Vytautas Jurenas

Microsystems for the Effective Technological Processes

Piezoelectric composite material whose basic element is PZT is developed. It allows controlling the optical parameters of the diffraction grating, which is imprinted in it. In addition, the sensitivity of the designed element is increased using silver nanoparticles, thus surface plasmon resonance effect appears. The developed technological route of the production of complex 3D microstructure, from designing it by the method of computer generated holography till its physical 3D patterning by exploiting the process of electron beam lithography and thermal replication, is presented. The experimental technology for the better quality of complex microstructure replicas based on high frequency excitation in the mechanical hot imprint process was proposed and implemented.

Development of Traveling Wave Actuators Using Waveguides of Different Geometrical Forms

The paper covers the research and development of piezoelectric traveling wave actuators using different types of the waveguides. The introduced piezoelectric actuators can be characterized by specific areas of application, different resolution, and torque. All presented actuators are ultrasonic resonant devices and they were developed to increase amplitudes of the traveling wave oscillations of the contact surface. Three different waveguides are introduced, that is, symmetrical, asymmetrical, and cone type waveguide. A piezoelectric ring with the sectioned electrodes is used to excite traveling wave oscillations for all actuators. Operating principle, electrode pattern, and excitation regimes of piezoelectric actuators are described. A numerical modelling of the actuators was performed to validate the operating principle and to calculate trajectories of the contact points motion. Prototype actuators were made and experimental study was performed. The results of numerical and experimental analysis are discussed.

Rational Design Approach for Enhancing Higher-Mode Response of a Microcantilever in Vibro-Impacting Mode

This paper proposes an approach for designing an efficient vibration energy harvester based on a vibro-impacting piezoelectric microcantilever with a geometric shape that has been rationally modified in accordance with results of dynamic optimization. The design goal is to increase the amplitudes of higher-order vibration modes induced during the vibro-impact response of the piezoelectric transducer, thereby providing a means to improve the energy conversion efficiency and power output. A rational configuration of the energy harvester is proposed and it is demonstrated that the new design retains essential modal characteristics of the optimal microcantilever structures, further providing the added benefit of less costly fabrication. The effects of structural dynamics associated with advantageous exploitation of higher vibration modes are analyzed experimentally by means of laser vibrometry as well as numerically via transient simulations of microcantilever response to random excitation. Electrical characterization results indicate that the proposed harvester outperforms its conventional counterpart (based on the microcantilever of the constant cross-section) in terms of generated electrical output. Reported results may serve for the development of impact-type micropower generators with harvesting performance that is enhanced by virtue of self-excitation of large intensity higher-order mode responses when the piezoelectric transducer is subjected to relatively low-frequency excitation with strongly variable vibration magnitudes.

The effect of the teeth bleaching with 35% hydrogen peroxide on the tensile bond strength of metal brackets

The objective of this study was to determine the effects of teeth bleaching on the tensile bond strength of metal brackets bonded with light-curing adhesive system to the human enamel. 40 recently extracted human permanent molars were used for the study. The mesial buccal surface of each tooth was used as a control group and the distal buccal surface was used as an experimental group. Control group surfaces were not submitted to bleaching, while experimental group surfaces were bleached with in-office bleaching material containing 35% hydrogen peroxide. 30 days after the bleaching, identical premolar metal brackets were bonded to each surface using light-curing adhesive. Both groups were submitted to a tension test, using a universal machine. The tensile bond strength of brackets bonded to the bleached enamel was 15% lower than that of brackets bonded to the unbleached enamel. After debonding, more adhesive was left on the bracket base in experimental group than in the control group. The conclusion of this study was that bleaching with an in-office bleaching material containing 35% hydrogen peroxide reduced the tensile bond strength of orthodontic bracket adhesive to the enamel surface.

Development of Microsystems Multi Physics Investigation Methods

The theoretical and experimental methods for the investigation of microsystems multi physic processes are presented. The FEM method for the analysis of MEMS in digital environment in combination with experimental data from holographic interferometry is developed. Numerical–experimental method for evaluation of geometrical parameters and their usage for characterization of microstructures is presented. In order to optimise hot imprint method in polycarbonate, an elasto-plastic material model for simulation of microstructures hot imprint method is developed.

