Experimental Study of Foam Generation in a Microfluidic Device

Small scale tests can be conducted using Lab-on-a-chip devices with very tiny amount of fluids. In the case that the fluid is in the gas phase, it should be carried inside a bubble. In this paper, this type of bubbles is generated with certain size in a flow focusing microfluidic device. Microfluidic device can be manufactured by SOFT LITHOGRAPHY. when the bubble density is high enough in a channel, they come in to contact, and they flow in the form of crystal foam. the flow of the foams in the channel depends on the liquid flow rate and inlet gas pressure. This shall determine dynamic behaviors of the flow such as super-stability. Two types of foam including wet and dry foams are generated in flow focusing device. At certain pressure of 600 to 700 (mbar), the foam behavior is switched to non-linear behavior in which the shape of bubble is changed in period of time. At specific flow rate of 0.1 and 0.2 (ml/hr), it is observed that bubbles are generated in one raw and some others are in two within channel which are called hex-one and hex-two. The effects of increasing the flow rate at constant pressure (which reduces the size of the bubble from dry foam to wet foam) and the effects of increasing the pressure in the constant flow rate (which increases the size of the bubble from wet foam to dry foam) are investigated.