The walls of microfludic "smart channels" are coated by responsive mixed polymer brushes with a gradient of chemical composition. The concept of the smart channels is based on switching/adaptive behavior of the mixed polymer brushes where wetting and nonwetting can be tuned upon interaction with liquids. This design of microfluidic channels brings new opportunities for manipulating the passage of liquids in the channels. The developed approach allows us to fabricate three microfluidic elements for separation, sensing, selection, and dosing microvolumes of liquids.