Elingas Cekas

Composite Piezoelectric Material for Biomedical Micro Hydraulic System

‘Lab-on-a-chip’ is integrated micro-analytical system, which could perform sample pre-treatment, chemical reactions, analytical separation, detection and data handling. These platforms are able to convert biological, chemical or mechanical responses into electrical signals using the piezoelectric or piezoresistive materials. This paper discusses a piezoelectric composite material displaying its mechanical properties such as resonant frequencies, Young’s modulus and density. Nano composite polymer highlights the property of piezo effect and is suitable for formation of periodic micro scale patterns on it. These micro patterns are intended to be used as innovative functional elements in biomedical micro hydro mechanical systems such as micro channels. Thus by controlling surface configuration and the shape of active deformable polymer, pressure in microfluidic vessels can be changed and mobility of the transported bioparticles can be ensured.

Q-factor control of multilayer micromembrane using PZT composite material

Cantilever and membrane based sensors, which are capable of providing accurate detection of target analytes have been always an important research topic of medical diagnostics, food testing, and environmental monitoring fields. Here, the mechanical detection is achieved by micro- and nano-scale cantilevers for stress sensing and mass sensing, or micro- and nano-scale plates or membranes. High sensitivity is a major issue for the active element and it could be achieved via increased Q-factor. The ability to control the Q factor expands the range of application of the device and allows to achieve more accurate results. The aim of this paper is to investigate the mechanical and electrical properties, as well as, the ability to control the Q factor of the membrane with PZT nanocomposite. This multilayered membrane was formatted using the n-type <100> silicon substrate by implementing the Low Pressure Chemical Vapor Deposition (LPCVD), photolithography by using photomask with defined dimensions, deep etching, and e-beam evaporation techniques. Dynamic and electrical characteristics of the membrane were numerically investigated using COMSOL Multiphysics software. The use of the multilayered membrane can range from simple monitoring of particles concentration in a closed environment to inspecting glucose levels in human fluids (blood, tears, sweat, etc.).

Influence of binding material of PZT coating on microresonator's electrical and mechanical properties

Microresonators are fundamental components integrated in hosts of MEMS applications: covering the automotive sector, the telecommunication industry, electronic equipment for surface/material characterization and motion sensing, and etc. The aim of this paper is to investigate the mechanical and electrical properties of PZT film fabricated with three binding materials: polyvinyl butyral (PVB), polymethyl methacrylate (PMMA) and polystyrene (PS) and to evaluate applicability in control of microresonators Q factor. Micro particles of PZT powder were mixed with 20% solution of PVB, PMMA and PS in benzyl alcohol. For investigation of mechanical and electrical properties multilayer cantilevers were made. Obtained PZT and polymer paste was screen printed on copper (thickness 40 μm) using polyester monofilament screen meshes (layer thickness 50 μm) and dried for 30 min at 100°C. Electric dipoles of the PZT particles in composite material were aligned using high voltage generator (5 kV) and a custom–made holder. Electric field was held for 30 min. Surfaces of the applied films were investigated by Atomic Force Microscope NanoWizard(R)3 NanoScience. Dynamic and electrical characteristics of the multilayer were investigated using laser triangular displacement sensor LK-G3000. The measured vibration amplitude and generated electrical potential was collected with USB oscilloscope PicoScope 3424. As the results showed, these cantilevers were able to transform mechanical strain energy into electric potential and, v.v. However, roughness of PZT coatings with PMMA and PS were higher, what could be the reason of the worse quality of the top electrode. However, the main advantage of the created composite piezoelectric material is the possibility to apply it on any uniform or non-uniform vibrating surface and to transform low frequency vibrations into electricity.

Development and investigation of MOEMS type displacement-pressure sensor for biological information monitoring

The aim of this paper is to develop and investigate MOEMS displacement-pressure sensor for biological information monitoring. Developing computational periodical microstructure models using COMSOL Multiphysics modeling software for modal and shape analysis and implementation of these results for design MOEMS displacement-pressure sensor for biological information monitoring was performed. The micro manufacturing technology of periodical microstructure having good diffraction efficiency was proposed. Experimental setup for characterisation of optical properties of periodical microstructure used for design of displacement-pressure sensor was created. Pulsating human artery dynamic characteristics in this paper were analysed.

Development and analysis of new type microresonator with electro-optic feedback

Micro-resonators are fundamental components integrated in a hosts of MEMS applications: safety and stability systems, biometric sensors, switches, mechanical filters, micro-mirror devices, material characterization, gyroscopes, etc. A constituent part of the micro-resonator is a diffractive optical element (DOE). Different methods and materials are used to produce diffraction gratings for DOEs. Two-dimensional or three-dimensional periodic structures of micrometer-scale period are widely used in microsystems or their components. They can be used as elements for micro-scale synthesis, processing, and analysis of chemical and biological samples. On the other hand micro-resonator was designed using composite piezoelectric material. In case when microscopes, vibrometers or other direct measurement methods are destructive and hardly can be employed for in-situ analysis, indirect measurement of electrical signal generated by composite piezoelectric layer allows to measure natural frequency changes. Also piezoelectric layer allows to create a novel micro-resonator with controllable parameters, which could assure much higher functionality of micro-electromechanical systems. The novel micro-resonator for pollution detection is proposed. Mathematical model of the micro-resonator and its dynamical, electrical and optical characteristics are presented.

Analysis of the Influence of High-Frequency Excitation Into Quality of the Replicated Microstructure

In the present research, surface relief diffraction gratings were fabricated and investigated. The purpose of this research was to determine the collection of parameters, which influence the diffraction efficiency most positively. For replication process ultrasonic thermal embossing was selected with different manufacturing regimes (time, pressure, and temperature). Diffraction efficiencies of periodical microstructures were measured experimentally. The results have shown increase of periodical microstructure quality with the help of high-frequency oscillations during manufacturing. Combination of pressing time, pressure, temperature, and vibrations improved the efficiency of replication process.

Microstructures replication using high frequency excitation

Diffraction efficiency of grating, created by hot imprint process on the surface of polycarbonate is one of the parameters, which determines the quality of microstructure. Microstructures are replicated by using hot imprint process with and without high frequency excitation and during the quality investigation, diffraction efficiencies were measured on purpose to find microstructure of best possible optical quality, as well determine whether high frequency excitation and other process parameters during the process affect this parameter. Process parameters include: temperature, excitation frequency, force of mechanical load and duration of hot imprint process, the purpose is to determine the collection of parameters, which influences the diffraction efficiency most positively. The novel vibro active pad is proposed for microstructures replication. The main dynamical characteristics of the vibropad are presented in the paper.