The fabricated microfluidic device has a channel of decreasing height, starting from 400 µm down to 25 µm in steps of 25 µm (Scheme 1a, Figure ). When a solution containing different sized particles is flown in the chip, the different height steps will sort particles according to their sizes (Scheme 1b, Figure ). This device can be used instead of filtering or centrifuging. It will filter the few particles from a large amount of liquid and sort them for easier identification. Furthermore, as the device is made of PDMS and glass, it can be used directly on a microscope to count and identify the particles. However, this device does not want to compete with more complex laboratory methodologies, like membrane filtering, sequential centrifugation and so on, but wants to be a pocket device to prescreen microparticles in water bodies.