Focusing of Alexa protein G in channels of varying widths a) Focusing in a 3 mm channel (solid line, w =3 mm – only part of the channel could be imaged) for 13s is still incomplete, while it reaches steady state in less than 9s in a 1mm device (dotted line, w =1 mm). b) Focusing in the cascaded design shows incomplete focusing after 3.4 seconds in the first stage (dotted line, w =1 mm), but is tightly focused after an additional 10.2s in the second stage (solid line spliced from each stage, w =3 mm)