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Öğe A simple approach for the fabrication of 3D microelectrodes for impedimetric sensing(IOP PUBLISHING, 2015) Güler, Mustafa Tahsin; Bilican, İsmail; A?an, Sedat; Elbüken, ÇağlarIn this paper, we present a very simple method to fabricate three-dimensional (3D) microelectrodes integrated with microfluidic devices. We form the electrodes by etching a microwire placed across a microchannel. For precise control of the electrode spacing, we employ a hydrodynamic focusing microfluidic device and control the width of the etching solution stream. The focused widths of the etchant solution and the etching time determine the gap formed between the electrodes. Using the same microfluidic device, we can fabricate integrated 3D electrodes with different electrode gaps. We have demonstrated the functionality of these electrodes using an impedimetric particle counting setup. Using 3D microelectrodes with a diameter of 25 mu m, we have detected 6 mu m-diameter polystyrene beads in a buffer solution as well as erythrocytes in a PBS solution. We study the effect of electrode spacing on the signal-to-noise ratio of the impedance signal and we demonstrate that the smaller the electrode spacing the higher the signal obtained from a single microparticle. The sample stream is introduced to the system using the same hydrodynamic focusing device, which ensures the alignment of the sample in between the electrodes. Utilising a 3D hydrodynamic focusing approach, we force all the particles to go through the sensing region of the electrodes. This fabrication scheme not only provides a very low-cost and easy method for rapid prototyping, but which can also be used for applications requiring 3D electric field focused through a narrow section of the microchannel.Öğe Alternative screening method for analyzing the water samples through an electrical microfluidics chip with classical microbiological assay comparison of P. aeruginosa(Elsevier B.V., 2020) Bilican, İsmail; Bahadır, Tolga; Bilgin, Kemal; Güler, Mustafa TahsinPseudomonas aeruginosa is a pathogenic bacterium in fresh water supplies that creates a risk for public health. Microbiological analysis of drinking water samples is time consuming and requires qualified personnel. Here we offer a screening system for rapid analysis of spring water that has the potential to be turned into a point-of-need system by means of simple mechanism. The test, which takes 1 h to complete, electrically interrogates the particles through a microfluidic chip suspended in the water sample. We tested the platform using water samples with micro beads and water samples spiked with P. aeruginosa at various concentrations. The mono disperse micro beads were used to evaluate the performance of the system. The results were verified by the gold standard membrane filtration method, which yielded a positive test result only for the P. aeruginosa spiked samples. Detection of 0–11 k bacteria in 30 ?L samples was successfully completed in 1 h and compared with a conventional microbiological method. The presented method is a good candidate for a rapid, on-site, screening test that can result in a significant reduction in cost and analysis time compared to microbiological analyses routinely used in practice.Öğe An in-situ fabrication technique to form integrated microelectrodes(Chemical and Biological Microsystems Society, 2015) Güler, Mustafa Tahsin; Bilican, İsmail; Işıksaçan, Ziya; A?an, Sedat; Elbüken, ÇağlarIn this study we have developed a new fabrication method to form microelectrodes for microfluidic applications. We present a microfabrication route to achieve embedded microelectrodes within a microchannel without needing for a microfabrication facility or lithography and metallization processes. This method includes attaching a gold microwires on a glass slide and bonding PDMS micro channels perpendicular to the microwire. Then aqua regia solution is passed through the channel etching the wire inside of the channel and forming two electrodes on the two sides. We applied these electrodes to the impedance flow cytometry for high sensitive detection of polystyrene beads and red blood cells. We also compared the performance of our electrodes with the coplanar electrodes which is the most commonly used geometry of the impedance flow cytometry. The etched electrodes give up to 20 times better SNR compared to coplanar electrodes. © 15CBMS-0001.