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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only Stuck in a whirlpool? The role of hope and despair in dealing with risks during Afghan migration journeys(OXFORD UNIV PRESS, 2024) Van Heelsum, Anja; Graduate School of Social Sciences and HumanitiesMigration journeys are full of risk, navigated not just by physical obstacles but also by emotional tides. This study explores how the fluctuation of hope and despair plays a role in dealing with risks. Drawing upon in-depth interviews with Afghans in Turkey, this paper demonstrates that hope and despair fluctuate along migration journeys contingent upon three elements: (1) empirical evidence about the future, (2) (un)certainty and potential in the future, and (3) the agency or capability to act. The research finds that hope arises when the future is perceived as uncertain, offering individuals alternative pathways and restoring a sense of agency by transforming uncertainty into potentiality. Conversely, despair sets in when individuals perceive their near future as certain, devoid of alternatives. This sense of certainty about the near future leaves migrants feeling trapped, akin to being stuck in a whirlpool.Publication Metadata only Migration aspirations in relation to border closures, employment opportunities and risk-taking attitudes: lessons from an online survey experiment(Routledge Journals; Taylor and Francis, 2024) Elçi, Ezgi; Department of International Relations; Önay, Ayşen Ezgi Üstübici; Department of International Relations; College of Administrative Sciences and Economics; Graduate School of Social Sciences and HumanitiesThis article investigates the effect of structural and individual factors on migration aspirations in a secondary migration context. Through an online survey experiment conducted with Syrian migrants (N = 551) living in Turkey, we unpack factors explaining aspirations to stay and move onward from the current country of residence. The findings indicate that open borders alone do not compel migrants to move onward. Instead, employment opportunities in their current residence play a crucial role in shaping aspirations to stay put. Moreover, individuals inclined to take risks are more likely to migrate, even when strict border controls are in place. By highlighting the question of what motivates migrants to stay as well as to move onward, this research emphasizes individual differences in forming migration aspirations and contributes to migration aspirations literature in the secondary migration context.Publication Metadata only Robotic radical prostatectomy for prostate cancer in renal transplant recipients: results from a multicenter series(Elsevier, 2022) Marra, Giancarlo; Agnello, Marco; Giordano, Andrea; Soria, Francesco; Oderda, Marco; Dariane, Charles; Timsit, Marc-Olivier; Branchereau, Julien; Hedli, Oussama; Mesnard, Benoit; Olsburgh, Jonathon; Kulkarni, Meghana; Kasivisvanathan, Veeru; Breda, Alberto; Biancone, Luigi; Gontero, Paolo; Tilki, Derya; School of Medicine; Koç University HospitalBackground: Despite an expected increase in prostate cancer (PCa) incidence in the renal transplant recipient (RTR) population in the near future, robot-assisted radical prostatectomy (RARP) in these patients has been poorly detailed. It is not well understood whether results are comparable to RARP in the non-RTR setting. Objective: To describe the surgical technique for RARP in RTR and report results from our multi-institutional experience. Design, setting, and participants: This was a retrospective review of the experience of four referral centers. Surgical procedure: Transperitoneal RARP with pelvic lymph node dissection in selected patients. Measurements: We measured patient, PCa, and graft baseline features; intraoperative and postoperative parameters; complications, (Clavien classification); and oncological and functional outcomes. Results and limitations: We included 41 men. The median age, American Society of Anesthesiologists score, preoperative renal function, and prostate-specific antigen were 60 yr (interquartile range [IQR] 57-64), 2 points (IQR 2-3), 45 ml/min (IQR 30-62), and 6.5 ng/ml (IQR 5.2-10.2), respectively. Four men (9.8%) had a biopsy Gleason score >7. The majority of the patients (70.7%) did not undergo lymphadenectomy. The median operating time, hospital stay, and catheterization time were 201 min (IQR 170-250), 4 d (IQR 2-6), and 10 d (IQR 7-13), respectively. At final pathology, 11 men had extraprostatic extension and seven had positive surgical margins. At median follow-up of 42 mo (IQR 24-65), four men had biochemical recurrence, including one case of local PCa persistence and one local recurrence. No metastases were recorded while two patients died from non-PCa-related causes. Continence was preserved in 86.1% (p not applicable) and erections in 64.7% (p = 0.0633) of those who were continent/potent before the procedure. Renal function remained unchanged (p = 0.08). No intraoperative complications and one major (Clavien 3a) complication were recorded. Conclusions: RARP in RTR is safe and feasible. Overall, operative, oncological, and functional outcomes are comparable to those described for the non-RTR setting, with graft injury remaining undescribed. Further research is needed to confirm our findings. Patient summary: Robot-assisted removal of the prostate is safe and feasible in patients who have a kidney transplant. Cancer control, urinary and sexual function results, and surgical complications seem to be similar to those for patients without a transplant, but further research is needed.