Yazar "Zengin, Reyhan" seçeneğine göre listele

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    Data acquisition system for MAET with magnetic field measurements
    (Iop Publishing Ltd, 2019) Kaboutari, Keivan; Tetik, Ahmet Onder; Ghalichi, Elyar; Gozu, Mehmet Soner; Zengin, Reyhan; Gencer, Nevzat Guneri
    Magneto-acousto-electrical tomography (MAET) is an imaging modality to image the electrical conductivity of biological tissues. It is based on electrical current induction by using ultrasound under a static magnetic field. The aim of this study is to develop a data acquisition system for MAET based on magnetic field measurements. The static magnetic field is generated by six permanent neodymium magnets. A 16-element linear phased array (LPA) transducer is utilized to generate acoustic pressure waves inside the phantom. To measure the magnetic field intensity generated by the induced currents, contactless receiver sensors are developed using two similar disk multiple layer coils, which are Helmholtz coil sensor. Physical properties and electrical characteristics of the sensors are assessed. A two-stage cascaded amplifier is designed and utilized in the receiving system. The gain of the cascaded amplifier at 1 MHz is adjusted to be 96 dB. Experimental studies are conducted with two different phantoms, having 3 S m(-1) and 58 S m(-1) electrical conductivity, respectively. A-scan and B-scan images of phantoms are obtained with the LPA transducer. Comparison of the ultrasound (A-scan) and MAET signals reveals that 3 S m(-1) conductive inhomogeneity can be detected with this data acquisition system. Furthermore, the front and rear interfaces of an inhomogeneity (15.15 mm x 30 mm x 20 mm) of 58 S m(-1) conductivity are detectable.
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    Development electrically conductive PAAm/Alg/CNC/rGO/PANI hydrogel composites and investigation their bioelectronic properties
    (Elsevier, 2023) Oruc, Sedat; Boztepe, Cihangir; Zengin, Reyhan
    Characterizing the effects of parameters such as the swelling ratio, composition, and applied current frequency of hydrogels is crucial for the development of flexible, stretchable, and electrically conductive hydrogels that are of importance in a variety of biomedical applications. In this study, poly(Acrylamide) (PAAm), alginate (Alg) and crystalline nanocellulose (CNC) based stretchable PAAm/Alg/CNC/rGO hydrogels containing different amounts of reduced graphene oxide (rGO) in their structure were synthesized. To increase the electrical conductivity of these hydrogels, their composites with polyaniline (PANI) were prepared. The chemical composition and morphological characterizations were performed using FT-IR and SEM analysis techniques. Since the amount of PANI formed in the structure of hydrogel composites was directly proportional to the amount of rGO in the structure, swelling, mechanical and electrical conductivity properties changed depending on the amount of rGO. The swelling ratio and mechanical strength of the PAAm/Alg/CNC/rGO/PANI hydrogel composite series varied between 38 and 50 g water/ g polymer and 76.02-375.95 kPa, respectively. The electrical conductivities of their 25% swollen states at 10-4 MHz ranged from 15.4 to 20.20 S/m. Flex sensor, smart hydrogel fingers and electrocardiogram (ECG) electrode applications were tested. The synthesized hydrogel composite systems were quite successful in these biomedical applications as bioelectronic materials.
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    Numerical Analysis of Spinal Cord Stimulation with an Eight-Shape Electrode Model
    (Ieee, 2022) Aydin, Elif Feyza; Zengin, Reyhan
    Spinal Cord Stimulation is used for drug-free treatment in indications of chronic pain of the spinal cord. As a result of sending current from the electrodes placed in the epidural region of the spinal cord with laminectomy, pain information is prevented from reaching the brain and the patient only feels paresthesia. Today, different shapes of electrode designs are available. In this study, the current density distribution resulting from the application of 0.0417 mA to the anode and -0.0417 mA to the cathode from the eight-shaped electrodes were examined. The maximum current density is 36 mA/cm(2), and this value is within the safety limits that the patient can feel.