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Publication Open Access 3D-printed microneedles in biomedical applications(Elsevier, 2021) Rahbarghazi, Reza; Yetişen, Ali Kemal; N/A; Department of Mechanical Engineering; Dabbagh, Sajjad Rahmani; Sarabi, Misagh Rezapour; Sokullu, Emel; Taşoğlu, Savaş; Faculty Member; 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); Graduate School of Social Sciences and Humanities; Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; N/A; N/A; 163024; 291971Conventional needle technologies can be advanced with emerging nano- and micro-fabrication methods to fabricate microneedles. Nano-/micro-fabricated microneedles seek to mitigate penetration pain and tissue damage, as well as providing accurately controlled robust channels for administrating bioagents and collecting body fluids. Here, design and 3D printing strategies of microneedles are discussed with emerging applications in biomedical devices and healthcare technologies. 3D printing offers customization, cost-efficiency, a rapid turnaround time between design iterations, and enhanced accessibility. Increasing the printing resolution, the accuracy of the features, and the accessibility of low-cost raw printing materials have empowered 3D printing to be utilized for the fabrication of microneedle platforms. The development of 3D-printed microneedles has enabled the evolution of pain-free controlled release drug delivery systems, devices for extracting fluids from the cutaneous tissue, biosignal acquisition, and point-of-care diagnostic devices in personalized medicine.Publication Open Access Biophotonic sensor applications based on photonic atoms - art. no. 60990Q(Society of Photo-optical Instrumentation Engineers (SPIE), 2006) Demir, Abdullah; Department of Physics; Serpengüzel, Ali; Faculty Member; Department of Physics; College of Sciences; 27855Microsphere resonators, i.e., photonic atoms, have found wide area of application in optical spectroscopy, quantum optics, cavity QED, switching, and sensing. Photonic atoms have unique optical properties such as high quality factor (Q-factor) morphology dependent resonances (MDR's), and relatively small volumes. High-Q MDR's are very sensitive to the refractive index change and microsphere uniformity. These tiny optical cavities, whose diameters vary from a few to several hundred micrometers, have resonances with reported Q-factors as large as 3x10(9). Due to their sensitivity, MDR's are also considered for biosensor applications. Binding of a protein or other biomolecules can be monitored by observing the wavelength shift of MDR's. A biosensor, based on this optical phenomenon, can even detect a single molecule, depending on the quality of the system. In this work, elastic scattering spectra from photonic atoms of different materials are experimentally obtained and MDR'S are observed. Preliminary results of unspecific binding of biomolecules are presented. Elastic light scattering spectra of MDR's for biosensor applications are calculated numerically for biomolecules such as Bovine Serum Albumin (BSA) and for Deoxyribo Nucleic Acid (DNA).Publication Open Access Correlation between the mechanical and histological properties of liver tissue(Elsevier, 2014) Department of Mechanical Engineering; Başdoğan, Çağatay; Yarpuzlu, Berkay; Ayyıldız, Mehmet; Tok, Olgu Enis; Aktaş, Ranan Gülhan; Faculty Member; Master Student; Faculty Member; Department of Mechanical Engineering; College of Engineering; School of Medicine; 125489; N/A; N/A; N/A; N/AIn order to gain further insight into the mechanisms of tissue damage during the progression of liver diseases as well as the liver preservation for transplantation, an improved understanding of the relation between the mechanical and histological properties of liver is necessary. We suggest that this relation can only be established truly if the changes in the states of those properties are investigated dynamically as a function of post mortem time. In this regard, we first perform mechanical characterization experiments on three bovine livers to investigate the changes in gross mechanical properties (stiffness, viscosity, and fracture toughness) for the preservation periods of 5, 11, 17, 29, 41 and 53 h after harvesting. Then, the histological examination is performed on the samples taken from the same livers to investigate the changes in apoptotic cell count, collagen accumulation, sinusoidal dilatation, and glycogen deposition as a function of the same preservation periods. Finally, the correlation between the mechanical and histological properties is investigated via the Spearman's Rank-Order Correlation method. The results of our study show that stiffness, viscosity, and fracture toughness of bovine liver increase as the preservation period is increased. These macroscopic changes are very strongly correlated with the increase in collagen accumulation and decrease in deposited glycogen level at the microscopic level. Also, we observe that the largest changes in mechanical and histological properties occur after the first 11-17 h