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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access An information theoretical analysis of broadcast networks and channel routing for FRET-based nanoscale communications(Institute of Electrical and Electronics Engineers (IEEE), 2012) Kuşcu, Murat; Malak, Derya; Akan, Özgür Barış; Faculty Member; College of EngineeringNanoscale communication based on Forster Resonance Energy Transfer (FRET) enables nanomachines to communicate with each other using the excited state of the fluorescent molecules as the information conveyer. In this study, FRET-based nanoscale communication is further extended to realize FRET-based nanoscale broadcast communication with one transmitter and many receiver nanomachines, and the performance of the broadcast channel is analyzed information theoretically. Furthermore, an electrically controllable routing mechanism is proposed exploiting the Quantum Confined Stark Effect (QCSE) observed in quantum dots. It is shown that by appropriately selecting the employed molecules on the communicating nanomachines, it is possible to control the route of the information flow by externally applying electric field in FRET-based nanonetworks.Publication Open Access In situ formation of copper phosphate on hydroxyapatite for wastewater treatment(Multidisciplinary Digital Publishing Institute (MDPI), 2022) Rahmani, Fatemeh; Ghadi, Arezoo; Khaksar, Samad; Doustkhah, Esmail; PhD Student; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM)Here, we control the surface activity of hydroxyapatite (HAp) in wastewater treatment which undergoes peroxodisulfate (PDS) activation. Loading the catalytically active Cu species on HAp forms a copper phosphate in the outer layer of HAp. This modification turns a low active HAp into a high catalytically active catalyst in the dye degradation process. The optimal operational conditions were established to be [Cu-THAp](0) = 1 g/L, [RhB](0) = 20 mg/L, [PDS](0) = 7.5 mmol/L, and pH = 3. The experiments indicate that the simultaneous presence of Cu-THAp and PDS synergistically affect the degradation process. Additionally, chemical and structural characterizations proved the stability and effectiveness of Cu-THAp. Therefore, this work introduces a simple approach to water purification through green and sustainable HAp-based materials.Publication Open Access Nonlinear nanomechanical mass spectrometry at the single-nanoparticle level(American Chemical Society (ACS), 2019) Yüksel, Mert; Orhan, Ezgi; Yanık, Cenk; Arı, Atakan B.; Hanay, M. Selim; Department of Electrical and Electronics Engineering; Demir, Alper; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 3756Nanoelectromechanical systems (NEMS) have emerged as a promising technology for performing the mass spectrometry of large biomolecules and nanoparticles. As nanoscale objects land on NEMS sensors one by one, they induce resolvable shifts in the resonance frequency of the sensor proportional to their weight. The operational regime of NEMS sensors is often limited by the onset of nonlinearity, beyond which the highly sensitive schemes based on frequency tracking by phase-locked loops cannot be readily used. Here, we develop a measurement architecture with which to operate at the nonlinear regime and measure frequency shifts induced by analytes in a rapid and sensitive manner. We used this architecture to individually characterize the mass of gold nanoparticles and verified the results by performing independent measurements of the same nanoparticles based on linear mass sensing. Once the feasibility of the technique is established, we have obtained the mass spectrum of a 20 nm gold nanoparticle sample by individually recording about 500 single-particle events using two modes working sequentially in the nonlinear regime. The technique obtained here can be used for thin nanomechanical structures that possess a limited dynamic range.Publication Open Access Coverage and throughput analysis for FRET-based mobile molecular sensor/actor nanonetworks(Elsevier, 2014) Kuşcu, Murat; Akan, Özgür Barış; Faculty Member; College of EngineeringNanonetworks are envisaged to expand the capabilities of single nanomachines by enabling collaboration through communication between them. Forster Resonance Energy Transfer (FRET) observed among fluorescent molecules is a promising means of high-rate and reliable information transfer between single fluorophore-based nanoscale molecular machines. Recent theoretical studies have underlined its practicality for mobile ad hoc nanonetworks consisting of functionalized fluorescent molecules. In this study, we focus on the spatial characteristics of FRET-Based Mobile Molecular Sensor/Actor Nanonetworks (FRET-MSAN) by investigating the network performance in terms of communication coverage, network throughput and information propagation rate through extensive Monte Carlo simulations. The effect of fundamental system parameters related to FRET and to the mobility of the network nodes on the network performance is revealed. The results of the simulations indicate that the throughput and propagation rate as a function of distance from the information source are well-fitted by exponential curves. We also observe that the impact of FRET mechanism suppresses the effect of Brownian motion of network nodes on the exciton mobility.Publication Open Access Employing 60 GHz ISM band for 5G wireless communications(Institute of Electrical and Electronics Engineers (IEEE), 2014) Fadel, Etimad; Yılmaz, Türker; Akan, Özgür Barış; College of EngineeringWireless data traffic is continuously increasing due to the steady rise in both connected device number and traffic per device. Wireless networks, traditionally confined below 6 giga-hertz, are getting clogged and unable to satisfy the ever-increasing demands of its users. Already aware of this, telecommunications industry and academia have been working on solutions. One of the main methods for throughput increase is operation bandwidth expansion; however, sufficient spectrum is not available within the conventional frequencies. Following various considerations, 60 GHz industrial, scientific and medical radio