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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Deep learning-augmented T-junction droplet generation(Elsevier Inc., 2024) N/A; Department of Mechanical Engineering; Ahmadpour, Abdollah; Shojaeian, Mostafa; Taşoğlu, Savaş; Department of Mechanical Engineering; KU Arçelik Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Koç Üniversitesi İş Bankası Yapay Zeka Uygulama ve Araştırma Merkezi (KUIS AI)/ Koç University İş Bank Artificial Intelligence Center (KUIS AI); Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of EngineeringDroplet generation technology has become increasingly important in a wide range of applications, including biotechnology and chemical synthesis. T-junction channels are commonly used for droplet generation due to their integration capability of a larger number of droplet generators in a compact space. In this study, a finite element analysis (FEA) approach is employed to simulate droplet production and its dynamic regimes in a T-junction configuration and collect data for post-processing analysis. Next, image analysis was performed to calculate the droplet length and determine the droplet generation regime. Furthermore, machine learning (ML) and deep learning (DL) algorithms were applied to estimate outputs through examination of input parameters within the simulation range. At the end, a graphical user interface (GUI) was developed for estimation of the droplet characteristics based on inputs, enabling the users to preselect their designs with comparable microfluidic configurations within the studied range.Publication Metadata only Optimizing porosity of the catalyst for hydrogen peroxide based thrusters(Elsevier B.V., 2024) Kokal, U.; Yıldız, Y.; Baysal, M.; Department of Mechanical Engineering; Emerce, Nur Ber; Yıldız, Utku Can; Karabeyoğlu, Mustafa Arif; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of EngineeringThe texture of the catalyst support is a crucial factor for H2O2 decomposition due to the expansion of H2O2 in monopropellant thrusters, which can lead to overpressure and catalyst breakage. Therefore, alumina supports with 5 wt%, 10 wt%, and 15 wt% microcrystalline cellulose templates were studied to create macropores. MIP and SEM analysis showed that microcrystalline cellulose template increases the macropore fraction. Low-concentration H2O2 decomposition experiments revealed that over 10 wt% microcrystalline cellulose prevented catalyst breakage. Additionally, the thermal durability of the catalyst was studied at different calcination temperatures. Alumina with 15 wt% microcrystalline cellulose and a 900 °C calcination temperature exhibited the highest fracture strength and suitable reaction kinetics. The catalysts were tested in high-concentration H2O2 monopropellant thruster. The results demonstrated enhancement in catalyst size retention, pressure stability, and pressure drop. Introducing macropores through microcrystalline cellulose addition overcomes unstable thruster performance and it extends catalyst lifespan in H2O2 monopropellant thrusters’ applications. © 2023 Elsevier B.V.Publication Metadata only Perspective on smart materials for empowering small-scale manipulation(Elsevier B.V., 2024) Zhang, Mingchao; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of EngineeringPublication Metadata only Enhanced co-design and evaluation of a collective robotic construction system for the assembly of large-scale in-plane timber structures(Elsevier B.V., 2024) Leder, Samuel; Kim, HyunGyu; Menges, Achim; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of EngineeringCollective robotic construction (CRC) is an emerging approach to construction automation based on the collaboration among teams of small mobile robots. This paper enhances an existing modular CRC system, showcasing its capability to assemble full-scale in-plane timber structures. Utilizing strategies of co-design, the robotic actuators were updated to accommodate material tolerance in the passive building material, timber struts, which they use for locomotion and assemble into structures. A custom effector was also developed to establish architecturally relevant, structural connections between struts. The enhancements address two major challenges in CRC system development: material tolerance and connections. To showcase these research findings and compare with other construction automation systems, a reinforced slab structure was assembled. With a building envelop of 0.485 m3, this is one of the largest structures assembled by a CRC system. As such, the work highlights the potential applicability of CRC in real-world architectural projects. © 2024 The Author(s)Publication Metadata only Biocorrosion behavior TiTaNbZrMo high-entropy alloy thin films sputtered on NiTi shape memory alloy substrates with controlled microstructure(Elsevier B.V., 2024) Department of Mechanical Engineering; Hosseinjany, Azizeh; Canadinç, Demircan; Yağcı, Mustafa Barış; 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; College of EngineeringThis paper presents the experimental findings on the effect of deposition conditions on the microstructure of the corrosion-resistant TiTaNbZrMo high entropy alloy (HEA) thin films deposited on NiTi substrates with the purpose of enhancing biocompatibility of the NiTi shape memory alloy (SMA). For this purpose, RF magnetron sputtering was employed to fabricate TiTaNbZrMo HEA films with 750 nm and 1500 nm thicknesses. Static immersion experiments were conducted in simulated body fluid (SBF) and artificial saliva (AS) solutions for 1, 14, and 28 days to establish the relationship between Ni ion release and deposition parameters. The results revealed that thin films grown under low working pressure exhibited crystalline body-centered cubic (BCC) microstructure with a highly dense, compact, and crack-free structure, while those deposited under high-pressure conditions exhibited an amorphous structure with inherent cracks. The biocorrosion test results indicated that the dense and compact thin film fulfilled the expected corrosion resistance requirements for prolonged utility in human body. Moreover, the HEA films revealed an outstanding amount of hydroxyapatite (HAp) formation, indicating remarkable bioactivity and favorable bone-bonding capabilities. The findings suggest that the HEA films deposited under low working pressures could constitute promising alternatives to conventional coatings on NiTi SMAs.Publication Metadata only Digital monitoring of the microchannel filling flow dynamics using a non-contactless smartphone-based nano-liter precision flow velocity meter(Elsevier Advanced Technology, 2024) Xu, Weiming; Köydemir, Hatice Ceylan; Department of Mechanical Engineering; Atik, Abdulkadir Yasin; Beker, Levent; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of EngineeringMicrofluidic systems find widespread applications in diagnostics, biological research, chemistry, and engineering studies. Among their many critical parameters, flow rate plays a pivotal role in maintaining the functionality of microfluidic systems, including droplet-based microfluidic devices and those used in cell culture. It also significantly influences microfluidic mixing processes. Although various flow rate measurement devices have been developed, the challenge remains in accurately measuring flow rates within customized channels. This paper presents the development of a 3D-printed smartphone-based flow velocity meter. The 3D-printed platform is angled at 30 degrees to achieve transparent flow visualization, and it doesn't require any external optical components such as external lenses and filters. Two LED modules integrated into the platform create a uniform illumination environment for video capture, powered directly by the smartphone. The performance of our platform, combined with a customized video processing algorithm, was assessed in three different channel types: uniform straight channels, straight channels with varying widths, and vessel-like channel patterns to demonstrate its versatility. Our device effectively measured flow velocities from 5.43 mm/s to 24.47 mm/s, with video quality at 1080p resolution and 60 frames per second, for which the measurement range can be extended by adjusting the frame rate. This flow velocity meter can be a useful analytical tool to evaluate and enhance microfluidic channel designs of various lab-on-a-chip applications.Publication Metadata only Nanotechnology-based electrochemical biosensors for monitoring breast cancer biomarkers(John Wiley and Sons Inc, 2023) Nasrollahpour, Hassan; Khalilzadeh, Balal; Hasanzadeh, Mohammad; Rahbarghazi, Reza; Estrela, Pedro; Naseri, Abdolhossein; Sillanpää, Mika; Department of Mechanical Engineering; Taşoğlu, Savaş; Department of Mechanical Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of EngineeringBreast cancer is categorized as the most widespread cancer type among women globally. On-time diagnosis can decrease the mortality rate by making the right decision in the therapy procedure. These features lead to a reduction in medication time and socioeconomic burden. The current review article provides a comprehensive assessment for breast cancer diagnosis using nanomaterials and related technologies. Growing use of the nano/biotechnology domain in terms of electrochemical nanobiosensor designing was discussed in detail. In this regard, recent advances in nanomaterial applied for amplified biosensing methodologies were assessed for breast cancer diagnosis by focusing on the advantages and disadvantages of these approaches. We also monitored designing methods, advantages, and the necessity of suitable (nano) materials from a statistical standpoint. The main objective of this review is to classify the applicable biosensors based on breast cancer biomarkers. With numerous nano-sized platforms published for breast cancer diagnosis, this review tried to collect the most suitable methodologies for detecting biomarkers and certain breast cancer cell types.Publication Metadata only Liquid metal microdroplet-initiated ultra-fast polymerization of a stimuli-responsive hydrogel composite(Wiley-V C H Verlag Gmbh, 2023) Zhang, Jianhua; Liao, Jiahe; Liu, Zemin; Zhang, Rongjing; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineRecent advances in composite hydrogels achieve material enhancement or specialized stimuli-responsive functionalities by pairing with a functional filler. Liquid metals (LM) offer a unique combination of chemical, electrical, and mechanical properties that show great potential in hydrogel composites. Polymerization of hydrogels with LM microdroplets as initiators is a particularly