of preservation. (C) 2013 Elsevier Ltd. All rights reserved.Publication Restricted Design of functional materials via emulsion templating energy and biomedical applications(Koç University, 2017) Aydın, Derya; Kızılel, Seda; 0000-0001-9092-2698; Koç University Graduate School of Sciences and Engineering; Chemical and Biological Engineering; 28376Publication Restricted Design, fabrication and characterization of biodegradable scaffolds for tissue engineering and regenerative medicine applications(Koç University, 2018) Nazeer, Muhammad Anwaar; Yılgör, İskender; 0000-0002-7756-4192; Koç University Graduate School of Sciences and Engineering; Bio-Medical Sciences and Engineering; 24181Publication Restricted Design, fabrication and characterization of light-responsive functionalized hydrogel for tissue engineering applications(Koç University, 2021) Batool, Syeda Rubab; Kızılel, Seda; 0000-0001-9092-2698; Koç University Graduate School of Sciences and Engineering; Bio-Medical Sciences and Engineering; 28376Publication Restricted Development of anthropomorphic prosthetic hand and its control scheme for transhumeral amputees(Koç University, 2017) Shams, Sarmad; Lazoğlu, İsmail; 0000-0002-8316-9623; Koç University Graduate School of Sciences and Engineering; Bio-Medical Sciences and Engineering; 179391Publication Open Access Estimation of fracture toughness of liver tissue: experiments and validation(Elsevier, 2012) Department of Mechanical Engineering; Gökgöl, Can; Başdoğan, Çağatay; Canadinç, Demircan; Faculty Member; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489; 23433The mechanical interaction between the surgical tools and the target soft tissue is mainly dictated by the fracture toughness of the tissue in several medical procedures, such as catheter insertion, robotic-guided needle placement, suturing, cutting or tearing, and biopsy. Despite the numerous experimental works on the fracture toughness of hard biomaterials, such as bone and dentin, only a very limited number of studies have focused on soft tissues, where the results do not show any consistency mainly due to the negligence of the puncturing/cutting tool geometry. In order to address this issue, we performed needle insertion experiments on 3 bovine livers with 4 custom-made needles having different diameters. A unique value for fracture toughness (J = 164 +/- 6 J/m(2)) was obtained for the bovine liver by fitting a line to the toughness values estimated from the set of insertion experiments. In order to validate the experimental results, a finite element model of the bovine liver was developed and its hyper-viscoelastic material properties were estimated through an inverse solution based on static indentation and ramp- and-hold experiments. Then, needle insertion into the model was simulated utilizing an energy-based fracture mechanics approach. The insertion forces estimated from the FE simulations show an excellent agreement with those acquired from the physical experiments for all needle geometries. (c) 2011 IPEM. Published by Elsevier Ltd. All rights reserved.Publication Restricted Fluid flow in cardiovascular devices and surgical pathways(Koç University, 2021) Rasooli, Reza; Pekkan, Kerem; 0000-0001-7637-4445; Koç University Graduate School of Sciences and Engineering; Mechanical Engineering; 161845Publication Open Access Haemodynamic recovery properties of the torsioned testicular Artery Lumen(Nature Publishing Group (NPG), 2017) Göktaş, Selda; Pişkin, Şenol; Çapraz, Can T.; Çakmak, Yusuf O.; N/A; Department of Mechanical Engineering; Yalçın, Özlem; Ermek, Erhan; Pekkan, Kerem; Other; Faculty Member; Department of Mechanical Engineering; School of Medicine; College of Engineering; 218440; 109991; 161845Testicular artery torsion (twisting) is one such severe vascular condition that leads spermatic cord injury. In this study, we investigate the recovery response of a torsioned ram testicular artery in an isolated organ-culture flow loop with clinically relevant twisting modes (90°, 180°, 270° and 360° angles). Quantitative optical coherence tomography technique was employed to track changes in the lumen diameter, wall thickness and the three-dimensional shape of the vessel in the physiological pressure range (10–50 mmHg). As a control, pressure-flow characteristics of the untwisted arteries were studied when subjected to augmented blood flow conditions with physiological flow rates up to 36 ml/min. Both twist and C-shaped buckling modes were observed. Acute increase in pressure levels opened the narrowed lumen of the twisted arteries noninvasively at all twist angles (at ∼22 mmHg and ∼35 mmHg for 360°-twisted vessels during static and dynamic flow experiments, respectively). The association between the twist-opening flow rate and the vessel diameter was greatly influenced by the initial twist angle. The biomechanical characteristics of the normal (untwisted) and torsioned testicular arteries supported the utilization of blood flow augmentation as an effective therapeutic approach to modulate the vessel lumen and recover organ reperfusion.