Researcher:
Begar, Efe

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PhD Student

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Efe

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Begar

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Begar, Efe

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2017 - 20185

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Researcher Of Publications: search.filters.isAuthorOfPublication.22431e82-a225-4dcf-8398-896276223c0b

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    3D coffee stains
    (Royal Soc Chemistry, 2017) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Department of Molecular Biology and Genetics; Department of Chemistry; Department of Chemistry; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Söz, Çağla Koşak; Press, Daniel Aaron; Melikov, Rustamzhon; Begar, Efe; Çonkar, Deniz; Karalar, Elif Nur Fırat; Yılgör, Emel; Yılgör, İskender; Nizamoğlu, Sedat; PhD Student; PhD Student; Researcher; PhD Student; PhD Student; PhD Student; PhD Student; Faculty Member; Researcher; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemistry; Department of Electrical and Electronics Engineering; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; N/A; N/A; N/A; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; College of Sciences; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 206349; N/A; 24181; 130295
    When a liquid droplet (e.g., coffee, wine, etc.) is splattered on a surface, the droplet dries in a ring-shaped stain. This widely observed pattern in everyday life occurs due to the phenomenon known as a coffee stain (or coffee ring) effect. While the droplet dries, the capillary flow moves and deposits the particles toward the pinned edges, which shows a 2D ring-like structure. Here we demonstrate the transition from a 2D to a 3D coffee stain that has a well-defined and hollow sphere-like structure, when the substrate surface is switched from hydrophilic to superhydrophobic. The 3D stain formation starts with the evaporation of the pinned aqueous colloidal droplet placed on a superhydrophobic surface that facilitates the particle flow towards the liquid-air interface. This leads to spherical skin formation and a cavity in the droplet. Afterwards the water loss in the cavity due to pervaporation leads to bubble nucleation and growth, until complete evaporation of the solvent. In addition to the superhydrophobicity of the surface, the concentration of the solution also has a significant effect on 3D coffee stain formation. Advantageously, 3D coffee stain formation in a pendant droplet configuration enables the construction of all-protein lasers by integrating silk fibroin with fluorescent proteins. No tools, components and/or human intervention are needed after the construction process is initiated; therefore, 3D coffee-stains hold promise for building self-assembled and functional 3D constructs and devices from colloidal solutions.
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    Single transverse mode eGFP modified silk fibroin laser
    (Optica Publishing Group (formerly OSA), 2018) Min, Kyungtaek; Umar, Muhammad; Kim, Sunghwan; N/A; N/A; N/A; N/A; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Jalali, Houman Bahmani; Begar, Efe; Çonkar, Deniz; Karalar, Elif Nur Fırat; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; N/A; N/A; N/A; 206349; 130295
    A single transverse mode distributed feedback laser is reported where the gain medium is composed enhanced green fluorescent protein in silk fibroin matrix. Moreover, optical feedback is increased with a high refractive index TiO<inf>2</inf> layer.
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    PublicationMetadata only
    All-protein 3D coffee stain lasers
    (Optica Publishing Group (formerly OSA), 2018) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Department of Molecular Biology and Genetics; Department of Chemistry; Department of Chemistry; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Söz, Çağla Koşak; Press, Daniel Aaron; Melikov, Rustamzhon; Begar, Efe; Çonkar, Deniz; Karalar, Elif Nur Fırat; Yılgör, Emel; Yılgör, İskender; Nizamoğlu, Sedat; PhD Student; PhD Student; Researcher; PhD Student; PhD Student; PhD Student; Faculty Member; Researcher; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemistry; Department of Electrical and Electronics Engineering; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; N/A; N/A; N/A; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; College of Sciences; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 206349; N/A; 24181; 130295
    The transition from a 2D to a 3D coffee stain that has a well-defined and hollow spherelike structure is demonstrated. Self-assembled all-protein lasers are constructed by 3D coffee stains.
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    PublicationOpen Access
    Single transverse mode protein laser
    (American Institute of Physics (AIP) Publishing, 2017) Min, Kyungtaek; Kim, Sunghwan; Umar, Muhammad; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Jalali, Houman Bahmani; Begar, Efe; Çonkar, Deniz; Karalar, Elif Nur Fırat; Nizamoğlu, Sedat; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Electrical and Electronics Engineering; College of Sciences; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A; N/A; 130295
    Here, we report a single transverse mode distributed feedback (DFB) protein laser. The gain medium that is composed of enhanced green fluorescent protein in a silk fibroin matrix yields a waveguiding gain layer on a DFB resonator. The thin TiO2 layer on the quartz grating improves optical feedback due to the increased effective refractive index. The protein laser shows a single transverse mode lasing at the wavelength of 520 nm with the threshold level of 92.1 mu J/mm(2).
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    PublicationOpen Access
    Silk-based aqueous microcontact printing
    (American Chemical Society (ACS), 2018) Department of Electrical and Electronics Engineering; N/A; Department of Physics; Department of Molecular Biology and Genetics; Kumar, Baskaran Ganesh; Melikov, Rustamzhon; Aria, Mohammad Mohammadi; Yalçın, Aybike Ural; Begar, Efe; Sadeghi, Sadra; Güven, Kaan; Nizamoğlu, Sedat; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Physics; Department of Molecular Biology and Genetics; College of Engineering; Graduate School of Sciences and Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 52290; 130295
    Lithography, the transfer of patterns to a film or substrate, is the basis by which many modern technological devices and components are produced. However, established lithographic approaches generally use complex techniques, expensive equipment, and advanced materials. Here, we introduce a water-based microcontact printing method using silk that is simple, inexpensive, ecofriendly, and recyclable. Whereas the traditional microcontact printing technique facilitates only negative lithography, the synergetic interaction of the silk, water, and common chemicals in our technique enables both positive and negative patterning using a single stamp. Among diverse application possibilities, we exemplify a proof of concept of the method through optimizing its metal lift-off process and demonstrate the fabrication of electromagnetic metamaterial elements on both solid and flexible substrates. The results indicate that the method demonstrated herein is universally applicable to device production and technology development.