Aziz Koyuncuoglu

Label-free detection of multidrug resistance in K562 cells through isolated 3D-electrode dielectrophoresis.

Dielectrophoresis (DEP), a technique used to separate particles based on different sizes and/or dielectric properties under nonuniform electric field, is a promising method to be applied in label‐free, rapid, and effective cell manipulation and separation. In this study, a microelectromechanical systems‐based, isolated 3D‐electrode DEP device has been designed and implemented for the label‐free detection of multidrug resistance in K562 leukemia cells, based on the differences in their cytoplasmic conductivities. Cells were hydrodynamically focused to the 3D‐electrode arrays, placed on the side walls of the microchannel, through V‐shaped parylene‐C obstacles. 3D‐electrodes extruded along the z‐direction provide uniformly distributed DEP force through channel depth. Cell suspension containing resistant and sensitive cancer cells with 1:100 ratio was continuously flown through the channel at a rate of 10 μL/min. Detection was realized at 48.64 MHz, the cross‐over frequency of sensitive K562 cells, at which sensitive cells flow with the fluid, while the resistant ones are trapped by positive DEP force. Device can be operated at considerably low voltages (<9 Vpp). This is achieved by means of a very thin (0.5 μm) parylene coating on electrodes, providing the advantages offered by the isolation of electrodes from the sample, while the working voltage can still be kept low. Results prove that the presented DEP device can provide an efficient platform for the detection of multidrug resistance in leukemia, in a label‐free manner.

Characterization of the distribution of rotational torque on electrorotation chips with 3D electrodes

This is a study of in‐plane and out‐of‐plane distribution of rotational torque (ROT‐T) and effective electric field (EEF) on electrorotation (ER) devices with 3D electrodes using finite element modeling (FEM) and experimental method. The objective of this study is to investigate electrical characteristics of the ER devices with five different electrode geometries and obtain an optimum structure for ER experiments. Further, it provides a comparison between characteristics of the 3D electrodes and traditionally used 2D electrodes. 3D distributions of EEF were studied by the time‐variant FEM. FEM results were verified experimentally by studying the rotation of biological cells. The results show that the variations of ROT‐T and EEF over the measurement area of the devices are considerably large. This can potentially lead to misinterpretation of recorded data. Therefore, it is essential to specify the boundaries of the measurement area with minimum deviation from the central EEF. For this purpose, FE analyses were utilized to specify the optimal region. Thereby, with confining the measurements to these regions, the dependency of ROT‐T on the spatial position of the particles can be eliminated. Comparisons have been made on the sustainability of the EEF and ROT‐T distributions for each device, to find an optimum design. Analyses of the devices prove that utilization of the 3D electrodes eliminate irregularities of EEF and ROT‐T along the z‐axis. The Results show that triangular electrodes provide the highest sustainability for the in‐plane ROT‐T and EEF distribution, while the oblate elliptical and circular electrodes have the lowest variances along the z‐axis.

Hybrid Energy Harvester Using Piezoelectric and Pyroelectric Properties of PZT-5A Ceramics

This paper presents a novel hybrid piezoelectric-pyroelectric energy harvester using a cantilever beam with a PZT tip mass. The cantilever is moving between two surfaces with different temperatures under external vibration. PZT ceramic is used as the piezoelectric material, which also has pyroelectric characteristics. By using the pyroelectric effect along with the piezoelectric one, the output RMS voltage of the PZT ceramic was enhanced up to 10% under 50°C ΔT.

An electrostatic parylene microvalve for lab-on-a-chip applications

This paper presents a novel electrostatically actuated microvalve for lab-on-a-chip applications, fabricated using surface micromachining techniques. Lab-on-a-chip applications generally involve in-plane microflows. Microvalve mentioned here operates by moving a diaphragm, which is in-plane with the flow, perpendicular to the stream with the help of electrostatic forces. Operating principles and the operation of the valve are presented in the paper.