Browsing by Author "Kasirga, T. S."
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Item Open Access Microfluidics for reconfigurable electromagnetic metamaterials(AIP Publishing, 2009) Kasirga, T. S.; Ertas, Y. N.; Bayındır, MehmetWe propose microfluidics as a useful platform for reconfigurable electromagnetic metamaterials. Microfluidic split-ring resonators (MF-SRRs) are fabricated inside a flexible elastomeric material by employing rapid prototyping. The transmission measurements performed for mercury-injected MF-SRR exhibits sharp magnetic resonances at microwave wavelengths. We further calculate transmission properties of the MF-SRR array and the effect of electrical conductivity of the liquid inside the channel on the magnetic resonance. The measured results agree well with numerical calculations. Our proposal may open up directions toward switchable metamaterials and reconfigurable devices such as filters, switches, and resonators.Item Open Access Visualization of one-dimensional diffusion and spontaneous segregation of hydrogen in single crystals of VO2(Institute of Physics Publishing, 2016-07) Kasirga, T. S.; Coy, J. M.; Park, J. H.; Cobden, D. H.Hydrogen intercalation in solids is common, complicated, and very difficult to monitor. In a new approach to the problem, we have studied the profile of hydrogen diffusion in single-crystal nanobeams and plates of VO2, exploiting the fact that hydrogen doping in this material leads to visible darkening near room temperature connected with the metal-insulator transition at 65 �C. We observe hydrogen diffusion along the rutile c-axis but not perpendicular to it, making this a highly one-dimensional diffusion system. We obtain an activated diffusion coefficient ∼ 0.01 e-0.6eV/kBT cm2s-1, applicable in metallic phase. In addition, we observe dramatic supercooling of the hydrogen-induced metallic phase and spontaneous segregation of the hydrogen into stripes implying that the diffusion process is highly nonlinear, even in the absence of defects. Similar complications may occur in hydrogen motion in other materials but are not revealed by conventional measurement techniques.