Öğe Applicability of innovative adsorbents in geogenic arsenic removal(Elsevier Ltd, 2021) Çelebi, Hakan; Bilican, İsmail; Bahadır, TolgaExposure to high concentrations of geogenic arsenic via well-waters is a worldwide health concern. The purpose of the present work was to search the experimental results of the behavior of raw Uspheres (RU), iron Uspheres (FeU), iron Uspheres 200 °C (FeU@200°C) in the removal of arsenic in accordance with some factors impacting the adsorption process. Some study parameters including initial pH (2–10), adsorbent amount (0.1–10.0 g), temperature (10–50 °C), and operating time (5–90 min) were examined. Under wanted conditions, maximum removal efficiencies of 90.36%, 98.04%, and 97.86% were obtained with RU, FeU, and FeU@200°C, respectively. The equilibrium adsorption was found to match the Langmuir isotherm model based on the collected data. The maximum adsorption capacity of RU, FeU, and FeU@200°C was 6.09, 6.61, and 6.46 mg/g, severally. The arsenic adsorption onto RU, FeU, and FeU@200°C was acknowledged by the pseudo-second-order. Electrostatic interaction and surface complexation mechanisms are involved in arsenic adsorption. The Box-Behnken statistical experiment design method was applied to specify the impact of pH, temperature, and the amount of RU, FeU, and FeU@200°C on the percentage of arsenic removal.Öğe Assessment of PMMA and polystyrene based microfluidic chips fabricated using CO2 laser machining(Elsevier B.V., 2020) Bilican, İsmail; Güler, Mustafa TahsinLaser machining could be an alternative way for the fabrication of microchannels. In this study, laser machining of polymethylmethacrylate (PMMA) and polystyrene (PS) substrates were characterized in detail. A fabrication method preventing leakage at PS microchannel inlets was developed. The effect of laser parameters (power, speed and frequency) on engraving was analyzed by scanning electron microscopy. Laser ablation mechanism of both materials was explained through thermal analysis and material properties. Defocusing the laser beam was also analyzed as an additional parameter affecting the channel profile. Two parameters affecting the resolution were analyzed which are the minimum channel size that can be achieved by the laser beam and x-y stage of the laser engraver for straight and complex microchannel geometries. The hydrophilicity of the surface before and after laser machining was tested with contact angle measurements. The capabilities/limitations of machining were revealed through some complex channel structures. Finally, a passive micromixer and a droplet generator microfluidic devices were manufactured and tested, and promising results were obtained.Öğe Capacitive detection of single bacterium from drinking water with a detailed investigation of electrical flow cytometry(Elsevier Science Sa, 2018) Güler, Mustafa Tahsin; Bilican, İsmailPathogenic contamination of drinking water is critical in regard to human health. In this study, we investigated the electrical detection of single bacterium from drinking water. A microfluidics chip consisting of polydimethylsiloxane (PDMS) microchannel and gold microelectrodes was fabricated with conventional microfabrication techniques. Electrical characterizations were done with an LCR meter and the measurements were in good agreement with simulation results. The impact of channel and electrode dimensions was studied for the different type and size of particles, using both experimental and simulation techniques. In addition, the effect of excitation signal frequency and solution conductivity was analyzed employing both simulation and experimental methods. Finally, capacitive detection of a single Escherichia coli (E. coli) from drinking water was successfully carried out under optimum parameters and design geometries.Öğe Capacitive solvent sensing with interdigitated microelectrodes(SPRINGER, 2016) Bilican, İsmail; Güler, Mustafa Tahsin; Gülener, Neşet; Yüksel, Mustafa; Ağan, SedatWe were able to quantify dielectric properties of solvents such as DI water, isopropyl alcohol, and acetone using interdigitated microelectrodes (IMEs). IMEs were fabricated using conventional micro fabrication techniques. The fabricated IMEs were dipped into the solution, and the dielectric property of the medium was measured. A range of frequencies and excitation voltages were swept in order to determine the operation region that yields the highest signal to noise ratio. Measurements were performed at 1 MHz and 100 mV which resulted in best signal to noise ratio. We applied a simple analytical model for the calculation of the capacitance and measured the capacitance value using a simple parallel capacitor and resistor model which resulted in perfect agreement with theoretical results. The presented sensor provides a simple and accurate method to determine solvent type which may have possible future applications.