We have developed a novel, microfabricated, stand-alone microfluidic device that can efficiently sort and concentrate (bio-)analyte molecules by using kinesin motors and microtubules as a chemo-mechanical transduction machine. The device removes hundreds of targeted molecules per second from an analyte stream by translocating functionalized microtubules with kinesin across the stream and concentrating them at a horseshoe-shaped collector. Target biomolecule concentrations increase up to three orders of magnitude within one hour of operation.