Bioengineering / Biyomühendislik
Permanent URI for this collectionhttps://hdl.handle.net/11147/4529
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Conference Paper 3d Printing-Assisted Fabrication of Microfluidic Pneumatic Valves(IEEE, 2023) Keleş, Şeyda; Karakuzu, Betül; Tekin, Hüseyin CumhurPneumatic valves have a crucial place in the fluidic control in microfluidic systems. Pneumatic valves containing polydimethylsiloxane (PDMS) membrane structures are used in microfluidic systems such as cell separation, and cell manipulation due to their flexible structure, and ease of production. This study demonstrates the rapid and straightforward fabrication of pneumatic valve structures using PDMS membranes, achieved through the utilization of 3D-printed molds. As a result of our experiments, we observed valve closure in a fluidic channel with a height of 150 μm. This closure was achieved by utilizing 400 μm × 800 μm PDMS membrane with a thickness of 66 μm positioned between the fluidic and control channels, while applying 1.5 bar of pressure to the control channel. When the pressure is removed, the opening time of the valve is only 0.02 s, and this response time allows rapid valving function. The presented valve fabrication strategy would allow easy and low-cost production of sophisticated microfluidic chips. © 2023 IEEE.Conference Object Citation - WoS: 1Citation - Scopus: 3Microfluidic Platform for Sorting Materials Based on Their Densities Using Magnetic Levitation(Institute of Electrical and Electronics Engineers Inc., 2019) Yılmaz, Esra; Özçivici, Engin; Tekin, Hüseyin CumhurCirculating Tumor Cells (CTCs) play a vital role in cancer diagnosis, prognosis and personalized medicine. However, CTCs are extremely rare in blood (i.e., down to 1-100 CTC per 1 mL human blood) and hard to isolate because of the heterogeneity of CTCs in biomarker expression. The current CTC separation and identification techniques use numerous differences between cells such as size, electric charges, density and expression of cell surface markers. However, these techniques have many limitations in terms of laborious sample preparation steps, inconsistent results caused by low specificity and efficiency and high cost. Hence, there is no standard method for isolating CTCs yet. With this study, it was aimed to fill the gap in CTC isolation and identification by proposing to develop a new method based on magnetic levitation principle, which has recently been demonstrated as a highly acceptable method for biological characterization of cells and monitoring of their cellular events. In this study, we have developed a new label-free microfluidic sorter to separate microparticles/cells based on their densities using magnetic levitation principle. Two different density microparticles (1.02 g/mL and 1.09 g/ mL) have been sorted and quantified in a continuous flow using a set of permanent magnets located in a 3D printed structure surrounding the microfluidic channel. This device can be used for rapid, low cost and label-free in-vitro diagnosis of cancer by sorting CTCs from whole blood in a high-Throughput manner. The sorted cells might further be used for downstream analysis for personalized and precision medicine. © 2019 IEEE.