Öğe Capacitive solvent sensing with microfluidics chip(Süleyman Demirel Üniversitesi, 2018) Bilican, İsmail; Güler, Mustafa TahsinSolvents are widely used in daily life as well as in almost all laboratories. Identification and detection of these solvents used in many areas have great importance in terms of health, toxicology and environment. For this reason, the main purpose of our study is to be able to identify the solvents in practical ways. In this study, gold microelectrodes were used to define the capacitance detection of various solvents in the frequency range of 20 kHz - 2 MHz. Moreover, the electrical noise and signal output of the solvents at different frequencies were investigated. Measurements were made by micro-channels integrated on microelectrodes for reducing noises and detection with high sensibility.Öğe Cascaded contraction-expansion channels for bacteria separation from RBCs using viscoelastic microfluidics(Elsevier, 2021) Bilican, İsmailImplementation of viscoelasticity-based particle migration techniques has attracted significant interest thanks to its simplicity to achieve particle separation and enrichment at high sensitivity and accuracy for the last decade. Many methods have previously been developed for particle focusing and separation, but they all require long fluidic channels to enable the desired elastic force on particles. Here, a cascade contraction-expansion microfluidic system with a much shorter channel length is presented. Experimental results show that this system achieved continuous, sheathless particle separation in a viscoelastic fluid, and Enterococcus faecalis was successfully separated from red blood cells (RBCs). Thanks to its small size, the system provides extra advantage for its integration into small chips. (c) 2021 Elsevier B.V. All rights reserved.Öğe Chitosan loses innate beneficial properties after being dissolved in acetic acid: Supported by detailed molecular modeling(American Chemical Society, 2020) Bilican, İsmail; Pekdemir, Sami; Önses, Mustafa Serdar; Akyüz, Lalehan; Altuner, Ergin Murat; Koç Bilican, Behlül; Zang, Liansheng; Mujtaba, Muhammad; Muler?ikas, Povilas; Kaya, MuratChitosan, which is obtained via deacetylation of chitin, has a variety of uses in agriculture, food, medicine, pharmaceuticals, and cosmetics. Industrial chitosan is in a gel form, which is produced by dissolving in acetic acids. These gels can be chitosan-only films or composite films that include other ingredients such as plant extracts or other polymers. Chitosan-based films, however, are not as natural as chitosan dissolved in weak acids, and they lack some of chitosan's innate properties. In this study, natural chitosan films (NCFs) were obtained from the pupa shells of black soldier flies through a process that maintains the original structure. The semisynthetic film (SCF) was then produced by dissolving the same NCF in acetic acid along with glycerol and glutaraldehyde. The semisynthetic film remarkably lost the beneficial properties of the natural film. The deteriorated characteristics include hydrophobicity, crystallinity, thermal properties, as well as a loss of fibril structure and a reduction in bacterial attachment. Moreover, the Ag-deposited NCFs manifested strikingly higher surface-enhanced Raman scattering activity as compared with the semisynthetic ones. These results, including the molecular modeling data, demonstrate that dissolving chitosan in acetic acid changes its polymeric structure. © 2020 American Chemical Society.Öğe CO2 laser machining for microfluidics mold fabrication from PMMA with applications on viscoelastic focusing, electrospun nanofiber production, and droplet generation(Korean Society of Industrial Engineering Chemistry, 2021) Güler, Mustafa Tahsin; İnal, Murat; Bilican, İsmailIn this study, a new method for the fabrication of polydimethylsiloxane (PDMS) microchannels through the replication of plexiglass molds was developed. A plexiglass slab is machined with CO2 laser in the raster mode to produce the mold for the PDMS casting. Then, the PDMS replica of the mold is plasma bonded to a substrate by applying more pressure than standard to overcome the surface roughness inherited from the laser machining process. Depending on the channel complexity, a ready to cast mold in the size of a glass slide can be achieved in 5–20 min, including the design, machining, and cleaning steps. This fully automated and cost-effective mold making method proved to be the fastest among all methods, and it enables up to 2.5 aspect ratio microchannels, down to a width of 60 ?m, and a height of 23 ?m. The raster mode of the laser provides features lower, in size, then the laser beam waist radius. The produced microchannels were validated using several applications, such as droplet generation, nanofiber production, and viscoelastic microparticle focusing.