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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6

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Now showing 1 - 6 of 6
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    PublicationOpen Access
    Top-down technique for scaling to nano in silicon MEMS
    (American Vacuum Society (AVS), 2017) Wollschlaeger, Nicole; Oesterle, Werner; Leblebici, Yusuf; Department of Mechanical Engineering; Alaca, Burhanettin Erdem; Nadar, Gökhan; Yılmaz, Mustafa Akın; Kılınç, Yasin; Taşdemir, Zuhal; Faculty Member; PhD Student; PhD Student; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; 115108; N/A; N/A; N/A; N/A
    Nanoscale building blocks impart added functionalities to microelectromechanical systems (MEMS). The integration of silicon nanowires with MEMS-based sensors leading to miniaturization with improved sensitivity and higher noise immunity is one example highlighting the advantages of this multiscale approach. The accelerated pace of research in this area gives rise to an urgent need for batch-compatible solutions for scaling to nano. To address this challenge, a monolithic fabrication approach of silicon nanowires with 10-mu m-thick silicon-on-insulator (SOI) MEMS is developed in this work. A two-step Si etching approach is adopted, where the first step creates a shallow surface protrusion and the second step releases it in the form of a nanowire. It is during this second deep etching step that MEMS-with at least a 2-order-of-magnitude scale difference-is formed as well. The technique provides a pathway for preserving the lithographic resolution and transforming it into a very high mechanical precision in the assembly of micro-and nanoscales with an extreme topography. Validation of the success of integration is carried out via in situ actuation of MEMS inside an electron microscope loading the nanowire up to its fracture. The technique yields nanowires on the top surface of MEMS, thereby providing ease of access for the purposes of carrying out surface processes such as doping and contact formation as well as in situ observation. As the first study demonstrating such monolithic integration in thick SOI, the work presents a pathway for scaling down to nano for future MEMS combining multiple scales.
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    PublicationOpen Access
    Droplet resonator based optofluidic microlasers
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2014) Brzobohaty, Oto; Jezek, Jan; Pilat, Zdenek; Zemanek, Pavel; Anand, Suman; McGloin, David; Department of Physics; Kiraz, Alper; Aas, Mehdi; Karadağ, Yasin; Jonas, Alexandr; Faculty Member; PhD Student; Department of Physics; Graduate School of Sciences and Engineering; College of Sciences; 22542; N/A; N/A; N/A
    An SU-8 polymer microdisk resonator coated with a palladium (Pd) layer and coupled to a single-mode optical waveguide is used to as a hydrogen (H-2) gas sensor. In the presence of H2 a red shift is observed in the spectral positions of the microdisk whispering gallery modes (WGMs) due to the expansion in the Pd lattice. H-2 concentrations below the flammable limit (4%) down to 0.3% could be detected in nitrogen atmosphere at room temperature. For H-2 concentrations between 0.3 1%, WGM spectral positions shifted linearly with H-2 concentration at a rate of 32 pm/%H-2. Average response time of the devices was measured to be 50 s for 1% H-2. The proposed device concept can also be used to detect different chemical gases by using appropriate sensing layers.
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    PublicationOpen Access
    Tunable WGM resonators from optically trapped dye doped liquid crystal emulsion droplets
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2014) Sery, Mojmir; Pilat, Zdenek; Jezek, Jan; Zemanek, Pavel; Department of Physics; Department of Electrical and Electronics Engineering; Aas, Mehdi; Kiraz, Alper; Faculty Member; Department of Physics; Department of Electrical and Electronics Engineering; College of Sciences; N/A; 22542
    We have built a complex apparatus for optical trapping, stretching, heating and concurrent whispering gallery mode (WGM) lasing excitation of liquid crystal (LC) emulsion micro-droplets doped with various fluorescent dyes. We have explored the changes of WGM lasing wavelength when the LC droplets were optically stretched or electrically heated beyond the transition to the isotropic phase. We have found that the range of lasing wavelengths was in some cases considerably higher than when we optically stretched ordinary fluorescent oil droplets in our previous experiments.
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    PublicationOpen Access
    Glioma-on-a-chip models
    (Multidisciplinary Digital Publishing Institute (MDPI), 2021) İlçi, İrem Sultan; Department of Mechanical Engineering; N/A; N/A; Önder, Tuğba Bağcı; Taşoğlu, Savaş; Üstün, Merve; Dabbagh, Sajjad Rahmani; Faculty Member; Department of Mechanical Engineering; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); School of Medicine; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Social Sciences and Humanities; 184359; 291971; N/A; N/A
    Glioma, as an aggressive type of cancer, accounts for virtually 80% of malignant brain tumors. Despite advances in therapeutic approaches, the long-term survival of glioma patients is poor (it is usually fatal within 12-14 months). Glioma-on-chip platforms, with continuous perfusion, mimic in vivo metabolic functions of cancer cells for analytical purposes. This offers an unprecedented opportunity for understanding the underlying reasons that arise glioma, determining the most effective radiotherapy approach, testing different drug combinations, and screening conceivable side effects of drugs on other organs. Glioma-on-chip technologies can ultimately enhance the efficacy of treatments, promote the survival rate of patients, and pave a path for personalized medicine. In this perspective paper, we briefly review the latest developments of glioma-on-chip technologies, such as therapy applications, drug screening, and cell behavior studies, and discuss the current challenges as well as future research directions in this field.
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    PublicationOpen Access
    3D printed microneedles for point of care biosensing applications
    (Multidisciplinary Digital Publishing Institute (MDPI), 2022) Department of Mechanical Engineering; Sarabi, Misagh Rezapour; Nakhjavani, Sattar Akbar; Taşoğlu, Savaş; Faculty Member; Department of Mechanical Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Koç Üniversitesi İş Bankası Yapay Zeka Uygulama ve Araştırma Merkezi (KUIS AI)/ Koç University İş Bank Artificial Intelligence Center (KUIS AI); Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 291971
    Microneedles (MNs) are an emerging technology for user-friendly and minimally invasive injection, offering less pain and lower tissue damage in comparison to conventional needles. With their ability to extract body fluids, MNs are among the convenient candidates for developing biosensing setups, where target molecules/biomarkers are detected by the biosensor using the sample collected with the MNs. Herein, we discuss the 3D printing of microneedle arrays (MNAs) toward enabling point-of-care (POC) biosensing applications.
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    PublicationOpen Access
    Metamaterial based cloaking with sparse distribution of spiral resonators
    (Society of Photo-optical Instrumentation Engineers (SPIE), 2010) Saenz, Elena; Gonzalo, Roman; Özbay, Ekmel; Tretyakov, Sergei A.; Department of Physics; Güven, Kaan; Faculty Member; Department of Physics; College of Sciences; 52290
    We investigate the application of a metamaterial that is formed by the sparse distribution of spiral resonators as an optical transformation medium is in order to achieve electromagnetic cloaking. The well-known Clausius-Mossotti formula relates the microscopic polarizability of a single resonant particle to the macroscopic permittivity and permeability of the effective medium. By virtue of transformation optics, the permittivity and permeability of the medium, in turn, can be designed according to a coordinate transformation that maps a certain region of space to its surrounding. As a result, the mapped region can be cloaked from electromagnetic waves. In this study, the spirals are optimized to exhibit equal permittivity and permeability response so that the cloak formed by these spirals will work for both the TE and TM polarizations. An experimental setup is developed to visualize the steady state propagation of electromagnetic waves within a parallel plate waveguide including the cloaking structure. The measured and simulated electromagnetic field image indicates that the forward scattering of a metal cylinder is significantly reduced when placed within the cloak.