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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only IDE-integrated microneedle arrays as fully biodegradable platforms for wearable/implantable capacitive biosensing(Institute of Electrical and Electronics Engineers Inc., 2023) Department of Electrical and Electronics Engineering; Ürey, Hakan; Mirzajani, Hadi; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of EngineeringMicroneedle biosensors have emerged as a promising tool for in situ biomarker detection due to their minimally invasive nature and ability to interface with interstitial fluid (ISF). However, most previously demonstrated ones are limited to in situ detection of small molecules and ions, employing amperometry or potentiometry measurement techniques with electrical current or voltage output metrics, respectively, which may not be suitable for detecting large molecules, such as proteins. This letter presents an innovative approach utilizing a microneedle array integrated with an interdigitated electrode (MAIDE), enabling in situ capacitive detection and quantification of protein biomarkers. Following microneedle penetration, the interdigitated electrode array establishes direct contact with the solution, enabling real-time monitoring of interfacial capacitance modulations as the result of the binding reaction, leading to the acquisition of rich molecular data. Equivalent circuit model extraction followed by impedance spectroscopy for different concentrations of bovine serum albumin (BSA) indicated the suitability of the proposed platform in tracking the interfacial capacitance variations with respect to different BSA concentrations of 100, 10, and 1 μg/mL with a detection limit of 21 ng/mL. Furthermore, the device showed satisfactory results for biodegradability experiments where it disintegrated for a duration of 10 h. In addition, in vivo experiments show stable capacitance readings with (dC/C)% deviations less than 0.5%, indicating its potential for biodegradable wearable/implantable capacitive biosensing applicationsPublication Metadata only PhysioPatch: a multimodal and adaptable wearable patch for cardiovascular and cardiopulmonary assessment(IEEE-Inst Electrical Electronics Engineers Inc, 2024) ; Department of Electrical and Electronics Engineering; Hayırlıoğlu, Yusuf Ziya; Gürsoy, Beren Semiz; Department of Electrical and Electronics Engineering; ; Graduate School of Sciences and Engineering; College of Engineering;Remote monitoring systems offer significant advantages in assessing cardiovascular and cardiopulmonary health, facilitating early diagnosis and enabling personalized treatment plans. In this article, we present a novel wearable patch, PhysioPatch, which could facilitate comprehensive monitoring of cardiovascular and cardiopulmonary functions by simultaneously capturing various physiological signals, including electrocardiogram (ECG), seismocardiogram (SCG), photoplethysmogram (PPG), and body temperature. The design comprises a main body intended for placement on the mid-sternum and a detachable daughter body, enabling distal measurements to enhance comprehensive assessment. While the main body includes the sensors for measuring the body temperature, ECG, proximal PPG and SCG signals, and other electronics such as the microcontroller, the battery, the battery management system (BMS), the Bluetooth, and the microSD card;the daughter body houses the sensors for distal pulse vibration and PPG signal acquisition. Along with the system design, the algorithms to derive various hemodynamic parameters (heart rate (HR), HR variability (HRV), respiration rate, and oxygen saturation) are also presented. The system was validated with a human subject study including 20 participants, and the results have revealed that the PhysioPatch is capable of achieving high-quality signals, resulting in accurate derivation of hemodynamic parameters. Overall, such a system could potentially offer continuous health monitoring outside clinical settings, regardless of time and environmental stressors.Publication Metadata only Silk as a biodegradable resist for field-emission scanning probe lithography(Institute of Physics (IOP) Publishing, 2020) Sadeghi, Sadra; Rangelow, Ivo W.; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; N/A; N/A; Department of Electrical and Electronics Engineering; Alaca, Burhanettin Erdem; Kumar, Baskaran Ganesh; Melikov, Rustamzhon; Doğru-Yüksel, Itır Bakış; Nizamoğlu, Sedat; Faculty Member; Other; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Department of Electrical and Electronics Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştirmalari Merkezi (KUYTAM); N/A; N/A; N/A; N/A; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 115108; N/A; N/A; N/A; 130295The patterning of silk allows for manufacturing various structures with advanced functionalities for optical and tissue engineering and drug delivery applications. Here, we propose a high-resolution nanoscale patterning method based on field-emission scanning probe lithography (FE-SPL) that crosslinks the biomaterial silk on conductive indium tin oxide (ITO) promoting the use of a biodegradable material as resist and water as a developer. During the lithographic process, Fowler-Nordheim electron emission from a sharp tip was used to manipulate the structure of silk fibroin from random coil to beta sheet and the emission formed nanoscale latent patterns with a critical dimension (CD) of similar to 50 nm. To demonstrate the versatility of the method, we patterned standard and complex shapes. This method is particularly attractive due to its ease of operation without relying on a vacuum or a special gaseous environment and without any need for complex electronics or optics. Therefore, this study paves a practical and cost-effective way toward patterning biopolymers at ultra-high level resolution.Publication Metadata only Modeling and characterization of comb-actuated resonant microscanners(Iop Publishing Ltd, 2006) N/A; Department of Electrical and Electronics Engineering; Ataman, Çağlar; Ürey, Hakan; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 8579The dynamics of the out-of-plane comb-drive actuator used in a torsional resonant mode microscanner is discussed. The microscanner is fabricated using the standard SOI technology by Fraunhofer, IPMS and utilized in various display, barcode scanning, spectroscopy and other imaging applications. The device is a parametrically excited system and exhibits hysteretic frequency response, nonlinear transient response, subharmonic oscillations, multiple parametric resonances, and alternating-oscillation-frequency behavior. Analytical and numerical models are developed to predict the parametric system dynamics. The analytical model is based on the solution of the linear Mathieu equation and valid for small angular displacements. The numerical model is valid for both small and large deflection angles. The