Öğe Focusing-free impedimetric differentiation of red blood cells and leukemia cells: A system optimization(Elsevier B.V., 2020) Bilican, İsmail; Güler, Mustafa Tahsin; Serhatlıoğlu, Murat; Kırındı, Talip; Elbüken, ÇağlarA focusing-free microfluidic impedimetric cell detection system is developed. The effect of the channel dimensions, solution conductivity, excitation voltage, and particle size on impedimetric signal outputs were optimized to increase the sensitivity of the system. Conventional microfabrication techniques were adapted to obtain low height, resealable microchannels. The geometry optimization was performed by a combination of analytical, numerical and experimental approaches. The results demonstrate that reliable impedimetric particle differentiation can be achieved without any labeling or particle focusing. The system parameters were studied and rule-of-thumb design criteria were provided. Finally, using the developed system, red blood cells and leukemia cells were experimentally detected and differentiated. Thanks to its simplicity, the focusing-free cell differentiation system may find applications in several cellular diagnostic uses.Öğe From bio-waste to biomaterials: The eggshells of Chinese oak silkworm as templates for SERS-active surfaces(Elsevier B.V., 2021) Zang, Lian-Sheng; Chen, Yong-Ming; Koç Bilican, Behlül; Bilican, İsmail; Şakir, Menekşe; Wait, James; Çolak, Arzu; Karaduman, Tuğçe; Ceylan, Ahmet; Ali, Asad; Elbuken, Çağlar; Önses, M. Serdar; Kaya, MuratAlthough over 80% of the world's existing animal species are insects, with each of these species having unique eggshell morphologies, limited information is available regarding the use of their eggshells in material science applications. The present research discusses using discarded eggshells of the Chinese oak silkworm (Antheraea pernyi) as a technological material. The 3-dimensional aspects of the insect's eggshell were examined in detail, demonstrating the complexity of their novel surface morphology. The outer surface of the eggshell was comprised of a hexagonal structure, whereas the inner surface consists of a mostly smooth surface. Distinctive layers of the eggshell were observed when cross sections of the surface were analyzed. The elastic modulus of the inner part of the eggshell is substantially greater than that of the outer part. The physicochemical properties of the eggshell were characterized and no toxic properties were found. The hexagonal structures found on the outer surface of the eggshell provide a highly suitable template for silver nanostructure deposition. The resulting silver decorated surfaces can be used to detect molecules via surface-enhanced Raman scattering (SERS) effects. The deposition of silver renders the surface antimicrobial, whereas the original surface was microbial. Collectively, the insights gained in this study will be key in developing advanced engineering applications of the insect eggshells.Öğe Fıstık kabuğu ile sulardan metilen mavisi gideriminin atık yönetimi yaklaşımıyla incelenmesi(Uludağ Üniversitesi, 2024) Çelebi, Hakan; Tulun, Şevket; Şimşek, İsmail; Bahadır, Tolga; Bilican, İsmailBoyar maddelerin kullanımının yaygınlaşması, özellikle tekstil endüstrisinin gelişmesi su kirliliğinin en önemli nedenlerinden bir olan boya kirliliğini oluşturmaktadır. Günümüzde metilen mavisi (MM), tekstil endüstrisinde yaygın olarak kullanılan boyar maddedir. Bu çalışmada, atık olarak kabul edilen ham yer fıstığı kabuğunun (YFK) adsorbent olarak kullanılarak metilen mavisinin (MM) giderim şartları incelenmiştir. Herhangi bir işlem yapılmadan alınan YFK adsorbentinin farklı dozlarda (0,1, 0,5, 1, 2, 3, 5 g), işletme sürelerinde (5, 10, 15, 30, 45, 60, 90, 120, 150 dk), pH değerlerinde (2, 4, 6, 8, 10, 12) ve sıcaklıklarında (20, 25, 30, 35, 40 °C) giderim verimine etkileri araştırılmıştır. Yapılan çalışmalarda, en uygun adsorpsiyon şartları: YFK miktarı 0,5 g, işletme süresi 15 dakika, pH 4, sıcaklık 20 °C olarak bulunmuştur. İzoterm modellerinin korelasyon değerleri incelendiğinde en yüksek korelasyon değeri Langmuir izotermine (R2=0,9999) olduğu belirlenmiştir. Gerçekleşen adsorpsiyon mekanizması YFK’nın yüzeyinde tek bir tabaka halinde MM tutulduğu sonucuna varılmıştır. Herhangi bir işlem yapılmadan kullanılan YFK’nın yeşil atık yönetimi yaklaşımı ile boyar madde giderimi için uygun bir adsorbent olarak kullanılabileceği belirlenmiştir.