MOEMS-Assisted Radial Pulse Measurement System Development

Blood pressure is the first assessment of blood flow and still is the easiest parameter to measure. Examination of wrist radial pulse is non-invasive diagnostic method, which takes a very important place in traditional Chinese medicine. Hence, it lacks the consistency and reliability, which limits practical application in clinical medicine. Thus, the quantitative characteristics of the method of the wrist pulse diagnosis is a prerequisite for its further development and wide use. Noninvasive CCD sensor based on a hybrid measurement systems for the analysis of the radial pulse signals is developed. Various input pressure and fluids of different viscosity are used in the assembled artificial circulation system to test the effectiveness of laser triangulation technology to improve the detection sensitivity by a microfabricated MOEMS placed on a synthetic vascular graft and on the human wrist. MOEMS design methodology is presented. The simulation results provide the right to choose the form of the membrane. Technological process of formation of MOEMS is performed using advanced microfabrication technology. In “in vitro” and “in vivo” measurement results are adequate and suggest practical relevance of the proposed methodology.

MEMS Applications for Obesity Prevention

Accurate measurements of the dynamics of the human body begins with the measurement data by filtering the acceleration signal evaluation taking into account the different types of human daily physical activity. Considering acceleration measuring device attached several location areas are defined on the body. The methodology of the design of micro acceleration measuring device is presented. The adequacy of accelerometer mathematical model to the physical tested experimentally using a special technique, which consists of six CCD cameras. Methodology and a special method for qualitative analysis of the human body surface tissue motion is presented. Multi level computational model assess the rheological properties of the human body surface. Interesting behavior is observed when comparing the two stages of the jump: the upper position when the velocity is zero, and the maximum speed during landing. Simulation results show that reduced surface tissue rheological model is independent of belt tension force, which is used for mounting the device. Qualitative evaluation of vertical jump, proved that the disregard of human body surface tissue rheological properties are a source of errors (up to 34%) in the analysis of human body movement.

Analysis of Compact Bone Vibration Assisted Drilling

Bone drilling is often used in trauma care, orthopedic and other type of surgical procedures. The elevated temperatures caused by friction may lead to temperature induced bone necrosis. This paper presents an analysis of the effect vibration assisted drilling has on the drilling temperature of the compact bone.The experimental setup was developed and two-type experiments have been conducted. The main aim was to analyze the low frequency vibrations assisted drilling effect on the drilling temperature of poly-methyl methacrylate (PMMA) and bone samples. The temperatures at the exit hole were measured using the thermal camera. The rotational speed of the drill, applied force, parameters of the drill and the samples were considered as constant, whereas the amplitude and frequency of vibrations were varied during the experiments. The obtained experimental data showed the decrease in the drilling temperatures of the vibrated bone samples, as compared to the conventional drilling. It should be noted that further investigation and research related to the vibration assisted drilling should be carried out using different type of bone samples and experimental conditions.

Investigation of Dynamics of Laser Shutter System

In this paper, the investigation of piezoelectric unimorph laser shutting system transient vibrations damping is presented. A magnetic force technique and magneto-rheological fluid (MRF) is used for the damping of transient vibrations of the piezoelectric unimorph shutter. A methodology is presented for the analysis and design optimization of piezoelectric unimorph actuator used for laser beam shutting systems. The magnetically coupled piezoelectric unimorph cantilever and disc type piezoelectric unimorph motions are analyzed using a one-dimensional forced harmonic oscillator with a non-linear magnetic spring and MRF damper setting. Using a magneto-rheological effect for damping of transient vibrations the piezoelectric unimorph shutter has been experimentally determined.

Experimental investigation of waveguide dynamics for the medical invasion treatment

The aim of the article is to introduce into usage of waveguide for the medical invasion treatment and to provide methods that allow investigating the vibrations of the stainless steel waveguide by combining non-contact techniques with the state-of-the-art multiphysics software. The vibrations of the waveguide, used in surgery are examined by the aids of the hybrid numerical-experimental techniques, acoustic emission method, holographic interferometry technique and vibrometer based on Doppler shift of backscattered laser light. The virtual modeling of the waveguide is used by the Comsol Multiphysics software.