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 Micro- and nanofabrication of dynamic hydrogels with multichannel information(Nature Research, 2023) Zhang, Mingchao; Lee, Yohan; Zheng, Zhiqiang; Khan, Muhammad Turab Ali; Lyu, Xianglong; Byun, Junghwan; Giessen, Harald; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineCreating micro/nanostructures containing multi-channel information within responsive hydrogels presents exciting opportunities for dynamically changing functionalities. However, fabricating these structures is immensely challenging due to the soft and dynamic nature of hydrogels, often resulting in unintended structural deformations or destruction. Here, we demonstrate that dehydrated hydrogels, treated by a programmable femtosecond laser, can allow for a robust fabrication of micro/nanostructures. The dehydration enhances the rigidity of the hydrogels and temporarily locks the dynamic behaviours, significantly promoting their structural integrity during the fabrication process. By utilizing versatile dosage domains of the femtosecond laser, we create micro-grooves on the hydrogel surface through the use of a high-dosage mode, while also altering the fluorescent intensity within the rest of the non-ablated areas via a low-dosage laser. In this way, we rationally design a pixel unit containing three-channel information: structural color, polarization state, and fluorescent intensity, and encode three complex image information sets into these channels. Distinct images at the same location were simultaneously printed onto the hydrogel, which can be observed individually under different imaging modes without cross-talk. Notably, the recovered dynamic responsiveness of the hydrogel enables a multi-information-encoded surface that can sequentially display different information as the temperature changes.Publication Metadata only Hydrogel muscles powering reconfigurable micro-metastructures with wide-spectrum programmability(Nature Portfolio, 2023) Zhang, Mingchao; Pal, Aniket; Zheng, Zhiqiang; Gardi, Gaurav; Yildiz, Erdost; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineStimuli-responsive geometric transformations endow metamaterials with dynamic properties and functionalities. However, using existing transformation mechanisms to program a single geometry to transform into diverse final configurations remains challenging, imposing crucial design restrictions on achieving versatile functionalities. Here, we present a programmable strategy for wide-spectrum reconfigurable micro-metastructures using linearly responsive transparent hydrogels as artificial muscles. Actuated by the hydrogel, the transformation of micro-metastructures arises from the collaborative buckling of their building blocks. Rationally designing the three-dimensional printing parameters and geometry features of the metastructures enables their locally isotropic or anisotropic deformation, allowing controllable wide-spectrum pattern transformation with programmable chirality and optical anisotropy. This reconfiguration mechanism can be applied to various materials with a wide range of mechanical properties. Our strategy enables a thermally reconfigurable printed metalattice with pixel-by-pixel mapping of different printing powers and angles for displaying or hiding complex information, providing opportunities for encryption, miniature robotics, photonics and phononics applications. It is difficult to program a single stimuli-responsive geometry to transform into diverse final configurations in a systematic manner. Here, linearly responsive transparent hydrogels are developed to create micro-metastructures with wide-spectrum thermal reconfigurability.Publication Metadata only Pangolin-inspired untethered magnetic robot for on-demand biomedical heating applications(Nature Portfolio, 2023) Soon, Ren Hao; Yin, Zhen; Dogan, Metin Alp; Dogan, Nihal Olcay; Tiryaki, Mehmet Efe; Karacakol, Alp Can; Aydin, Asli; Esmaeili-Dokht, Pouria; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineUntethered magnetic miniature soft robots capable of accessing hard-to-reach regions can enable safe, disruptive, and minimally invasive medical procedures. However, the soft body limits the integration of non-magnetic external stimuli sources on the robot, thereby restricting the functionalities of such robots. One such functionality is localised heat generation, which requires solid metallic materials for increased efficiency. Yet, using these materials compromises the compliance and safety of using soft robots. To overcome these competing requirements, we propose a pangolin-inspired bi-layered soft robot design. We show that the reported design achieves heating > 70 degrees C at large distances > 5cm within a short period of time <30s, allowing users to realise on-demand localised heating in tandem with shape-morphing capabilities. We demonstrate advanced robotic functionalities, such as selective cargo release, in situ demagnetisation, hyperthermia and mitigation of bleeding, on tissue phantoms and ex vivo tissues. Untethered soft robots developed to date display limited functionalities beyond locomotion and cargo delivery. Here, the authors present a pangolin-inspired robotic design which enables heating >70 degrees C at distances > 5cm without compromising their compliance, for biomedical applications.Publication Metadata only Actuation-enhanced multifunctional sensing and information recognition by magnetic artificial cilia arrays(National Academy of Sciences, 2023) Han, Jie; Dong, Xiaoguan; Yin, Zhen; Zhang, Shuaizhong; Li, Meng; Zheng, Zhiqiang; Ugurlu, Musab Cagri; Jiang, Weitao; Liu, Hongzhong; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineArtificial cilia integrating both actuation and sensing functions allow simultaneously sensing environmental properties