Öğe Macroporous surgical mesh from a natural cocoon composite(American Chemical Society, 2022) Chen, Yong-Ming; Zang, Lian-Sheng; Koç-Bilican, Behlül; Bilican, İsmail; Holland, Chris; Cansaran-Duman, Demet; Karaduman, Tuğçe; Çolak, ArzuRecently, traditional polymer-based surgical meshes have drawn unwanted attention as a result of host tissue complications arising from infection, biocompatibility, and mechanical compatibility. Seeking an alternative solution, we present a hierarchically structured nanofibrous surgical mesh derived from the naturally woven cocoon of the Japanese giant silkworm, termed MothMesh. We report that it displays nontoxicity, biocompatibility, suitable mechanical properties, and porosity while showing no adverse effect in animal trials and even appears to enhance cell proliferation. Hence, we assert that the use of this natural material may provide an effective and improved alternative to existing synthetic meshes.Öğe Natural ?-chitin-protein complex film obtained from waste razor shells for transdermal capsaicin carrier(Elsevier B.V., 2020) Aylanç, Volkan; Ertosun, Şeymanur; Akyüz, Lalehan; Koç Bilican, Behlül; Gökdağ, Semih; Bilican, İsmail; Çakmak, Yavuz Selim; Akyüz Yılmaz, Bahar; Kaya, MuratIn the literature, the produced ?-chitin samples are in powder or flake forms but there is no natural ?-chitin based film. Also, the commercially available transdermal patches are produced from synthetic polymers. In this regard, we produced natural ?-chitin-protein complex (CPC) film from the waste shells of Ensis spp. The obtained natural film was characterized by FTIR, TGA and SEM. Additionally, swelling, thickness, contact angle and antioxidant tests were done to learn more about the films. After production and characterization of the film, capsaicin, which is commonly used for pain relief was loaded into the film. The loading capacity was recorded as 5.79%. The kinetic models were studied in three different pH, then the results were fitted with Higuchi model with high correlation at pH 7.4. After considering all the obtained results, the capsaicin loaded CPC film may be an alternative candidate for transdermal patch instead of the synthetic ones.Öğe Numerical thickness optimization study of CIGS based solar cells with wxAMPS(Elsevier GmbH, 2016) Yasar, S.; Kahraman, S.; Cetinkaya, S.; Apaydin, S.; Bilican, İsmail; Uluer, I.In this paper, a numerical investigation of the effects of thickness of absorber and buffer layers for a typical CIGS based solar cell was carried out for the first time, employing the wxAMPS software which is a new custom-designed software package for solar cell simulation. We have examined how the output parameters change with absorber and buffer thicknesses and suggested four different cell structures. By using the baseline structure, an optimum band gap value of 1.4 eV was determined for the CIGS absorber layer prior to do thickness study. Optimum absorber thickness value has been determined as 2500 nm from the simulation results. Spectral response of the cell decreased with increasing thickness in blue region. The influence of buffer layer thickness was investigated and it was found that most of the photo-generated carriers are collected by a thinner CdS layer. A significant decrease in current density, open circuit voltage and conversion efficiency occurred with increasing buffer layer thickness. This behavior was attributed to a decrease in the number of collected carriers due to the recombination of electron-hole pairs proceeded from the absorbed photons in the CdS bulk for large thickness. As a result, efficiencies around 27% were obtained through optimization while that of baseline structure was 25%. Our results have shown that the suggested structures both produce higher efficiencies than that of baseline structure and may lead to produce more efficient CIGS-based thin film solar cells. (C) 2016 Elsevier GmbH. All rights reserved.