interesting phenomenon that remains in its early stage of development. In this work, an LM-hydrogel composite is introduced, in which LM microdroplets dispersed inside the hydrogel matrix have dual functions as a polymerization initiator for a polyacrylic acid-poly vinyl alcohol (PAA/PVA) network and, once polymerized, as passive inclusion to influence its material and stimuli-responsive characteristics. It is demonstrated that LM microdroplets enable ultra-fast polymerization in approximate to 1 min, compared to several hours by conventional polymerization techniques. The results show several mechanical enhancements to the PAA/PVA hydrogels with LM-initiated polymerization. It is found that LM ratios strongly influence stimuli-responsive behaviors in the hydrogels, including swelling and ionic bending, where higher LM ratios are found to enhance ionic actuation performance. The dual roles of LM in this composite are analyzed using the experimental characterization results. These LM-hydrogel composites, which are biocompatible, open up new opportunities in future soft robotics and biomedical applications. A composite hydrogel embedded with liquid metal (LM) microdroplets is introduced, where the LM microdroplets have dual roles of initiating ultra-fast polymerization and passive inclusion. The physical effects of LM on polymerization and stimuli-responsive behaviors are analyzed, including swelling and ionic actuation due to osmotic pressure differences. Their benefits to the LM-hydrogel functionalities, such as robot locomotion, are demonstrated.Publication Metadata only Machine learning-based shear optimal adhesive microstructures with experimental validation(Wiley-V C H Verlag Gmbh, 2023) Dayan, Cem Balda; Son, Donghoon; Aghakhani, Amirreza; Wu, Yingdan; Demir, Sinan Ozgun; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineBioinspired fibrillar structures are promising for a wide range of disruptive adhesive applications. Especially micro/nanofibrillar structures on gecko toes can have strong and controllable adhesion and shear on a wide range of surfaces with residual-free, repeatable, self-cleaning, and other unique features. Synthetic dry fibrillar adhesives inspired by such biological fibrils are optimized in different aspects to increase their performance. Previous fibril designs for shear optimization are limited by predefined standard shapes in a narrow range primarily based on human intuition, which restricts their maximum performance. This study combines the machine learning-based optimization and finite-element-method-based shear mechanics simulations to find shear-optimized fibril designs automatically. In addition, fabrication limitations are integrated into the simulations to have more experimentally relevant results. The computationally discovered shear-optimized structures are fabricated, experimentally validated, and compared with the simulations. The results show that the computed shear-optimized fibrils perform better than the predefined standard fibril designs. This design optimization method can be used in future real-world shear-based gripping or nonslip surface applications, such as robotic pick-and-place grippers, climbing robots, gloves, electronic devices, and medical and wearable devices. This study combines the machine learning-based optimization and finite-element-method-based shear mechanics simulations to find shear-optimized fibril designs automatically. The results show that the computed optimal fibrils perform better than the predefined standard fibril designs. This design optimization framework can be used in future nonslip surface applications in grippers, robots, gloves, and electronic, medical, and wearable devices.Publication Metadata only Magnetic putty as a reconfigurable, recyclable, and accessible soft robotic material(Wiley-V C H Verlag Gmbh, 2023) Li, Meng; Pal, Aniket; Byun, Junghwan; Gardi, Gaurav; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineMagnetically hard materials are widely used to build soft magnetic robots, providing large magnetic force/torque and macrodomain programmability. However, their high magnetic coercivity often presents practical challenges when attempting to reconfigure magnetization patterns, requiring a large magnetic field or heating. In this study, magnetic putty is introduced as a magnetically hard and soft material with large remanence and low coercivity. It is shown that the magnetization of magnetic putty can be easily reoriented with maximum magnitude using an external field that is only one-tenth of its coercivity. Additionally, magnetic putty is a malleable, autonomous self-healing material that can be recycled and repurposed. The authors anticipate magnetic putty could provide a versatile and accessible tool for various magnetic robotics applications for fast prototyping and explorations for research and educational purposes. Permanent magnetic particles embedded in a viscoelastic putty matrix result in a self-healing soft magnetic material with both high remanence and low coercivity, providing hard-magnetic performance without the need for inaccessible strong magnetic fields. Programmable and reconfigurable magnetization, frequency-dependent force output, and easy to shape and assemble, magnetic putty can be a versatile tool in research prototyping and inspire future explorations.