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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3

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Department: search.filters.department.Department of Mechanical EngineeringSubject: search.filters.subject.Chemistry, physical and theoretical

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    Electroadhesion with application to touchscreens
    (Royal Soc Chemistry, 2019) Ayyıldız, Mehmet; Persson, Bo N. J.; N/A; Department of Mechanical Engineering; Şirin, Ömer; Başdoğan, Çağatay; PhD Student; Faculty Member; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 125489
    There is growing interest in touchscreens displaying tactile feedback due to their tremendous potential in consumer electronics. In these systems, the friction between the user's fingerpad and the surface of the touchscreen is modulated to display tactile effects. One of the promising techniques used in this regard is electrostatic actuation. If, for example, an alternating voltage is applied to the conductive layer of a surface capacitive touchscreen, an attractive electrostatic force is generated between the finger and the surface, which results in an increase in frictional forces acting on the finger moving on the surface. By altering the amplitude, frequency, and waveform of this signal, a rich set of tactile effects can be generated on the touchscreen. Despite the ease of implementation and its powerful effect on our tactile sensation, the contact mechanics leading to an increase in friction due to electroadhesion has not been fully understood yet. In this paper, we present experimental results for how the friction between a finger and a touchscreen depends on the electrostatic attraction and the applied normal pressure. The dependency of the finger-touchscreen interaction on the applied voltage and on several other parameters is also investigated using a mean field theory based on multiscale contact mechanics. We present detailed theoretical analysis of how the area of real contact and the friction force depend on contact parameters, and show that it is possible to further augment the friction force, and hence the tactile feedback displayed to the user by carefully choosing those parameters.
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    Microstructure and tribological properties of titahfnbzr high entropy alloy coatings deposited on ti-6al-4v substrates
    (Elsevier Sci Ltd, 2019) Bal, Burak; N/A; Department of Mechanical Engineering; N/A; Canadinç, Demircan; Motallebzadeh, Amir; N/A; Faculty Member; Researcher; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; College of Engineering; N/A; N/A; 23433; N/A
    We report on the microstructure and tribological behavior of equimolar TiTaHfNbZr high entropy alloy (HEA) thin films deposited on the biomedical Ti-6Al-4V substrates by RF magnetron sputtering. Results of nanoindentation and sliding wear experiments were evaluated along with the microstructure and topographical information obtained from scanning electron microscopy and atomic force microscopy. The findings clearly demonstrate that the TiTaHfNbZr HEA not only forms a homogenous and dense coating mechanically compatible with the Ti-6Al-4V substrates, but also provides a significantly enhanced surface protection against wear and cracking, which could prove valuable especially in long-term orthopedic implants that bear dynamic contact loading, such as in the cases of hip or knee joints.
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    Low-cost optical assays for point-of-care diagnosis in resource-limited settings
    (Amer Chemical Soc, 2021) Jiang, Nan; Tansukawat, Natha Dean; Gonzalez-Macia, Laura; Ateş, H. Ceren; Dinçer, Can; Güder, Fırat; Yetişen, Ali K.; Department of Mechanical Engineering; Taşoğlu, Savaş; Faculty Member; Department of Mechanical Engineering; College of Engineering; 291971
    Readily deployable, low-cost point-of-care medical devices such as lateral flow assays (LFAs), microfluidic paper-based analytical devices (mu PADs), and microfluidic thread-based analytical devices (mu TADs) are urgently needed in resource-poor settings. Governed by the ASSURED criteria (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliverability) set by the World Health Organization, these reliable platforms can screen a myriad of chemical and biological analytes including viruses, bacteria, proteins, electrolytes, and narcotics. The Ebola epidemic in 2014 and the ongoing pandemic of SARS-CoV-2 have exemplified the ever-increasing importance of timely diagnostics to limit the spread of diseases. This review provides a comprehensive survey of LFAs, mu PADs, and mu TADs that can be deployed in resource-limited settings. The subsequent commercialization of these technologies will benefit the public health, especially in areas where access to healthcare is limited.