band has been selected as the new spectrum to be utilized and wireless personal and local area network standards for the band are already completed. In line with the stated developments, this paper proposes the use of 60 GHz band for the fifth generation (5G) communication systems. After very briefly setting the scene of the current wireless communication networks, the physical layer properties of the 60 GHz band are presented. A representative indoor simulation between the fourth generation and proposed 5G cases is set and performed. The results are assessed and compared before concluding the paper.Publication Open 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/ANanoscale 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.Publication Open Access Minimum energy channel codes for nanoscale wireless communications(Institute of Electrical and Electronics Engineers (IEEE), 2013) Department of Electrical and Electronics Engineering; Kocaoğlu, Murat; Akan, Özgür Barış; PhD Student; Department of Electrical and Electronics Engineering; College of EngineeringIt is essential to develop energy-efficient communication techniques for nanoscale wireless communications. In this paper, a new modulation and a novel minimum energy coding scheme (MEC) are proposed to achieve energy efficiency in wireless nanosensor networks (WNSNs). Unlike existing studies, MEC maintains the desired code distance to provide reliability, while minimizing energy. It is analytically shown that, with MEC, codewords can be decoded perfectly for large code distances, if the source set cardinality is less than the inverse of the symbol error probability. Performance evaluations show that MEC outperforms popular codes such as Hamming, Reed-Solomon and Golay in the average codeword energy sense.Publication Open Access Nanoscale communication with molecular arrays in nanonetworks(Institute of Electrical and Electronics Engineers (IEEE), 2012) Galmes, Sebastia; Atakan, Barış; Akan, Özgür Barış; PhD Student; Faculty Member; College of EngineeringMolecular communication is a promising nanoscale communication paradigm that enables nanomachines to exchange information by using molecules as communication carrier. Up to now, the molecular communication channel between a transmitter nanomachine (TN) and a receiver nanomachine (RN) has been modeled as either concentration channel or timing channel. However, these channel models necessitate exact time synchronization of the nanomachines and provide a relatively low communication bandwidth. In this paper, the Molecular ARray-based COmmunication (MARCO) scheme is proposed, in which the transmission order of different molecules is used to convey molecular information without any need for time synchronization. The MARCO channel model is first theoretically derived, and the intersymbol interference and error probabilities are obtained. Based on the error probability, achievable communication rates are analytically obtained. Numerical results and performance comparisons reveal that MARCO provides significantly higher communication rate, i.e., on the scale of 100 Kbps, than the previously proposed molecular communication models without any need for synchronization. More specifically, MARCO can provide more than 250 Kbps of molecular communication rate if intersymbol time and internode distance are set to 2 mu s and 2 nm, respectively.Publication Open Access Temperature control in dissipative cavities by entangled dimers(American Chemical Society (ACS), 2019) Dağ, Ceren B.; Niedenzu, Wolfgang; Özaydın, Fatih; Kurizki, Gershon; Department of Physics; Müstecaplıoğlu, Özgür Esat; Faculty Member; Department of Physics; College of Sciences; 1674We show that the temperature of a cavity field can be drastically varied by its interaction with suitably entangled atom pairs (dimers) traversing the cavity under realistic atomic decoherence. To this end we resort to the hitherto untapped resource of naturally entangled dimers whose state can be simply controlled via molecular dissociation, collisions forming the dimer, or unstable dimers such as positronium. Depending on the chosen state of the dimer, the cavity-field mode can be driven to a steady-state temperature that is either much lower or much higher than the ambient temperature, despite adverse effects of cavity loss and atomic decoherence. Entangled dimers enable much broader range of cavity temperature control than single "phaseonium" atoms with coherently superposed levels. Such dimers are shown to constitute highly caloric fuel that can ensure high efficiency or power in photonic thermal engines. Alternatively, they can serve as controllable thermal baths for quantum simulation of energy exchange in photosynthesis or quantum annealing.Publication Open Access Computational screening of MOF-based mixed matrix membranes for CO2/N2 separations(Hindawi, 2016) Department of Chemical and Biological Engineering; Keskin, Seda; Sümer, Zeynep; Master Student; Department of Chemical and Biological Engineering; College of Engineering; Graduate School of Sciences and Engineering; 40548; N/AAtomically detailed simulations were used to examine CO2/N-2 separation potential of metal organic framework- (MOF-) based mixed matrix membranes (mmms) in this study. Gas permeability and selectivity of 700 new mmms composed of 70 different mofs and 10 different polymers were calculated for CO2/N-2 separation. This is the largest number of MOF-based mmms for which computational screening is done to date. Selecting the appropriate mofs as filler particles in polymers resulted in mmms that have higher CO2/N-2 selectivities and higher CO2 permeabilities compared to pure polymer membranes. We showed that, for polymers that have low CO2 permeabilities but high CO2 selectivities, the identity of the MOF used as filler is not important. All mofs enhanced the CO2 permeabilities of this type of polymers without changing their selectivities. Several MOF-based mmms were identified to exceed the upper bound established for polymers. The methods we introduced in this study will create many opportunities to select the MOF/polymer combinations with useful properties for CO2 separation applications.