A thermo-responsive polymer, poly(N-isopropylacrylamide), was used for the modification of the inner surface of a glass capillary. The modification was performed by the coupling Bind-Silane(TM) (3-acryloxypropyltrimethoxysilane) on glass surfaces and a subsequent radical polymerization of N-isopropylacrylamide and methylenebis(acrylamide) with ammonium persulfate-N,N,N',N'-tetramethylethylenediamine. A water plug placed in the capillary was successfully manipulated by warming the portion of the capillary. The movement was attributed to the wettability gradient of the inner surfaces of the polymer-modified capillary.