We present a novel chemical sensor based on electroosmotic flow (EOF) for the simple detection of chemical adsorption in an aqueous solution. Fundamental investigations for the optimization of a microfabricated electroosmotic pump (EOP) revealed the relationship between the applied electric condition and pumping performance of EOPs. The optimized EOP had an improved minimum driving voltage of only 9 V, which could be driven with a portable battery. The EOP after surface modification by molecular imprinting, such as a method with ionic complexes, changed the pumping performance by the adsorption of chemicals on its surface. We also investigated the relationship between the change in pumping rate and the chemical species of adsorbate using quaternary ammonium cations with different alkyl chains. The pump showed a change in pumping performance depending on the length of the alkyl chains.