Çankaya GCRIS Standart veritabanının içerik oluşturulması ve kurulumu Research Ecosystems (https://www.researchecosystems.com) tarafından devam etmektedir. Bu süreçte gördüğünüz verilerde eksikler olabilir.

Makine Mühendisliği Bölümü

Permanent URI for this communityhttps://hdl.handle.net/20.500.12416/19

Browse

Browsing Makine Mühendisliği Bölümü by Department "Çankaya Üniversitesi, Mühendislik Fakültesi, Makine Mühendisliği"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Article
    Investigation on replication of microfluidic channels by hot embossing
    (Taylor&Francis, 2017) Çoğun, Ferah; Yıldırım, Ender; Arikan, M. A. Sahir; 31835
    In this study, effects of embossing temperature, time, and force on production of a microfluidic device were investigated. Polymethyl methacrylate (PMMA) substrates were hot embossed by using a micromilled aluminum mold. The process parameters were altered to observe the variation of replication rate in width and depth as well as symmetry of the replicated microfluidic channels. Analysis of variance (ANOVA) on the experimental results indicated that embossing temperature was the most important process parameter, whereas embossing time and force have less impact. One distinguishing aspect of this study is that, the channels were observed to be skewed to either side of the channel depending on the location of the protrusions on the mold. The mechanism of the skewness was investigated by finite element analysis and discussed in detail. Results showed that the skewness depends on the flow characteristics of the material and could be reduced by increasing the embossing temperature. The best replication rates were obtained at parameter settings of 115 degrees C, 10kN, and 8min for the molds with minimum 56 mu m wide features of 120 mu m depth. We also showed that the fabricated channels could be successfully sealed by solvent-assisted thermo-compressive bonding at 85 degrees C under 5.5kN force.
  • Thumbnail Image
    Article
    Modeling and analysis of a microfluidic capillary valve
    (Gazi Univ, 2017) Yıldırım, Ender; 31835
    Here, a numerical model for analysis of a capillary valve for use in microfluidic devices was presented. Capillary valves are preferred especially in passive microfluidic systems, where the capillary forces dominate the liquid motion, to manipulate the flow. The capillary valve in this work, was formed by the sudden expansion of a rectangular microchannel to an opening, whose depth and width are larger than the height and the width of the channel respectively. Noting that there was no available analytical model to determine the pressure capacity of such valves, a numerical model based on energy minimization was utilized. Free software Surface Evolver was used to solve the model. Dependence of the pressure capacity on the contact angle of the working liquid on the channel material was investigated. It was found that the pressure capacity of the valves would be maximum if the contact angle on all surfaces is 90 degrees. Accordingly, the valves could withstand approximately 2.5 kPa for 100 mu m x 100 mu m channels when the contact angle was 90 degrees. The model was verified by comparing the results with those available in the literature.