Gas flow in microchannels with bends

Bends or curves are unavoidable features in fluidic systems due to design o r technology constraints. These fluidic elements in a macrochannel always i nduce secondary flows, which result in pressure loss in addition to frictio nal loss. In this paper, this phenomenon is investigated on a microscale Wh ere flow separation is not expected to develop. A. set of microchannels, wi th the dimensions 20 x 1 x 5810 mum(3), with a 90 degrees turn at the chann el centre, has been fabricated using standard micromachining techniques. Th ree bend configurations have been tested: miter, curved and double-turn. Al l the microchannels were integrated with pressure microsensors. Argon gas w as passed through the microdevices under an inlet pressure of up to 50 psi, and the mass flow rate was measured for all the devices as a function of t he driving pressure drop. The flow rate through the channel with the miter bend, a single sharp turn at a right angle, was found to be the lowest. Pre ssure distributions along the microchannels were recorded, showing an addit ional pressure drop across the bends. The largest drop was found in the mit er bend with the lowest flow rate. The mass flow rate and pressure measurem ents indicate that secondary flow could develop in microchannels also due t o a bend, contrary to expectations.