discuss how pressure influences mixing in microchannels Solu

discuss how pressure influences mixing in microchannels ?

Solution

Pressure-driven flow is commonly used in microfluidic applications.The velocity profile of such flow is typically parabolic-like across the fluid–fluid interface in a rectangular micromixer.The parabolic velocity profile could cause a substantial difference in residence time of diffusive transport between the diffusion near the top and bottom walls and in the center of the channel.The variation of diffusion with the position may influence the measurements of mixing intensity and molecular properties as well.
A microchannel which mixes fluids is called a micromixer.There are two types of mixing methods in microchannels:active and passive.In active mixing,fluid is pumped into the channel in such a way that mixing is induced,say by a time-dependent forcing.However this is difficult to do on such tiny scales as micrometres,and is also undesirable from a manufacturing standpoint because the design involves moving parts.In passive mixing,the shape of the micromixer is designed to create flow patterns that naturally mix.The average flow rate of a liquid within a micro- or nanofluidic channel is proportional to the pressure gradient imposed on both ends of the capillary.According to the Hagen–Poiseuille equation, the pressure drop in a fluid flowing through a channel is decided by the channel size (fourth power relation) and the flow rate (linear relation).The smaller channel (pressure increasing zone) will dramatically increase the pressure in the upstream channel.