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Publication Metadata only A computational study of drop formation in an axisymmetric flow-focusing device(Amer Soc Mechanical Engineers, 2006) Department of Mechanical Engineering; Department of Mechanical Engineering; Filiz, İsmail; Muradoğlu, Metin; N/A; Faculty Member; Department of Mechanical Engineering; College of Engineering; College of Engineering; N/A; 46561We investigate the formation and dynamics of drops computationally in an axisymetric geometry using a Front-Tracking/Finite-Difference (FT/FD) method. The effects of viscosity ratio between inner and outer liquids on the drop creation process and drop size distribution are examined. It is found that the viscosity ratio critically influences the drop formation process and the final drop distribution. We found that, for small viscosity ratios, i.e., 0.1 < lambda < 0.5 drop size is about the size of the orifice and drop distribution is highly monodisperse. When viscosity ratio is increased, i.e., 0.5 < lambda < I a smaller drop is created just after the main drop. For even higher viscosity ratios, the drop distribution is usually monodisperse but a satellite drop is created in some cases. The effect of the flow rates in the inner jet and the co flowing annulus are also studied. It is found that the drop size gets smaller as Q(in) / Q(out) is reduced while keeping the outer flow rate constant.Publication Metadata only A magnetically actuated resonant mass sensor with integrated optical readout(Ieee-Inst Electrical Electronics Engineers Inc, 2008) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Öztürk, Alibey; Ocaklı, Hüseyin İlker; Özber, Natali; Ürey, Hakan; Kavaklı, İbrahim Halil; Alaca, Burhanettin Erdem; Master Student; Researcher; Master Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; 8579; 40319; 115108Nickel cantilevers with integrated diffraction gratings are used as resonant mass sensors with a resolution of 500 femtograms. Their applicability to biosensing is demonstrated with human opioid receptors. The device is fabricated through a single-mask lithographic process. The microoptical readout provides a simple measurement platform with one external photodiode. Thanks to its ac operation principle, the device is immune to environmental noise and entails a high tolerance to fabrication defects. Obtained signal-to-noise ratio is comparable to that of a high-end Doppler vibrometer. The device with these aspects for systems integration and microarray technology is a candidate for low-cost portable sensors.Publication Open Access Broadband and band-limited random vibration energy harvesting using a piezoelectric patch on a thin plate(Society of Photo-optical Instrumentation Engineers (SPIE), 2014) Erturk, Alper; Department of Mechanical Engineering; Arıdoğan, Mustafa Uğur; Başdoğan, İpek; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179940This paper presents analytical modeling and case studies of broadband and band-limited random vibration energy harvesting using a piezoceramic patch attached on a thin plate. The literature of vibration-based energy harvesting has been mostly focused on resonant cantilevered structures. However, cantilevered beam-type harvesters have limited broadband vibration energy harvesting capabilities unless they are combined with a nonlinear component. Moreover, cantilever arrangements cannot always be mounted on thin structures (which are basic components of marine, aerospace, and ground transportation systems) without significantly affecting the host system's design and overall dynamics. A patch-based piezoelectric energy harvester structurally integrated to a thin plate can be a proper alternative to using resonant cantilevers for harvesting energy from thin structures. Besides, plate-like structures have more number of vibration modes compared to beam structures, offering better broadband performance characteristics. In this paper, we present analytical modelling of patch-based piezoelectric energy harvester attached on a thin plate for random vibrations. The analytical model is based on electromechanically-coupled distributed-parameter formulation and validated by comparing the electromechanical frequency response functions (FRFs) with experimental results. Example case studies are then presented to investigate the expected power output of a piezoceramic patch attached on an aluminum plate for the case of random force excitations. The effect of bandwidth of random excitation on the mean power and shunted mean-square vibration response are explored with a focus on the number of vibration modes covered in the frequency range of input power spectral density (PSD).Publication Metadata only Controlled observation