Makine Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/263

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Citation - Scopus: 1
A Droplet Based Multi-Drug Screening System Controlled With Electrostatic Microvalves
(Chemical and Biological Microsystems Society, 2012) Yildirim, E.; Yıldırım, Ender; Özgür, E.; Külah, H.; 31835; Makine Mühendisliği
This paper presents a droplet-based drug effect analysis system utilizing electrostatically-actuated normallyclosed microvalves to screen the effect of multiple drugs on a single type of cell. Proposed system minimizes the need for off-chip equipment by utilizing parylene based electrostatic microvalves. Prototypes of the system were fabricated and tested using colored DI water and 3 μm diameter micro beads, emulating drugs and cells respectively. During the tests, micro beads could be successfully entrapped in 137 pl droplets. Tests carried out with yeast cells also yielded successful encapsulation of the cells. It was shown that, switching between the drugs could be achieved by applying 200 V dc to operate the microvalves.
Citation - WoS: 7
Citation - Scopus: 8
A novel zero-dead-volume sample loading interface for microfluidic devices: flexible hydraulic reservoir (FHR)
(Iop Publishing Ltd, 2018) Hatipoglu, Utku; Yıldırım, Ender; Cetin, Barbaros; Yildirim, Ender; 158278; 31835; Makine Mühendisliği
Infusing minute amounts of valuable liquids such as samples to microfluidic chips by using common pumping schemes such as syringe pumps often result in an excessive dead-volume. We present a simple yet effective sample loading interface, which helps by pumping the sample to the chip by using the hydraulic pressure generated by the syringe pump. Results show that sample volumes as low as 25 mu l can be delivered at flow rates ranging between 10-30 mu l min(-1). Maximum dead volume ratio was observed to be 3% when infusing 200 mu l of sample at 10 mu l min(-1).
Citation - Scopus: 1
An Electrostatically Actuated Parylene Microvalve for Lab-On-A-Chip Applications
(2011) Yildirim, E.; Yıldırım, Ender; Kulah, H.; Arikan, M.A.S.; 31835; Makine Mühendisliği
This paper presents a novel electrostatic microvalve to control in-plane flow on parylene based lab-on-a-chip-devices. Normally-closed design of the microvalve insulates the working fluid from the electric field, while providing low leakage up to 40 kPa inlet pressure. Prototypes are fabricated and tested for pull-in and flow characterization. Pull-in voltage is measured to be 150 V independent of the working fluid. No leakage is detected up to 20 kPa inlet pressure. © 2011 IEEE.
Citation - WoS: 12
Analysis and characterization of an electrostatically actuated in-plane parylene microvalve
(Iop Publishing Ltd, 2011) Yildirim, E.; Yıldırım, Ender; Kulah, H.; 31835; 120121; Makine Mühendisliği
This paper presents analysis and implementation of a simple electrostatic microvalve designed for use in parylene-based lab-on-a-chip devices. The microvalve utilizes an in-plane collapsing diaphragm. To investigate the pull-in behavior of the diaphragm and flow characteristics, a thorough analysis is carried out using the finite element method. Microvalves with different diaphragm radii are fabricated using surface micromachining techniques. Pull-in tests are carried out under the no-flow condition with air, oil and water as the working fluid. Test results show that the pull-in occurs around 20 V for 450 mu m radius diaphragms with oil and air. However, it is not possible to observe pull-in up to 100 V (both ac and dc) for the case of water as the working fluid, due to its relatively high dielectric constant and conductivity. The flow tests show that no leakage flow was observed up to 4 kPa inlet pressure under 85 V actuation potential. The leakage ratio becomes 17% at 10 kPa inlet pressure. It is observed that the leakage can be reduced controllably by increasing the actuation potential, enabling the precise control of the flow rate.
Citation - WoS: 5
Citation - Scopus: 5
Analysis and testing of a contraction-and-expansion micromixer for micromilled microfluidics
(Springer Heidelberg, 2017) Yildirim, Ender; Yıldırım, Ender; 31835; Makine Mühendisliği
In this paper, numerical analysis and experimental investigation of a micromixer, which was specifically designed for microfluidic devices fabricated by micromilling, is presented. The mixer is composed of series of contractions and expansions in zigzag arrangement along a mixing channel. Mixers, fabricated by micromilling on polymethylmethacrylate (PMMA), were tested with %0.1 Ponceau 4R red food dye solution and distilled water. According to experiment results, over 70% mixing efficiency could be obtained for the flows with Reynolds number (Re) greater than 40. It was also numerically shown that by increasing the number of successive contractions and expansions, it could be possible to achieve over 80% mixing efficiency when Re = 55 for the species with diffusion coefficient of 5 x 10(-9) m(2)/s. Although the micromixer was specifically designed for micromilling, it is expected that the mixer can be useful in any microfluidic device fabricated by any other technique.
