibited switching phenomena with good reproducibility. This method integrated the synthesis of AgTCNQ and the fabrication of its devices within a single step, and should be also inspirable for other charge transfer complexes. PACS 81.05.Hd; 81.20.Ka; 82.45.Aa; 82.45.Qr     

Dynamics of nonlinear precession of magnetization in a garnet ferrite film of the (100) type

The dynamics of steady-state resonant magnetization precession setting in under a transverse magnetic bias field in a garnet ferrite film of the (100) type is investigated on the basis of numerical solution of the equation describing the motion of magnetization. The existence of a steady-state dynamic mode in which the magnetization performs undamped spiral motion, as well as of large-amplitude nutation with a period being a multiple of the period of precession, is discovered.     

Parametric interaction of volume magnetostatic waves in a ferrite film with spatiotemporal modulation of the magnetic field

Effects of the resonant Bragg scattering of magnetostatic backward volume waves on the periodic structure of a conductive meander pattern with an alternating current are analyzed theoretically and compared with experiment. It is shown that unlike a static grating, a dynamic grating causes a frequency shift of the scattered wave. It is proposed that this phenomenon be utilized for effective control of the intermodal conversion of magnetostatic waves. Zh. Tekh. Fiz. 68, 105–112 (May 1998)