Öğe Polyethylene glycol-assisted growth of Cu2SnS3 promising absorbers for thin film solar cell applications(Taylor & Francis, 2014) Kahraman, Süleyman; Çetinkaya, Samed; Yaşar, Soner; Bilican, İsmailIn this paper, we report, for the first time, the results of the polyethylene glycol- (PEG) assisted preparation and characterization of high-quality and well-crystallized Cu2SnS3 (CTS) thin films obtained using sol-gel spin-coating method and a subsequent annealing in a sulphur atmosphere. Structural, morphological, compositional, electrical and optical investigations were carried out. The X-ray diffraction patterns of the samples proved the polycrystalline nature and preferred crystallization of the films. No peak referring to other binary or ternary phases were detected in the patterns. The intensity of the preferred orientation and crystallite size of the films increased with increasing PEG content. This trend yielded an improvement in photo-transient currents of the PEG-assisted growth of CTS films. The scanning electron microscopy images revealed that the CTS films have continuous, dense and agglomeration-like morphology. Through energy dispersive X-ray spectroscopy studies, it has been deduced that the samples consist of Cu, Sn and S of which atomic percentages were consistent with Cu/Sn and S/metal initial ratios. The agglomerated morphology of the samples has been attributed to increasing PEG content. A remarkable enhancement was observed in photo-transient currents of p-n junction of the produced films along with increasing PEG content. Through resistivity-temperature measurements, three impurity level electrical activation energy values for each film were found. Optical band gap values of the films were estimated via absorbance-wavelength behaviours and decreased with increasing PEG content. It has been revealed that PEG-assisted growth of CTS thin films is a promising way to improve its photovoltaic characteristics.Öğe Preparation and Properties of Novel Mucilage Composite Films Reinforced with Polydimethylsiloxane(Wiley-VCH, 2024) Bilican, İsmailRecently, there is an increasing interest in research on biodegradable, non-toxic, and high-strength biomaterials that can replace plastics, especially in the food industry. In this study, mucilage obtained from Linum usitatissimum seeds is used to develop a natural biodegradable biomaterial by reinforcing it with different concentrations of polydimethylsiloxane (PDMS). The biomaterials produced in the form of films are thoroughly investigated in terms of physicochemical (Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDX), atomic force microscopy (AFM), contact angle, and mechanical), biodegradable (in soil and water), and antibacterial properties. SEM-EDX and AFM demonstrate the homogeneous distribution of PDMS throughout the mucilage matrix. The incorporation of PDMS improves the water solubility of the mucilage composite films, thereby enhancing their strength. It also imparts hydrophobic characteristics to the composite films. Thus, PDMS ensures the high barrier property of the composite films against water vapor. Furthermore, the addition of PDMS increases the antimicrobial properties of the mucilage composite films. The obtained results indicate that the first-time produced mucilage-PDMS composite films can serve as an alternative product for food packaging applications.Öğe Production of natural chitin film from pupal shell of moth: Fabrication of plasmonic surfaces for SERS-based sensing applications(Elsevier Ltd, 2021) Chen, Yong-Ming; Pekdemir, Sami; Bilican, İsmail; Koç Bilican, Behlül; Çakmak, Betül; Ali, Asad; Zang, Lian-Sheng; Önses, M. Serdar; Kaya, MuratCommercially available types of chitin or chitin isolate are usually in powder form and are nanofibrous in microstructure. However, the surface characteristics of natural chitin in the body of insects are currently understudied. Herein, natural chitin film was successfully produced from bio-waste of insect pupae of the Japanese giant silkworm. Two different surface morphologies of the chitin film were observed. We report for the first time a micropapillary surface structure of chitin which was observed on the dorsal side of the film. To further potential of the micropapillary structured natural chitin in sensing applications, we develop a protocol for generating a nanoscopic film of Ag using thermal evaporation. The Ag-deposited natural chitin films exhibited surface-enhanced Raman scattering (SERS) activity to an extent depending on the structure of the film. In conclusion, materials science has been expanded by addition of a natural, three-dimensional chitin film with utilizable properties.
