Aziz Koyuncuoglu

This paper presents design and fabrication of a MEMS-based thin film piezoelectric transducer to be placed on an eardrum for fully-implantable cochlear implant (FICI) applications. Resonating at a specific frequency within the hearing band, the transducer senses eardrum vibration and generates the required voltage output for the stimulating circuitry. Moreover, high sensitivity of the sensor, 391.9 mV/Pa @900 Hz, decreases the required power for neural stimulation. The transducer provides highest voltage output in the literature (200 mVpp @100 dB SPL) to our knowledge. A multi-frequency piezoelectric sensor, covering the daily acoustic band, is designed based on the test results and validated through FEA. The implemented system provides mechanical filtering, and mimics the natural operation of the cochlea. Herewith, the proposed sensor overcomes the challenges in FICI operations and demonstrates proof-of-concept for next generation FICIs.

This paper presents the first acoustic experimental results of a MEMS based bulk piezoelectric transducer for use in fully implantable cochlear implants (FICI). For this purpose, the transducer was attached onto an acoustically vibrating membrane. Sensing and energy harvesting performances were measured using neural stimulation and rectifier circuits, respectively. The chip has a 150 Hz bandwidth around 1800 Hz resonance frequency that is suitable for mechanical filtering as a sensor. As an energy harvester, bulk piezoelectric transducer generated a rectified power of 16.25 μW with 2.47 VDC with 120 dB-A sound input at 1780 Hz. Among other MEMS acoustic energy harvesters in the literature, reported transducer has the highest power density (1.5 × 10 −3 W/cm 3) to our knowledge.

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. Three-dimensional 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. This article is protected by copyright. All rights reserved.

Dielectrophoresis (DEP), a technique used to separate particles based on different sizes and/or dielectric properties under non-uniform electric field, is a promising method to be applied in label-free, rapid and effective cell manipulation and separation. In this study, a MEMS-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 crossover frequency of sensitive K562 cells, at which sensi...

ABSTRACT This paper presents the trapping of imatinib resistant K562 (human chronic myelogenic leukemia (CML), K562/IMA) cells with 3D-electrode contactless dielectrophoresis (DEP). 3D electrodes are isolated from the solution by means of uniform thin parylene layer (~0.3μm), to eliminate the Joule heating, electrolysis, and cell damaging. 3D electrodes (extruded along the microchannel in z-axis) provide uniform distribution of DEP force along the channel height, improving the separation efficiency, significantly. It is verified that the system is capable of trapping K562/IMA cells at a concentration of 6.25×105/ml and 10 μl/min flow rate by applying 9 Vpp sinusoidal signal at 48.64 MHz. No trapping occurs for K562 sensitive cells at the same experimental conditions.

This paper presents the design, simulation, and fabrication of a MEMS based dielectrophoresis (DEP) platform for the separation and detection of the human leukemic cancer cells (K562) and its multidrug resistant (MDR) counterpart (K56/IMA-0.2 µM) from the human leukocyte mixture. The pro-posed DEP device, benefits from the 3D isolated electrodes inside a microfluidic channel. 3D elec-trodes (extruded 30 µm in z-direction) were isolated from the medium with thin parylene coating (~ 0.3 µm). In addition, the potentially-floating 3D elec-trodes were utilized to enhance the DEP separation efficiency, for the first time in the literature. These electrodes, elevates the performance of the device by extending the generated electric field gradient inside the DEP separation area. FEM electric field and incompressible Navier-Stoke analyses were utilized to study the separation efficiency of the proposed device. It is shown that under the optimized boundary conditions, the proposed device can ...