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Publication Metadata only 3D bioprinted glioma models(Iop Publishing Ltd, 2022) N/A; N/A; N/A; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Yığcı, Defne; Sarabi, Misagh Rezapour; Üstün, Merve; Atçeken, Nazente; Sokullu, Emel; Önder, Tuğba Bağcı; Taşoğlu, Savaş; Undergraduate Student; PhD Student; PhD Student; Researcher; Faculty Member; Faculty Member; Faculty Member; Department of Mechanical Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); School of Medicine; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; School of Medicine; School of Medicine; College of Engineering; N/A; N/A; N/A; N/A; 163024; 184359; 291971Glioma is one of the most malignant types of cancer and most gliomas remain incurable. One of the hallmarks of glioma is its invasiveness. Furthermore, glioma cells tend to readily detach from the primary tumor and travel through the brain tissue, making complete tumor resection impossible in many cases. To expand the knowledge regarding the invasive behavior of glioma, evaluate drug resistance, and recapitulate the tumor microenvironment, various modeling strategies were proposed in the last decade, including three-dimensional (3D) biomimetic scaffold-free cultures, organ-on-chip microfluidics chips, and 3D bioprinting platforms, which allow for the investigation on patient-specific treatments. The emerging method of 3D bioprinting technology has introduced a time- and cost-efficient approach to create in vitro models that possess the structural and functional characteristics of human organs and tissues by spatially positioning cells and bioink. Here, we review emerging 3D bioprinted models developed for recapitulating the brain environment and glioma tumors, with the purpose of probing glioma cell invasion and gliomagenesis and discuss the potential use of 4D printing and machine learning applications in glioma modelling.Publication Metadata only 3D-printed micrometer-scale wireless magnetic cilia with metachronal programmability(American Association for the Advancement of Science, 2023) Zhang, Shuaizhong; Hu, Xinghao; Li, Meng; Bozüyük, Uğur; Zhang, Rongjing; Suadiye, Eylül; Han, Jie; Wang, Fan; Onck, Patrick; Department of Mechanical Engineering; Sitti, Metin; Faculty Member; Department of Mechanical Engineering; College of Engineering; 297104Biological cilia play essential roles in self-propulsion, food capture, and cell transportation by performing coordinated metachronal motions. Experimental studies to emulate the biological cilia metachronal coordination are challenging at the micrometer length scale because of current limitations in fabrication methods and materials. We report on the creation of wirelessly actuated magnetic artificial cilia with biocompatibility and metachronal programmability at the micrometer length scale. Each cilium is fabricated by direct laser printing a silk fibroin hydrogel beam affixed to a hard magnetic FePt Janus microparticle. The 3D-printed cilia show stable actuation performance, high temperature resistance, and high mechanical endurance. Programmable metachronal coordination can be achieved by programming the orientation of the identically magnetized FePt Janus microparticles, which enables the generation of versatile microfluidic patterns. Our platform offers an unprecedented solution to create bioinspired microcilia for programmable microfluidic systems, biomedical engineering, and biocompatible implants.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 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 review of bioresorbable implantable medical devices: materials, fabrication, and implementation(Wiley, 2020) N/A; N/A; Department of Mechanical Engineering; Department of Mechanical Engineering; Singh, Rahul; Bathaei, Mohammad Javad; İstif, Emin; Beker, Levent; PhD Student; PhD Student; Researcher; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 354990; 308798Implantable medical devices (IMDs) are designed to sense specific parameters or stimulate organs and have been actively used for treatment and diagnosis of various diseases. IMDs are used for long-term disease screening or treatments and cannot be considered for short-term applications since patients need to go through a surgery for retrieval of the IMD. Advances in bioresorbable materials has led to the development of transient IMDs that can be resorbed by bodily fluids and disappear after a certain period. These devices are designed to be implanted in the adjacent of the targeted tissue for predetermined times with the aim of measurement of pressure, strain, or temperature, while the bioelectronic devices stimulate certain tissues. They enable opportunities for monitoring and treatment of acute diseases. To realize such transient and miniaturized devices, researchers utilize a variety of materials, novel fabrication methods, and device design strategies. This review discusses potential bioresorbable materials for each component in an IMD followed by programmable degradation and safety standards. Then, common fabrication methods for bioresorbable materials are introduced, along with challenges. The final section provides representative examples of bioresorbable IMDs for various applications with an emphasis on materials, device functionality, and fabrication methods.Publication Metadata only A robotic indenter for minimally invasive measurement and characterization of soft tissue response(Elsevier, 2007) Avtan, Levent; Düzgün, Oktay; N/A; N/A; Department