Arvydas Palevicius

High-Frequency Excitation for Thermal Imprint of Microstructures Into a Polymer

The main objective of this paper was to propose a novel method for the formation of microstructures using high-frequency excitation during the thermal imprint process. High-frequency excitation of replica during the thermal embossing process helps to fill gaps of the stamp by the polymer. This external factor can provide a possibility to increase the quality and accuracy of the replica. Furthermore, this method does not require expensive or complex developments of the experimental setup and could be applied in most equipments of thermal imprint.

Holographic imaging technique for characterization of MEMS switch dynamics

An innovative holographic imaging technique is applied in characterization of MEMS switch non-linear dynamics. The Duffings non-linear oscillator based phenomenological model was adopted to study MEMS switch non-linear response due to the complicated contact phenomena and corresponding boundary conditions. An experimental contact measurement result of MEMS cantilever response that matches theoretical trends is provided. Non-destructive contact measurements were performed by means of quantitative nanomechnical test instruments. Non-contact holographic characterization method yielded results comparable with phenomenological model and contact measurements. The proposed holographic characterization method consists of digitized holographic measurements enhanced by the FEM eigenvector problem solution. Two cases were analyzed for simple and perturbated sinusoidal excitations that correspond to the free and contact boundary conditions, respectively.

Periodical Microstructures Based on Novel Piezoelectric Material for Biomedical Applications.

A novel cantilever type piezoelectric sensing element was developed. Cost-effective and simple fabrication design allows the use of this element for various applications in the areas of biomedicine, pharmacy, environmental analysis and biosensing. This paper proposes a novel piezoelectric composite material whose basic element is PZT and a sensing platform where this material was integrated. Results showed that a designed novel cantilever-type element is able to generate a voltage of up to 80 µV at 50 Hz frequency. To use this element for sensing purposes, a four micron periodical microstructure was imprinted. Silver nanoparticles were precipitated on the grating to increase the sensitivity of the designed element, i.e., Surface Plasmon Resonance (SPR) effect appears in the element. To tackle some issues (a lack of sensitivity, signal delays) the element must have certain electronic and optical properties. One possible solution, proposed in this paper, is a combination of piezoelectricity and SPR in a single element.

Optical characterization of diffractive optical elements replicated in polymers

Due to relative ease and cost effectiveness with which planar polymeric structures can be fabricated, diffractive optical elements replication in polymeric substrates are receiving global attention for a myriad of planar photonic and optoelectronic applications including optical interconnects. In this work we present an optical laser control method to control replication of microperiodic profile structures in polymers. Diffraction efficiency of diffraction gratings (originally produced in silicon, quartz glass and in replicated polymer substrates) was measured experimentally and estimated using linear dimensions of gratings or replica defined by atomic force microscopy (AFM). Diffraction efficiency of periodic structure was used to control the surface relief formation during the combined ion etching of crystalline Si (100) and replication of this structure using UV light hardening and hot embossing. The main experimental results are compared with the computer simulations where the standard programme (PCGrate-SX6.0) was employed.

Holographic interference method for investigation of wave transport systems

The original two coordinate step wave motors of synchronous type are analyzed. In them the output member is pushed by the standing waves excited in the input member. The input link may be a rectangular plate or a cylinder or similar. The output member is pressed to the working surface of the input member by the elastic-dissipative elements. The positions of the nodal and peak points of the input member may be changed in various ways. The created model and the performed research of the dynamics determine the characteristics of those motors. The experimental research is complicated because in the input member for example in case of a rectangular plate besides of the orthogonal standing waves the waves of various frequencies travelling and non orthogonal and of damped type arise. That is why for the solution of those problems the method is created based on the method of laser holography and the research is performed. The results of research are effective in the creation of advanced constructions of step motors of the types analyzed.