Citation - WoS: 0
Citation - Scopus: 0
Fluorescent on-chip imager by using a tunable absorption filter
(Ieee, 2017) Arpali, Caglar; Yıldırım, Ender; Yildirim, Ender; Arpali, Serap Altay; 20809; 31835; 51304; Makine Mühendisliği
Citation - WoS: 6
Citation - Scopus: 10
Implementation and characterization of an absorption filter for on-chip fluorescent imaging
(Elsevier Science Sa, 2017) Yildirim, Ender; Yıldırım, Ender; Arpali, Caglar; Arpali, Serap Altay; 31835; 20809; 51304; Makine Mühendisliği
Here we present fabrication and characterization of an absorption filter with superior roll-on properties and precisely tunable cut-off wavelengths for fluorescent imaging applications in lab-on-a-chip systems. The filters were fabricated by spinning dye doped photopolymer (Orasol Yellow in Norland Optical Adhesive 60) on glass substrates. The fabrication technique allowed us to precisely tune the cut-off wavelength of the filters. We showed that filters with different cut-off in the range of 386 nm-504 nm could be obtained simply by controlling the settling time before spinning. The filters exhibited a steep roll-on from stopband to passband at the cut-off. Transmission in the stopband was observed to be maximum 3% while it was almost constant at 100% in the passband within the range of 220 nm-620 nm. On-chip use of the filters was also demonstrated for imaging particular fluorescent beads. (C) 2016 Elsevier B.V. All rights reserved.
Citation - WoS: 27
Citation - Scopus: 30
Investigation on replication of microfluidic channels by hot embossing
(Taylor & Francis inc, 2017) Çoğun, Ferah; Cogun, Ferah; Yildirim, Ender; Yıldırım, Ender; Arikan, M. A. Sahir; 31835; Makine Mühendisliği
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.
MEMS Malzeme karakterizasyonu için bütünleşik bir elektrostatik mikro bükülme test yapısı tasarımı ve gerçekleştirilmesi
(Çankaya Üniversitesi, 2012) Yıldırım, Ender; Akın, Tayfun; Arıkan, M. A. Sahir; 31835; 104090; 163987; Makine Mühendisliği
Mikro elektromekanik sistemlerde kullanılan malzemelerin mekanik özelliklerinin, üretim yöntemleri nedeniyle, mikro boyuttaki test yapılarıyla tespit edilmesi gerekmektedir. Bu çalışmada, eyleyici, test numunesi ve ölçüm skalası tek bir yonga üzerinde bütünleşik olarak üretilmiş bir mikro bükülme test yapısı sunulmaktadır. Tüm bileşenlerin bütünleşik olarak üretilmiş olması, benzer sistemlerde gözlenen hizalama problemini ortadan kaldırmaktadır. Yapı, iki uçtan ankastre mesnetli bir test kirişinin orta noktasından tarak tipi bir elektrostatik eyleyici ile çekilmesi esasına dayanmaktadır. Bükülme miktarı, ölçüm skalası üzerinden, görüntü işleme yöntemleri kullanılarak tespit edilmektedir. Tasarlanan yapılar yalıtkan-üzeri-silisyum pullar kullanılarak üretilmiştir. Testler sonucunda, literatürde belirtilen sonuçlarla uyumlu olarak, silisyum elastik modülü 136 GPa olarak belirlenmiştir
Citation - WoS: 22
Citation - Scopus: 21
Phaseguide assisted liquid lamination for magnetic particle-based assays
(Royal Soc Chemistry, 2014) Phurimsak, Chayakom; Yıldırım, Ender; Yildirim, Ender; Tarn, Mark D.; Trietsch, Sebastiaan J.; Hankemeier, Thomas; Pamme, Nicole; Vulto, Paul; 31835; Makine Mühendisliği
We have developed a magnetic particle-based assay platform in which functionalised magnetic particles are transferred sequentially through laminated volumes of reagents and washing buffers. Lamination of aqueous liquids is achieved via the use of phaseguide technology; microstructures that control the advancing air-liquid interface of solutions as they enter a microfluidic chamber. This allows manual filling of the device, eliminating the need for external pumping systems, and preparation of the system requires only a few minutes. Here, we apply the platform to two on-chip strategies: (i) a one-step streptavidin-biotin binding assay, and (ii) a two-step C-reactive protein immunoassay. With these, we demonstrate how condensing multiple reaction and washing processes into a single step significantly reduces procedural times, with both assay procedures requiring less than 8 seconds.
Citation - WoS: 26
Citation - Scopus: 30
Phaseguides as tunable passive microvalves for liquid routing in complex microfluidic networks
(Royal Soc Chemistry, 2014) Yildirim, Ender; Yıldırım, Ender; Trietsch, Sebastiaan J.; Joore, Jos; van den Berg, Albert; Hankemeier, Thomas; Vulto, Paul; 31835; Makine Mühendisliği
A microfluidic passive valving platform is introduced that has full control over the stability of each valve. The concept is based on phaseguides, which are small ridges at the bottom of a channel acting as pinning barriers. It is shown that the angle between the phaseguide and the channel sidewall is a measure of the stability of the phaseguide. The relationship between the phaseguide-wall angle and the stability is characterized numerically, analytically and experimentally. Liquid routing is enabled by using multiple phaseguide with different stability values. This is demonstrated by filling complex chamber matrices. As an ultimate demonstration of control, a 400-chamber network is used as a pixel array. It is the first time that differential stability is demonstrated in the realm of passive valving. It ultimately enables microfluidic devices for massive data generation in a low-cost disposable format.

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