Flow focusing is a fundamental prior step in order to sort, analyze and detect particles or cells. In traditional flow-cytometry flow focusing is achieved by hydrodynamic focusing. An additional sheath fluid is used in order to confine the sample one. The main drawback of the method is the need of at least two inlets, one for the sheath and one for the sample fluid. This adds a big limitation: it is difficult to realize a device with multiple parallel micro-channels, and therefore exploit one of the main advantages introduced by microfluidic technology. As a matter of fact, the possibility of having more channels working simultaneously helps with the clogging problems, and at the same time improves the throughput. In this work we propose a parallelized microfluidic device that allows getting hydrodynamic focusing by needing of only one inlet. This is achieved by introducing a cross-filter region at each micro-channel.