Applicability of Time-Averaged Holography for Micro-Electro-Mechanical System Performing Non-Linear Oscillations

Optical investigation of movable microsystem components using time-averaged holography is investigated in this paper. It is shown that even a harmonic excitation of a non-linear microsystem may result in an unpredictable chaotic motion. Analytical results between parameters of the chaotic oscillations and the formation of time-averaged fringes provide a deeper insight into computational and experimental interpretation of time-averaged MEMS holograms.

Polycarbonate as an Elasto-Plastic Material Model for Simulation of the Microstructure Hot Imprint Process

The thermal imprint process of polymer micro-patterning is widely applied in areas such as manufacturing of optical parts, solar energy, bio-mechanical devices and chemical chips. Polycarbonate (PC), as an amorphous polymer, is often used in thermoforming processes because of its good replication characteristics. In order to obtain replicas of the best quality, the imprint parameters (e.g., pressure, temperature, time, etc.) must be determined. Therefore finite element model of the hot imprint process of lamellar periodical microstructure into PC has been created using COMSOL Multiphysics. The mathematical model of the hot imprint process includes three steps: heating, imprinting and demolding. The material properties of amorphous PC strongly depend on the imprint temperature and loading pressure. Polycarbonate was modelled as an elasto-plastic material, since it was analyzed below the glass transition temperature. The hot imprint model was solved using the heat transfer and the solid stress-strain application modes with thermal contact problem between the mold and polycarbonate. It was used for the evaluation of temperature and stress distributions in the polycarbonate during the hot imprint process. The quality of the replica, by means of lands filling ratio, was determined as well.

Applicability of holographic technique for analysis of nonlinear dynamics of MEMS switch

Recent technological advances have enabled the fabrication of mechanical resonators down to micrometer and even nanometer scales, with super high frequencies. One particularly interesting aspect of the physical behavior of microelectromechanical systems (MEMS) is their nonlinear mechanical response at relatively small deviations from equilibrium which is caused by nonlinear electromagnetic forces, nonlinear stiffness, heat transfer porperties. It is important to understand the nonlinear behavior of MEMS in order to improve their future designs. Hybrid numerical - experimental optical techniques are applied for holographic imaging and characterization of non-linearity in micro-mechanical relays, in particular their cantilevers. The apparent simplicity of the problem is misguiding due to non-linear interaction between the cantilever and the bottom electrode. Therefore the results of optical measurements of the cantilever dynamics are inaccurate due to the shift of the fringes in time average laser holographic interferograms. Numerical modeling helps to solve non-uniqueness of the inverse problem and to validate the interpretation of the pattern of fringes.

Numerical investigation of microstructures using principles of holographic interferometry

Numerical methodology for the investigation of structures in the virtual reality is developed. This methodology is based on the principles oftime averaging laser holographic interferometry. Ability to vary the parameters ofthe virtual optical experiment enables smooth transfer to the smaller dimensions and levels of amplitudes up to the nanoscale investigations. Such type of analysis can be successfully used for different applications, starting from biological investigations of cells, up to the design of microelectronics components.

Influence of PZT Coating Thickness and Electrical Pole Alignment on Microresonator Properties

With increasing technical requirements in the design of microresonators, the development of new techniques for lightweight, simple, and inexpensive components becomes relevant. Lead zirconate titanate (PZT) is a powerful tool in the formation of these components, allowing a self-actuation or self-sensing capability. Different fabrication methods lead to the variation of the properties of the device itself. This research paper covers the fabrication of a novel PZT film and the investigations of its chemical, surface, and dynamic properties when film thickness is varied. A screen-printing technique was used for the formation of smooth films of 60 µm, 68 µm, and 25 µm thickness. A custom-made poling technique was applied to enhance the piezoelectric properties of the designed films. However, poling did not change any compositional or surface characteristics of the films; changes were only seen in the electrical ones. The results showed that a thinner poled PZT film having a chemical composition with the highest amount of copper and zirconium led to better electrical characteristics (generated voltage of 3.5 mV).