The velocity distribution among equal-width microchannels was studied with an established equation set concerning the relationship of pressure drop and flow rate between microchannels and manifolds. The results indicated that it was feasible to achieve velocity uniformity by changing the microchannel width.A model of unequal-width microchannels was developed in this work.The microchannel widths were not equal to each other

and an optimization procedure was proposed to work out the value of each microchannel width for realizing velocity uniformity.The results showed that the optimal model might be an equal-width or unequal-width one

and the distribution of optimal microchannel widths was likely to be symmetrical or asymmetrical.The optimal model could achieve relatively ideal velocity distribution

but was hardly uniform distribution due to the errors in calculations and the selection of dimensional variables.