M.S. Theses

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Browsing M.S. Theses by Subject "Actuators."

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    Design and optimization of a miniature actuator using shape memory alloy (SMA) wires
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2019., 2019.) Teymoori, Morteza.; Kocatürk, Özgür.
    Microfluidic systems have proven to be very beneficial in many fields such as chemical and biomedical sciences. The reduced sample volume, among many other advantages attracts researcher’s attention to this technology. Consequently the need for a precise fluid handling and flow control is greater than before. Although many micropump systems have been invented over the last decade, there is still a need for a small, fast, quiet, and robust pump design. Because various applications have their own specific pumping requirements, the search for application driven novel micropump designsstillcontinues. Shapememoryalloyshavebeengainingmoreattentionrecently, for their idiosyncrasies, namely shape memory effect and pseudoelasticity. The ability of the shape memory alloy to recover high deformations makes them appealing for various applications. Here we use both of its hallmark behaviors, shape memory effect andpseudoelasticity, todesignacost-effectiveandversatileelectricallydrivenactuator. To do so, we introduce a novel multistep 3D printing process for the batch fabrication of the device. For the characterization of the actuator, a conductive fluidic system was used and the obstruction level of a conductive fluid filled channel was quantified using impedance measurements of control fluid and used as an indicator of the actuation amplitude and rate. The fabricated actuator successfully closed the fluid channel even under fluid pressures of up to 150 mmHg with response time of under 100ms. This scalable design can be used in different applications such as micropump development, and microfluidic World to Chip interface.|Keywords : Shape Memory Alloys, Shape Memory Effect, Pseudoelasticity, Actuator, Micropump, Microfluidics.
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    Novel flat interface nerve electrode (FINE) design by electrically driven shape memory alloys (SMAs)
    (Thesis (M.S.)-Bogazici University. Institute of Biomedical Engineering, 2019., 2019.) Şahin, Abdülsamet.; Kocatürk, Özgür.; Güçlü, Burak.
    Flat Interface Nerve Electrodes (FINE) reshape the nerve, which results in an oval geometry and causes the fascicles to be arranged on an axis. In this way, they can provide selectivity at the fascicle level without penetrating the nerve. However, the constant pressure exerted on the nerve during the reshaping process causes nerve damage. Therefore, a dynamic design is required to apply the required force for shaping the nervewhenexcitationorreceivingsignalisnecessary. Theaimofthisstudyistodesign a dynamic FINE that can apply gradual pressure on the nerve using shape memory alloys (SMA). In this study, the actuation mechanism that will apply pressure on the nerve is provided with a SMA shaped as a spring. The main frame of the electrode was fabricated with a 3D printer. Electrode contacts were produced with chromium and gold coated with PVD technique on polyimide. The overall design performance was evaluated by a forcemeter. As a result of driving the actuator with various current values, it has been proved that it can perform gradual and controlled compression. In addition, the actuator can produce up to 0.7 N force. This demonstrates that this design can be used in the manufacture of an electrode capable of gradual compression, as well as in a system designed to cause controlled damage to the nerves.|Keywords : Shape Memory Alloy (SMA), Flat Interface Nerve Electrode (FINE), Actuator.