For the preparation of mono-dispersed mixed metal oxide micro hollow spheres, homogeneous precipitation was carried out using a mixed metal sulfate precursor solution and an IPA (isopropyl alcohol) solvent in a micro precipitator configured with a micro capillary tip and a millimeter scale glass tube. The prepared micro particles revealed the morphology of hollow spheres with a narrow size distribution. For the preparation of uniform micro hollow particles without agglomeration the micro precipitator had to be operated in a laminar flow region with a low Reynolds number. The size of the particle could be controlled simply by changing the capillary tip diameter and/or the line velocity of the precursor solution and the IPA solvent. Also, the shell thickness of the hollow spheres could be controlled just by the concentration of the precursor solution. The mass production of micro hollow spheres by the micro fluidic device was validated in a micro precipitator inserted with multi-capillary tubes. (c) 2005 Elsevier B.V. All rights reserved.