of nondegenerate cavity modes in a microdroplet on a superhydrophobic surface(Elsevier, 2009) Department of Physics; Department of Physics; Department of Mechanical Engineering; Department of Mechanical Engineering; Department of Physics; Yorulmaz, Saime Çiğdem; Mestre, Michael; Muradoğlu, Metin; Alaca, Burhanettin Erdem; Kiraz, Alper; Master Student; Researcher; Faculty Member; Faculty Member; Faculty Member; Department of Mechanical Engineering; Department of Physics; College of Engineering; College of Engineering; College of Engineering; College of Engineering; College of Sciences; N/A; N/A; 46561; 115108; 22542We demonstrate controlled lifting of the azimuthal degeneracy of the whispering gallery modes (WGMs) of single glycerol-water microdroplets standing on a superhydrophobic surface by using a uniform electric field. A good agreement is observed between the measured spectral positions of the nondegenerate WGMs and predictions made for a prolate spheroid. Our results reveal fewer azimuthal modes than expected from an ideal spherical microdroplet due to the truncation by the surface. We use this difference to estimate the contact angles of the microdroplets.Publication Open Access Dynamic characterization and damping control of a MEMS structure - art. no. 671509(Society of Photo-optical Instrumentation Engineers (SPIE), 2007) Department of Mechanical Engineering; Alaca, Ilgım Veryeri; Başdoğan, İpek; Faculty Member; Department of Mechanical Engineering; College of Engineering; 50569; 179940Publication Open Access Fabrication of optical nanodevices through field-emission scanning probe lithography and cryogenic etching(Society of Photo-optical Instrumentation Engineers (SPIE), 2018) Aydoğan, Cemal; Hofmann, Martin; Lenk, Claudia; Volland, Burkhard; Rangelow, Ivo W.; Ateş, Onur; Torun, Hamdi; Yalcinkaya, Arda D.; Department of Mechanical Engineering; Alaca, Burhanettin Erdem; Biçer, Mahmut; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; 115108; N/ASub-10 nanometer lithography is opening a new area for beyond-CMOS devices. Regarding to single nano-digit manufacturing we have established a new maskless patterning scheme by using field-emission, current controlled Scanning Probe Lithography (cc-SPL) in order to create optical nanodevices in thin silicon-oninsulator (SOI) substrates. This work aims to manufacture split ring resonators into calixarene resist by using SPL, while plasma etching at cryogenic temperatures is applied for an efficient pattern transfer into the underlying Si layer. Such electromagnetic resonators take the form of a ring with a narrow gap, whose 2D array was the first left-handed material tailored to demonstrate the so-called left-hand behavior of the wave propagation. It is shown that the resonance frequency can be tuned with the feature size of the resonator, and the resonance frequency can be shifted further into near infrared or even visible light regions.Publication Open Access Field-emission scanning probe lithography with self-actuating and self-sensing cantilevers for devices with single digit nanometer dimensions(Society of Photo-optical Instrumentation Engineers (SPIE), 2018) Rangelow, Ivo W.; Lenk, Claudia; Hofmann, Martin; Lenk, Steve; Ivanov, Tzvetan; Ahmad, Ahmad; Kaestner, Marcus; Guliyev, Elshad; Reuter, Christoph; Budden, Matthias; Zoellner, Jens-Peter; Holz, Mathias; Reum, Alexander; Durrani, Zahid; Jones, Mervyn; Aydoğan, Cemal; Kuehnel, Michael; Frohlich, Thomas; Fuessl, Roland; Manske, E.; Department of Mechanical Engineering; Alaca, Burhanettin Erdem; Biçer, Mahmut; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; 115108; N/ACost-effective generation of single-digit nano-lithographic features could be the way by which novel nanoelectronic devices, as single electron transistors combined with sophisticated CMOS integrated circuits, can be obtained. The capabilities of Field-Emission Scanning Probe Lithography (FE-SPL) and reactive ion etching (RIE) at cryogenic temperature open up a route to overcome the fundamental size limitations in nanofabrication. FE-SPL employs Fowler-Nordheim electron emission from the tip of a scanning probe in ambient conditions. The energy of the emitted electrons (<100 eV) is close to the lithographically relevant chemical excitations of the resist, thus strongly reducing proximity effects. The use of active, i.e. self-sensing and self-actuated, cantilevers as probes for FE-SPL leads to several promising performance benefits. These include: (1) Closed-loop lithography including pre-imaging, overlay alignment, exposure, and post-imaging for feature inspection; (2) Sub-5-nm lithographic resolution with sub-nm line edge roughness; (3) High overlay alignment accuracy; (4) Relatively