and manipulating fluids in situ, which are promising for environment monitoring and fluidic applications. However, existing artificial cilia have limited ability to sense environmental cues in fluid flows that have versatile information encoded. This limits their potential to work in complex and dynamic fluid-filled environments. Here, we propose a generic actuation- enhanced sensing mechanism to sense complex environmental cues through the active interaction between artificial cilia and the surrounding fluidic environments. The proposed mechanism is based on fluid-cilia interaction by integrating soft robotic artificial cilia with flexible sen-sors. With a machine learning-based approach, complex environmental cues such as liquid viscosity, environment boundaries, and distributed fluid flows of a wide range of velocities can be sensed, which is beyond the capability of existing artificial cilia. As a proof of concept, we implement this mechanism on magnetically actuated cilia with integrated laser- induced graphene-based sensors and demonstrate sensing fluid apparent viscosity, environment boundaries, and fluid flow speed with a reconfigur-able sensitivity and range. The same principle could be potentially applied to other soft robotic systems integrating other actuation and sensing modalities for diverse environmental and fluidic applications.Publication Metadata only Programmable mechanical devices through magnetically tunable bistable elements(National Academy of Sciences, 2023) Pal, Aniket; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineMechanical instabilities, especially in the form of bistable and multistable mechanisms, have recently garnered a lot of interest as a mode of improving the capabilities and increasing the functionalities of soft robots, structures, and soft mechanical systems in general. Although bistable mechanisms have shown high tunability through the variation of their material and design variables, they lack the option of modifying their attributes dynamically during operation. Here, we propose a facile approach to overcome this limitation by dispersing magnetically active microparticles throughout the structure of bistable elements and using an external magnetic field to tune their responses. We experimentally demonstrate and numerically verify the predictable and deterministic control of the response of different types of bistable elements under varying magnetic fields. Additionally, we show how this approach can be used to induce bistability in intrinsically monostable structures simply by placing them in a controlled magnetic field. Furthermore, we show the application of this strategy in precisely controlling the features (e.g., velocity and direction) of transition waves propagating in a multista-ble lattice created by cascading a chain of individual bistable elements. Moreover, we can implement active elements like a transistor (gate controlled by magnetic fields) or magnetically reconfigurable functional elements like binary logic gates for processing mechanical signals. This strategy serves to provide programming and tuning capabilities required to allow more extensive utilization of mechanical instabilities in soft systems with potential functions such as soft robotic locomotion, sensing and triggering ele-ments, mechanical computation, and reconfigurable devices.Publication Metadata only Design and build of small-scale magnetic soft-bodied robots with multimodal locomotion(Nature Portfolio, 2023) Ren, Ziyu; Department of Mechanical Engineering; Sitti, Metin; Department of Mechanical Engineering; College of Engineering; School of MedicineSmall-scale magnetic soft-bodied robots can be designed to operate based on different locomotion modes to navigate and function inside unstructured, confined and varying environments. These soft millirobots may be useful for medical applications where the robots are tasked with moving inside the human body. Here we cover the entire process of developing small-scale magnetic soft-bodied millirobots with multimodal locomotion capability, including robot design, material preparation, robot fabrication, locomotion control and locomotion optimization. We describe in detail the design, fabrication and control of a sheet-shaped soft millirobot with 12 different locomotion modes for traversing different terrains, an ephyra jellyfish-inspired soft millirobot that can manipulate objects in liquids through various swimming modes, a larval zebrafish-inspired soft millirobot that can adjust its body stiffness for efficient propulsion in different swimming speeds and a dual stimuli-responsive sheet-shaped soft millirobot that can switch its locomotion modes automatically by responding to changes in the environmental temperature. The procedure is aimed at users with basic expertise in soft robot development. The procedure requires from a few days to several weeks to complete, depending on the degree of characterization required. The protocol describes a sheet-shaped millirobot with 12 locomotion modes for traversing different terrains, a jellyfish-inspired millirobot for manipulating objects in liquids, a zebrafish-inspired millirobot for efficient swimming and a dual stimuli-responsive millirobot that can switch locomotion modes automatically by responding to the environmental temperature.Rigid-bodied robots lack deformation capabilities, limiting them to specific functions, whereas soft-bodied millibots display sophisticated locomotion strategies similar to those adopted by small-scale organisms. The detailed design and fabrication of small-scale magnetic soft-bodied robots with multimodal locomotion capability, including the processes required for locomotion control and optimization.