Browsing by Subject "Microdroplets"

Now showing 1 - 5 of 5

Open Access
Label-free sensing in microdroplet-based microfluidic systems
(MDPI Multidisciplinary Digital Publishing Institute, 2018) Kalantarifard, A.; Saateh, A.; Elbuken, Çağlar
Droplet microfluidic systems have evolved as fluidic platforms that use much less sample volume and provide high throughput for biochemical analysis compared to conventional microfluidic devices. The variety of droplet fluidic applications triggered several detection techniques to be applied for analysis of droplets. In this review, we focus on label-free droplet detection techniques that were adapted to various droplet microfluidic platforms. We provide a classification of most commonly used droplet platform technologies. Then we discuss the examples of various label-free droplet detection schemes implemented for these platforms. While providing the research landscape for label-free droplet detection methods, we aim to highlight the strengths and shortcomings of each droplet platform so that a more targeted approach can be taken by researchers when selecting a droplet platform and a detection scheme for any given application.
Open Access
Microfluidic droplet content detection using integrated capacitive sensors
(Elsevier, 2015-04) Isgor, P. K.; Marcali, M.; Keser, M.; Elbuken, C.
Microfluidic capacitive sensors have been used for detection of droplets, however they have been lacking the sensitivity required for detecting the content of droplets. In this study, we developed a scalable, portable, robust and high sensitivity capacitive microdroplet content detection system using coplanar electrodes with nanometer thick silicon dioxide (SiO2) passivation layer and off-the-shelf capacitive sensors. The microfluidic chip we have designed provides easy and rapid modification of droplet content by mixing two aqueous liquids at any given ratio. The change in dielectric constant of the droplet content leads to the change in capacitive signal. The dielectric content of droplets was modified continuously while corresponding capacitance signal was measured. The resolution of the system was measured as 3 dielectric permittivity units. The results were verified using a semiconductor parameter analyzer. The application specific integrated circuit used in this work enables a portable, low-cost detection system and matches the performance of bench-top analyzers. Automated and precise measurement of dielectric content in droplets for biochemical assay monitoring is a major application of the presented system.
Open Access
A microfluidic droplet system for ultra-monodisperse droplet generation: A universal approach
(Elsevier Ltd, 2022-07-22) Kalantarifard, Ali; Alizadeh-Haghighi, Elnaz; Elbüken, Çağlar
Despite the importance of droplet monodispersity, a universal methodology for high monodispersity droplet generation does not exist yet. We have recently demonstrated that unlike the conventional method of droplet generation, applying an identical pressure from a single source makes the microfluidic droplet system immune to the external fluctuations that originate from the imperfection of the flow source. In this work, we show that our method is universal and applicable to other common microfluidic devices and flow sources. We applied this method to flow-focusing and coflow devices that are commonly used for high-frequency microdroplet generation. In addition to the pressure pump, we used a syringe pump to show that our method is applicable to flow rate controllable systems as well. We compared the monodispersity of droplets formed by the conventional methods and the novel method explained in this work. © 2022 The Authors
Open Access
Real-time image-based droplet measurement
(Chemical and Biological Microsystems Society, 2020) Elahi, Sepehr; Kalantarifard, Ali; Kalantarifard, Fatemeh; Elbüken, Çağlar
The ability to measure physical properties of droplets in real-time is required to design precise operations on droplet-based systems. In this study, we implemented a real-time droplet tracker that tracks the positions of droplets and measures droplet generation frequency as well as droplets' physical properties, such as size, size distribution, shape, velocity, circularity. Furthermore, using the droplet length, we use curve fitting to determine the dispersed phase viscosity. Our droplet tracker is implemented in Python, using the OpenCV library and can be run on a routine PC.
Open Access
Theoretical and experimental limits of monodisperse droplet generation
(Elsevier Ltd, 2021-01-16) Ali, Kalantarifard; Elnaz, Alizadeh-Haghighi; Abtin, Saateh; Elbüken, Çağlar
Droplet microfluidic systems are becoming routine in advanced biochemical studies such as single cell gene expression, immuno profiling, precise nucleic acid quantification (dPCR) and particle synthesis. For all these applications, ensuring droplet monodispersity is critical to minimize the uncertainty due to droplet volume variation. Despite the wide usage of droplet-based microfluidic systems, the limit of monodispersity for droplet generation systems is still unknown. Here, we present an analytical approach that takes into account all the system dynamics and internal/external factors that disturb monodispersity. Interestingly, we are able to model the dynamics of a segmented two-phase flow system using a single-phase flow analogy, electron flow, in electrical circuits. We offer a unique solution and design guidelines to ensure ultra-monodisperse droplet generation. Our analytical conclusions are experimentally verified using a T-junction droplet generator. Equally importantly, we show the limiting experimental factors for reaching the theoretical maximum of monodispersity.