Vytenis Naginevicius’s research while affiliated with Kaunas University of Technology and other places

Today, microfluidics has become a revolutionary interdisciplinary topic with considerable attention in a wide range of biotechnology applications. In this research work, a numerical investigation of a microfluidic micromixer is carried out using a hybrid actuation approach with different micropillar shapes and gaps. For this purpose, COMSOL Multiphysics v.5.2. is used with three different physics, such as thermoviscous acoustic physics to solve acoustic governing equations, laminar physics to solve fluid flow governing equations, and diluted transport species to solve mixing governing equations. The simulations were carried out at different Reynolds numbers such as 2, 4, 6, 8, 10, and 12 with an oscillation frequency of 15 kHz. The results were in the form of acoustic characteristics such as acoustic pressure, acoustic velocity, acoustic stream, mixing index, and fluid flow behaviour at various Reynolds numbers. The results revealed that the inclusion of micropillars improved the mixing performance and strength of the acoustic field, resulting in an improvement of the mixing performance compared to the case without micropillars. In addition, the mixing performance is also investigated at different Reynolds numbers, and a higher mixing index is investigated at lower Reynolds numbers. Moreover, it was also investigated that blade-shaped micropillars with 0.150 mm gaps deliver the best results compared to the other cases, and the maximum and minimum values of the mixing index are 0.97 and 0.72, respectively, at Reynolds number 2. The main reason behind this larger mixing index at low Reynolds numbers is due to the inclusion of micropillars that enhance the diffusion rate and contact area, leading to the homogenisation of the heterogeneous fluids in the microchamber. The obtained results can be extremely helpful for the design and modifications of a hybrid microfluidics micromixer.

In this context, the nonlinear bending investigation of a sector nanoplate on the elastic foundation is carried out with the aid of the nonlocal strain gradient theory. The governing relations of the graphene plate are derived based on the higher-order shear deformation theory (HSDT) and considering von Karman nonlinear strains. Contrary to the first shear deformation theory (FSDT), HSDT offers an acceptable distribution for shear stress along the thickness and removes the defects of FSDT by presenting acceptable precision without a shear correction parameter. Since the governing equations are two-dimensional and partial differential, the extended Kantorovich method (EKM) and differential quadrature (DQM) have been used to solve the equations. Furthermore, the numeric outcomes were compared with a reference, which shows good harmony between them. Eventually, the effects of small-scale parameters, load, boundary conditions, geometric dimensions, and elastic foundations are studied on maximum nondimensional deflection. It can be concluded that small-scale parameters influence the deflection of the sector nanoplate significantly.

The adaptive control of metal cutting processes is a logical extension of the CNC systems. In CNC systems of metal-cutting processes the machining variables (e.g., the cutting speed and feedrate) are prescribed by the part programmer. The determination of these variables depends on experience and knowledge regarding the workpiece and tool materials, coolant conditions, and other factors.The determination of these operating parameters depends on experience and knowledgeregarding the workpiece and tool materials, coolant conditions, and other factors. By contrast,the main idea in adaptive control is the improvement of the production rate, or the reductionof machining costs, by calculation and setting of the optimal operating parameters duringmachining itself. This calculation is based upon measurements of process variables in real time and is followed by a subsequent on-line adjustment of the machining variables subject to constraints with the objective to optimize the performance of the overall system.The adaptive control is basically a feedback system, in which the operatingparameters automatically adapt themselves to actual condition of the process. AC system formachine tools can be classified into two categories:1.Adaptive control with optimization(ACO);2.Adaptive control with constraints(ACC);ACO refers to systems in which a given performance index (usually an economicfunction) is extremized subject to process and system constraints. With ACC, the machiningparameters are maximized within a prescribed region bounded by process and systemconstraints, such as maximum torque or power. ACC systems, however, do not use aperformance index. In both systems an adaptation strategy is used to vary the operatingparameters in real time cutting progresses. Although there has been considerable research onthe development of ACO systems, few, if any, of these systems are used in practice. The major problems with such systems have been difficulties in defining realistic indexes of performance and the lack of suitable sensors which can reliably measure on-line thenecessary parameters in a production environment. The objective of most AC systems isimprovement in productivity, which is achieved by increasing the metal removal rate (MRR)during rough cutting operations. The increases in productivity range from approximately 20 to 80 percent and clearly depend on the material being machined and the complexity of the part tobe produced.

The main aim of the paper is to present replication of computer-generated microstructure on the piezoelectric nano composites with PZT and PMMA (Polymethyl methacrylate) and fabrication of the nanoporous aluminum oxide membrane with nanopores. In this paper computer-generated hologram is produced and replicated on the piezoelectric nano composites by using thermal replication process in the form of micro channels. Nanoporous aluminum oxide membrane fabricated with two step anodization by using custom experimental setup and hexagonal pores with 80 nm diameter and 110 nm interpore distance.

The main aim of the paper is to prepare a nonporous aluminum oxide membrane which will be used as a micro/Nano filter in biomedical micro hydraulic device or system by using piezoelectric material actuator acting as a vibroactive member to excite the aluminum oxide membrane. In order to identify the aluminum oxide membrane could be used as active nano filter for filtration of any kind of particle membrane was excited at frequency range of 5 kHz to 100 kHz and the distribution of vibration on the membrane was presented in the paper. On the other hand, it is shown that this type of membrane could be used as a particle separation of fluid separation in the micro hydraulic devices in biomedical. Analysis of transportation of bioparticles through the membrane filter were analyzed using developed coherent optics principles.

The paper presents the construction of vibration - assisted spring-loaded batcher, its principle of operation is described, the spring-loaded batcher transverse vibration forms and the dependence of the vibration frequency and the amplitude on the dosed liquid are introduced. Mathematical modelling and the experimental results are presented in the paper.

Construction of a novel vibratory tabular valve- and its design optimization is presented in the paper. The principle of the system operation is based on the effect of dynamic positioning of a steel ball in a vibrating tube. Theoretical analysis of the stability of this non-linear system is coupled together with the experimental study of an operating valve. Laser holographic interferometry is used for the identification and optimization of working regimes of the system.