analytical and numerical models are validated with the experimental results under various ambient pressures and excitation schemes and successfully predict the dynamics of the parametric nature of the microscanner. As many as four parametric resonances are observed at 30 mTorr. The models developed in this paper can be used to optimize the structure and the actuator.Publication Metadata only Comb-actuated resonant torsional microscanner with mechanical amplification(IEEE-Inst Electrical Electronics Engineers Inc, 2010) Brown, Dean; Davis, Wyatt O.; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; N/A; Department of Electrical and Electronics Engineering; Arslan, Aslıhan; Holmstrom, Sven; Gökçe, Sertan Kutal; Ürey, Hakan; Researcher; Researcher; Master Student; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 8579A comb-actuated torsional microscanner is developed for high-resolution laser-scanning display systems. Typical torsional comb-drive scanners have fingers placed around the perimeter of the scanning mirror. In contrast, the structure in this paper uses cascaded frames, where the comb fingers are placed on an outer drive frame, and the motion is transferred to the inner mirror frame with a mechanical gain. The structure works only in resonant mode without requiring any offset in the comb fingers, keeping the silicon-on-insulator-based process quite simple. The design intent is to improve actuator efficiency by removing the high-drag fingers from the high-velocity scanning mirror. Placing them on the lower velocity drive frame reduces their contribution to the damping torque. Furthermore, placement on the drive frame allows an increase of the number of fingers and their capacity to impart torque. The microscanner exhibits a parametric response, and as such, the maximum deflection is found when actuated at twice its natural frequency. Analytical formulas are given for the coupled-mode equations and frame deflections. A simple formula is derived for the mechanical-gain factor. For a 1-mm x 1.5-mm oblong scanning mirror, a 76. total optical scan angle is achieved at 21.8 kHz with 196-V peak-to-peak excitation voltages. [2009-0304]Publication Metadata only Resonance fluorescence in a waveguide geometry(IEEE, 2012) Rephaeli, Eden; Fan, Shanhui; Department of Electrical and Electronics Engineering; Kocabaş, Şükrü Ekin; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; N/AWe show how to calculate the first-and second-order statistics of the scattered fields for an arbitrary intensity coherent-state light field interacting with a two-level system in a waveguide geometry. Specifically, we calculate the resonance fluorescence from the qubit, using input-output formalism. We derive the transmission and reflection coefficients, and illustrate the bunching and antibunching of light that is scattered in the forward and backward directions, respectively. Our results agree with previous calculations on one-and two-photon scattering as well as those that are based on the master equation approach.Publication Metadata only Electromagnetically actuated FR4 scanners(IEEE-Inst Electrical Electronics Engineers Inc, 2008) Yalcinkaya, Arda D.; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Ürey, Hakan; Holmstrom, Sven; Faculty Member; Researcher; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; 8579; N/AA torsional micromechanical scanner is fabricated from thin Fire Resistant 4 substrates using standard printed circuit board technology. The top and the bottom copper layers are connected with vias and shaped as a single coil to enable one- and two-dimensional electromagnetic actuation with an external magnet. Using 5 mm x 5 mm mirrors, the following scan angle and resonant frequency combinations are achieved: 17 degrees at 1.8 kHz and 140 degrees at 417 Hz. Another 10 x improvement in magnetic actuation torque seems feasible. The technology offers a unique advantage by allowing a high degree of integration with microoptics and electronics directly on the mechanical platform and offers a low-cost alternative to silicon microelectromechanical systems devices particularly when large or low-frequency devices are required.Publication Metadata only Understanding fundamental trade-offs in nanomechanical resonant sensors(Amer Inst Physics, 2021) Department of Electrical and Electronics Engineering; Demir, Alper; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 3756Publication Metadata only Examining lightning channel electrical properties with time domain fractal lightning modeling(IEEE, 2011) Cohen M.B.; Carlson B.E.; Liang, Can; Lehtinen N.G.; Lauben D.S.; Department of Electrical and Electronics Engineering; İnan, Umran Savaş; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 177880The electrical properties of the lightning channel are determined by a complex interplay of dielectric breakdown, plasma heating, expansion, and cooling. These details are observable through their effect on the channel current and electromagnetic wave emissions. This suggests that electromagnetic observations of lightning can be used to study channel physics and behavior. This paper presents the Time Domain Fractal Lightning model (TDFL), a high-level tool that connects channel electrical properties to charge and current flow for branched, tortuous lightning channels. The TDFL extends ideas of fractal discharges to the time domain through the retarded time electric field integral equation. Here we present a preliminary application of the TDFL to stepped leader extension and compare the predicted electromagnetic emissions to observations. The results show crude qualitative agreement, demonstrating that more complex channel behavior should be included and that such behavior can be studied with high-level tools like the TDFL.Publication Metadata only Uncooled thermo-mechanical detector array with optical readout(Walter De Gruyter Gmbh, 2006) N/A; N/A; Department of Electrical and Electronics Engineering; Torun, Hamdi; Ürey, Hakan; Master Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 8579This paper reports a novel uncooled infrared FPA whose performance is comparable to the cooled FPA's in terms of noise parameters. FPA consists of bimaterial microcantilever structures that are designed to convert IR radiation energy into mechanical energy. Induced deflection by mechanical energy is detected by means of optical methods that measure sub nanometer thermally induced deflections. Analytical solutions are developed for calculating the figure of merits for the FPA. FEM simulations and the analytical solution agree well. Calculations show that for an FPA, NETD of < 5 mK is achievable in the 8-12 pm band. The design and optimization for the detectors are presented. The mechanical structure of pixels is designed such that it can be possible to form large array size FPA's. Microfabrication of the devices to improve the performance further; employs low cost standard MEMS processes.