An apparatus and method is disclosed for forming a nano structure on a substrate with nano particles. The method is characterized in that a coating liquid for a surface layer which includes a solvent including a hydrophilic solvent and a hydrophobic solvent and a polymer compound soluble in the hydrophobic solvent is used; the hydrophilic solvent has a boiling point equal to or higher than that of the hydrophobic solvent; the hydrophilic solvent has a dipole moment of 0 or more and less than 2. The mass flow measuring device may also measure the density andor volumetric flow of the mixed liquid. The controller may modify operation of the shredder in response to the detected vibrations having a predetermined characteristic. The handle can assume a plurality of stable positions corresponding to different handle heights from a surface on which the wheels rest, hence enabling the child to grip the handle with the correct posture at different stages of its growth.