low costs of ownership, since no vacuum is needed, and ease-of-use. Thus, FE-SPL is a promising tool for rapid nanoscale prototyping and fabrication of high resolution nanoimprint lithography templates. To demonstrate its capabilities we applied FE-SPL and RIE to fabricate single electron transistors (SET) targeted to operate at room temperature. Electrical characterization of these SET confirmed that the smallest functional structures had a diameter of only 1.8 nanometers. Devices at single digit nano-dimensions contain only a few dopant atoms and thus, these might be used to store and process quantum information by employing the states of individual atoms.Publication Metadata only Haptic guidance for improved task performance in steering microparticles with optical tweezers(Optical Soc Amer, 2007) Department of Mechanical Engineering; Department of Physics; N/A; N/A; Department of Physics; Başdoğan, Çağatay; Kiraz, Alper; Büküşoğlu, İbrahim; Varol, Aydın; Doğanay, Sultan; Faculty Member; Faculty Member; Master Student; Master Student; Undergraduate Student; Department of Mechanical Engineering; Department of Physics; College of Engineering; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; 125489; 22542; N/A; N/A; N/AWe report the manipulation of 4-5 mu m diameter polymer microspheres floating in water using optical tweezers (OT) and a haptic device (i.e. force-reflecting robotic arm). Trapped microspheres are steered using the end-effector of a haptic device that is virtually coupled to an XYZ piezo-scanner controlling the movements of the fluid bed. To help with the manipulations, we first calculate a collision-free path for the particle and then display artificial guidance forces to the user through the haptic device to keep him/her on this path during steering. Experiments conducted with 8 subjects show almost two-fold improvements in the average path error and average speed under the guidance of haptic feedback. (c) 2007 Optical Society of America.Publication Open Access Immersive haptic interaction with media(Society of Photo-optical Instrumentation Engineers (SPIE), 2010) Dindar, N.; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; Tekalp, Ahmet Murat; Başdoğan, Çağatay; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Mechanical Engineering; College of Engineering; 26207; 125489New 3D video representations enable new modalities of interaction, such as haptic interaction, with 2D and 3D video for truly immersive media applications. Haptic interaction with video includes haptic structure and haptic motion for new immersive experiences. It is possible to compute haptic structure signals from 3D scene geometry or depth information. This paper introduces the concept of haptic motion, as well as new methods to compute haptic structure and motion signals for 2D video-plus-depth representation. The resulting haptic signals can be rendered using a haptic cursor attached to a 2D or 3D video display.Publication Metadata only Monolithic technology for silicon nanowires in high-topography architectures(Elsevier, 2017) Wollschlager, Nicole; Rangelow, Ivo W.; Leblebici, Yusuf; Department of Mechanical Engineering; Esfahani, Mohammad Nasr; Yılmaz, Mustafa Akın; Alaca, Burhanettin Erdem; PhD Student; PhD Student; Faculty Member; 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; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 115108Integration of silicon nanowires (Si NWs) in three-dimensional (3D) devices including integrated circuits (ICs) and microelectromechanical systems (MEMS) leads to enhanced functionality and performance in diverse applications. The immediate challenge to the extensive use of Si NWs in modern electronic devices is their integration with the higher-order architecture. Topography-related limits of integrating Si NWs in the third dimension are addressed in this work. Utilizing a well-tuned combination of etching and protection processes, Si NWs are batch-produced in bulk Si with an extreme trench depth of 40 gm, the highest trench depth obtained in a monolithic fashion within the same Si crystal so far. The implications of the technique for the thick silicon-on-insulator (S01) technology are investigated. The process is transferred to SOI wafers yielding Si NWs with a critical dimension of 100 nm along with a trench aspect ratio of 50. Electrical measurements verify the prospect of utilizing such suspended Si NWs spanning deep trenches as versatile active components in ICs and MEMS. Introducing a new monolithic approach to obtaining Si NWs and the surrounding higher-order architecture within the same SOI wafer, this work opens up new possibilities for modem sensors and power efficient ICs. (C) 2017 Elsevier B.V. All rights reserved.