Microfluidic chips in the last two decades have had significant advances in the analysis of interfacial tension phenomenon due to their many advantages. To analyze interfacial tension phenomena, droplet flow in microchannels can be used. In this study, water-n-hexane interfacial tension in the presence of surface-active agents was measured, using microfluidic tensiometry. For this purpose, a glass microfluidic flow-focusing junction was fabricated for generating n-hexane droplets within an aqueous phase. The dependence of droplet size on the concentration of surfactants has been investigated. A theoretical equation was developed, considering force balance on the droplet generation in the microfluidic device, giving a relation between the interfacial tension and the generated droplet sizes. By standardizing the microfluidic chips with the aid of a system, whose interfacial tension is known (hexane normal and tween 20 in distilled water), interfacial tension can be measured with measuring the size of produced droplets for other systems that can form droplets in the microchannel. In this study, the microfluidic device and the relation were employed to measure the interfacial tension in the presence of either of sodium dodecyl sulphate (SDS) or Cetyl trimethylammonium bromide (CTAB) surfactants. It was found that the measured interfacial tensions deviate less than 10% compared to those measured with a commercially available ring method.

In this study, the continuous separation of hexane and water in micro-systems was investigated. For this purpose, two dimensional glass microfluidic chips were fabricated using laser ablation and thermal bonding method. The chips comprised of a main microchannel and few lateral micro channels. It was aimed to exit hexane and water from the, respectively, main and lateral micro channels. It was found that decreasing the width and increasing the number of the lateral micro channels, and increasing the flow rate of water result in increased separation. Also, increasing the flow rate of hexane and increasing the length of the lateral micro channels result in the reduction of the separation. In order to increase the operating flow rate of the capillary separation, three-dimensional microfluidic chips were fabricated by parallelization of four microscale capillary separators. With the three-dimensional microfluidic chips, the separation efficiency of up to 60% was achieved at the operating flow rate of 1. 5 mL min-1.

Because of the importance of biomolecule extraction and its genetic investigations in the medical and forensic field with all the limitations such as sensitivity, nature of work, high cost, the need for highly skilled technicians, automation and portability of the system in terms of detection with existing technologies, several need not fulfilled. There is a need to integrate sample preparation and detection methods. To overcome these limitations, nowadays most studies have focused on improving detection technologies, and accordingly, advances in detection technologies MICROFLUIDICS is one of the best systems with convincing feautures. Other advantages of this technology including the extraction of DNA and protein which is involved automation in a sample preparation, the ability to operate in small sample sizes as well as minimizing the consumption, cost, and processing time of solvents.