of Mechanical Engineering; Samur, Evren; Sedef, Mert; Başdoğan, Çağatay; Master Student; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering College of Engineering; 192890; N/A; 125489The lack of experimental data in current literature on material properties of soft tissues in living condition has been a significant obstacle in the development of realistic soft tissue models for virtual reality based surgical simulators used in medical training. A robotic indenter was developed for minimally invasive measurement of soft tissue properties in abdominal region during a laparoscopic surgery. Using the robotic indenter, force versus displacement and force versus time responses of pig liver under static and dynamic loading conditions were successfully measured to characterize its material properties in three consecutive steps. First, the effective elastic modulus of pig liver was estimated as 10-15 kPa from the force versus displacement data of static indentations based on the small deformation assumption. Then, the stress relaxation function, relating the variation of stress with respect to time, was determined from the force versus time response data via curve fitting. Finally, an inverse finite element solution was developed using ANSYS finite element package to estimate the optimum values of viscoelastic and nonlinear hyperelastic material properties of pig liver through iterations. The initial estimates of the material properties for the iterations were extracted from the experimental data for faster convergence of the solutions.Publication Metadata only A variable elastance-based mock circulation model for replicating human cardiovascular system(Wichtig Editore, 2011) Küçükaksu, S.; Şahin, Tuğcan; Department of Mechanical Engineering; Lazoğlu, İsmail; Faculty Member; Department of Mechanical Engineering; College of Engineering; 179391N/APublication Metadata only A virtual reality toolkit for path planning and manipulation at nano-scale(IEEE Computer Soc, 2006) N/A; N/A; Department of Mechanical Engineering; Varol, Aydın; Günev, İhsan; Başdoğan, Çağatay; Master Student; Master Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 125489A virtual reality (VR) toolkit that integrates the human operator into a virtual environment by means of visual and haptic feedback has been developed to design and test manipulation strategies at nano-scale. Currently, the toolkit is capable of modeling the mechanistic interactions between an AFM tip and spherical particles on a substrate surface and generating optimum manipulation paths using a potential field approach. In addition, haptic fixtures were designed to guide the user to follow the calculated paths.Publication Metadata only An exploration of plastic deformation dependence of cell viability and adhesion in metallic implant materials(Elsevier, 2016) Gerstein, G.; Maier, H. J.; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; Uzer, Benay; Toker, Sıdıka Mine; Cingöz, Ahmet; Önder, Tuğba Bağcı; Canadinç, Demircan; Researcher; PhD Student; Researcher; Faculty Member; Faculty Member; Department of Mechanical Engineering; N/A; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; School of Medicine; College of Engineering; N/A; 255504; N/A; 184359; 23433The relationship between cell viability and adhesion behavior, and micro-deformation mechanisms was investigated on austenitic 316L stainless steel samples, which were subjected to different amounts of plastic strains (5%, 15%, 25%, 35% and 60%) to promote a variety in the slip and twin activities in the microstructure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) revealed that cells most favored the samples with the largest plastic deformation, such that they spread more and formed significant filopodial extensions. Specifically, brain tumor cells seeded on the 35% deformed samples exhibited the best adhesion performance, where a significant slip activity was prevalent, accompanied by considerable slip-twin interactions. Furthermore, maximum viability was exhibited by the cells seeded on the 60% deformed samples, which were particularly designed in a specific geometry that could endure greater strain values. Overall, the current findings open a new venue for the production of metallic implants with enhanced biocompatibility, such that the adhesion and viability of the cells surrounding an implant can be optimized by tailoring the surface relief of the material, which is dictated by the micro-deformation mechanism activities facilitated by plastic deformation imposed by machining.Publication Metadata only Application of the finite element method in spinal implant design and manufacture(Woodhead Publ Ltd, 2012) N/A; Department of Mechanical Engineering; Zafarparandeh, Iman; Lazoğlu, İsmail; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 179391This chapter reviews the application of the finite element (FE) method in designing and manufacturing spinal implants. The structure of the chapter is built upon the procedure of creating the FE model for the human spine, which consists of establishing the FE model for each component of the spine, including mesh generation and material property, verification, validation and, finally, implant design process. Each part of the spine FE model is discussed from the simulation point of view and available models are introduced. For the implant design, some examples are chosen from the literature, which are also being used widely in the medical industry.