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Öğe 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 GuneriMagneto-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.Öğe Development electrically conductive PAAm/Alg/CNC/rGO/PANI hydrogel composites and investigation their bioelectronic properties(Elsevier, 2023) Oruc, Sedat; Boztepe, Cihangir; Zengin, ReyhanCharacterizing 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.Öğe Development of breast tissue-mimicking electrical and acoustic phantoms for magneto-acoustic electrical tomography(Wiley, 2025) Zengin, Reyhan; Gencer, Nevzat GueneriMagneto-acousto electrical tomography (MAET) is a novel medical imaging technique that relies on the difference in electrical properties between healthy and tumor tissues. To facilitate MAET experiments, this study proposes a comprehensive procedure for developing, characterizing, and preserving realistic breast tissue-mimicking phantoms. We developed nontoxic and inexpensive phantoms using sodium alginate, graphite powder, agar, propanediol, aluminum powder, glycine, and deionized water. The dielectric (conductivity and permittivity) and acoustic (speed of sound) properties of phantoms (breast fat, breast gland, and tumor) within the 1-8 MHz frequency range were measured to ensure their suitability for MAET experiments. In conclusion, this study presents a detailed methodology for the preparation, characterization, and preservation of realistic breast tissue-mimicking phantoms tailored for MAET experiments.Öğe Development of Dual-Functional Hydrogel-Based Conductive Electrodes for Accelerated Wound Healing and Motion Sensing(Wiley-V C H Verlag Gmbh, 2025) Boztepe, Cihangir; Bulucu, Firat Orhan; Zengin, ReyhanFlexible conductive hydrogel-based electrodes are promising for biomedical use, combining enhanced wound healing, bioelectrical signaling, and real-time motion sensing, with broad potential in personalized medicine, wearable electronics, and smart prosthetics. In this study, electrically conductive hydrogels with dual functionality were developed for accelerated wound healing and motion sensing applications. The hydrogel electrodes were synthesized via a freeze-thaw cross-linking method using polyvinyl alcohol (PVA), crystalline nanocellulose (CNC), Laponite (LAP), and polyaniline (PANI). The influence of CNC and LAP content on the electrical conductivity, mechanical strength, swelling capacity, and degradation behavior of the hydrogels was systematically investigated. The PVA-CNC-LAP/PANI hydrogel optimized for electrical conductivity (1.5 wt.% CNC and 1.25 wt.% LAP) demonstrated outstanding multifunctional performance, combining robust mechanical strength (490 kPa tensile strength, 2.57 mm/mm elongation, 162 kPa elastic modulus, and 656 kJ/m(3) toughness) with excellent electrical properties, including high conductivity (33.65 S/m), reliable sensitivity (gauge factor = 1.74), and remarkable durability (>500 cycles at 20% strain). Biocompatibility and cell migration potential of this hydrogel electrode were assessed through scratch assays using human dermal fibroblasts (HDF). Additionally, the hydrogel's performance was evaluated in flexible sensor, smart finger actuator, and electrocardiogram (ECG) electrode applications. The biocompatible PVA/CNC/PANI-LAP hydrogel electrodes exhibited satisfactory electrical conductivity, excellent mechanical integrity, and electroresponsive behavior, thereby effectively supporting HDF proliferation, directed migration, and motion detection capabilities.Öğe Numerical Analysis of Spinal Cord Stimulation with an Eight-Shape Electrode Model(Ieee, 2022) Aydin, Elif Feyza; Zengin, ReyhanSpinal 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.Öğe Static Magnetic Field Focusing With Neodymium Magnets For Wound Healing: A Numerical Study(2024) Zengin, Reyhan; Aydın, Elif FeyzaStatic magnetic fields (SMFs) find widespread applications in diverse scientific, technological, and medical domains. This study explores the potential of neodymium permanent magnets in focusing and controlling SMFs, specifically emphasizing wound healing applications. Numerical simulations using COMSOL Multiphysics create a uniform static magnetic field for wound healing. The study systematically increases the number of neodymium magnets, demonstrating enhanced magnetic flux density and a focused magnetic field. The results affirm the efficacy of neodymium magnets in generating a uniform static magnetic field between 160-600 m Tesla. This research proposes neodymium permanent magnets as a promising tool for wound healing applications, offering a non-invasive and focused therapeutic approach. While the study provides valuable insights, further experimental and clinical validations are necessary to establish the real-world efficacy of this method. The work contributes to the evolving understanding of static magnetic fields as a viable therapeutic modality for various medical conditions, particularly in the context of wound healing.
