Browsing by Author "Solmaz, M. E."
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Item Open Access CO2 laser polishing of microfluidic channels fabricated by femtosecond laser assisted carving(Institute of Physics Publishing, 2016-10) Serhatlioglu, M.; Ortaç, B.; Elbuken, C.; Bıyıklı, Necmi; Solmaz, M. E.In this study, we investigate the effects of CO2 laser polishing on microscopic structures fabricated by femtosecond laser assisted carving (FLAC). FLAC is the peripheral laser irradiation of 2.5D structures suitable for low repetition rate lasers and is first used to define the microwell structures in fused silica followed by chemical etching. Subsequently, the bottom surface of patterned microwells is irradiated with a pulsed CO2 laser. The surfaces were characterized using an atomic force microscope (AFM) and scanning electron microscope (SEM) in terms of roughness and high quality optical imaging before and after the CO2 laser treatment. The AFM measurements show that the surface roughness improves more than threefold after CO2 laser polishing, which promises good channel quality for applications that require optical imaging. In order to demonstrate the ability of this method to produce low surface roughness systems, we have fabricated a microfluidic channel. The channel is filled with polystyrene bead-laden fluid and imaged with transmission mode microscopy. The high quality optical images prove CO2 laser processing as a practical method to reduce the surface roughness of microfluidic channels fabricated by femtosecond laser irradiation. We further compared the traditional and laser-based glass micromachining approaches, which includes FLAC followed by the CO2 polishing technique.Item Open Access Integration of glass micropipettes with a 3D printed aligner for microfluidic flow cytometer(Elsevier B.V., 2018) Bayram, A.; Serhatlıoğlu, Murat; Ortaç, Bülend; Demic, S.; Elbüken, Çağlar; Sen, M.; Solmaz, M. E.In this study, a facile strategy for fabricating a microfluidic flow cytometer using two glass micropipettes with different sizes and a 3D printed millifluidic aligner was presented. Particle confinement was achieved by hydrodynamic focusing using a single sample and sheath flow. Device performance was extracted using the forward and side-scattered optical signals obtained using fiber-coupled laser and photodetectors. The 3-D printing assisted glass capillary microfluidic device is ultra-low-cost, not labor-intensive and takes less than 10 min to fabricate. The present device offers a great alternative to conventional benchtop flow cytometers in terms of optofluidic configuration.Item Open Access Microfluidic bio-particle manipulation for biotechnology(Elsevier, 2014) Çetin B.; Özer, M. B.; Solmaz, M. E.Microfluidics and lab-on-a-chip technology offers unique advantages for the next generation devices for diagnostic therapeutic applications. For chemical, biological and biomedical analysis in microfluidic systems, there are some fundamental operations such as separation, focusing, filtering, concentration, trapping, detection, sorting, counting, washing, lysis of bio-particles, and PCR-like reactions. The combination of these operations led to the complete analysis systems for specific applications. Manipulation of the bio-particles is the key ingredient for these applications. Therefore, microfluidic bio-particle manipulation has attracted a significant attention from the academic community. Considering the size of the bio-particles and the throughput of the practical applications, manipulation of the bio-particles is a challenging problem. Different techniques are available for the manipulation of bio-particles in microfluidic systems. In this review, some of the techniques for the manipulation of bio-particles; namely hydrodynamic based, electrokinetic-based, acoustic-based, magnetic-based and optical-based methods have been discussed. The comparison of different techniques and the recent applications regarding the microfluidic bio-particle manipulation for different biotechnology applications are presented. Finally, challenges and the future research directions for microfluidic bio-particle manipulation are addressed. © 2014 Elsevier B.V.Item Open Access Perfectly absorbing ultra thin interference coatings for hydrogen sensing(OSA - The Optical Society, 2016) Serhatlioglu, M.; Ayas S.; Bıyıklı, Necmi; Dana, A.; Solmaz, M. E.Here we numerically demonstrate a straightforward method for optical detection of hydrogen gas by means of absorption reduction and colorimetric indication. A perfectly absorbing metal-insulator-metal (MIM) thin film interference structure is constructed using a silver metal back reflector, silicon dioxide insulator, and palladium as the upper metal layer and hydrogen catalyst. The thickness of silicon dioxide allows the maximizing of the electric field intensity at the Air/SiO2 interface at the quarter wavelengths and enabling perfect absorption with the help of highly absorptive palladium thin film (∼7 nm). While the exposure of the MIM structure to H2 moderately increases reflection, the relative intensity contrast due to formation of metal hydride is extensive. By modifying the insulator film thickness and hence the spectral absorption, the color is tuned and eye-visible results are obtained.Item Open Access Sheathless microflow cytometry using viscoelastic fluids(Nature Publishing Group, 2017) Asghari, M.; Serhatlioglu, M.; Ortaç, B.; Solmaz, M. E.; Elbuken, C.Microflow cytometry is a powerful technique for characterization of particles suspended in a solution. In this work, we present a microflow cytometer based on viscoelastic focusing. 3D single-line focusing of microparticles was achieved in a straight capillary using viscoelastic focusing which alleviated the need for sheath flow or any other actuation mechanism. Optical detection was performed by fiber coupled light source and photodetectors. Using this system, we present the detection of microparticles suspended in three different viscoelastic solutions. The rheological properties of the solutions were measured and used to assess the focusing performance both analytically and numerically. The results were verified experimentally, and it has been shown that polyethlyene oxide (PEO) and hyaluronic acid (HA) based sheathless microflow cytometer demonstrates similar performance to state-of-the art flow cytometers. The sheathless microflow cytometer was shown to present 780 particles/s throughput and 5.8% CV for the forward scatter signal for HA-based focusing. The presented system is composed of a single capillary to accommodate the fluid and optical fibers to couple the light to the fluid of interest. Thanks to its simplicity, the system has the potential to widen the applicability of microflow cytometers.Item Open Access Tunable ring-coupled Mach-Zehnder interferometer based on lithium niobate(Taylor and Francis, 2014) Solmaz, M. E.The fabrication and characterization are reported of a Fano resonance-based electro-optically tunable ring resonator-coupled Mach-Zehnder interferometer device based on a chalcogenide-lithium niobate hybrid waveguide system. The experiments reveal inherent asymmetric lineshapes that can be flipped to a near symmetrical resonance by applying a dc voltage of ~10 V across the electrode at the MZI non-resonator arm. Further increase in voltage yields the reverse of initial asymmetry. The optical filter-based transfer-matrix model easily explains the experimental data and indicates ways to further enhance the usability of such architecture. © 2014 Taylor and Francis.