Fabrication of Microlens Arrays by Utilizing Magnetic Hydrodynamic Instability of Ferrofluid Droplets

This study proposes an actively controllable method for fabrication of polymer microlens arrays. Hexagonal arrays of ferrofluid droplets, which were utilized as the mother-mold masters for microlens molding, were generated by inducing the magnetic hydrodynamic instability under different magnetic fields. To fabricate numerous cavity molds for microlens array molding, we used the field-dependent shapes of the ferrofluid droplets to create different sized molds. For the fabricated microlens arrays, their field-dependent bottom areas, lens height, radii of curvature, and the fill-factor were discussed. Furthermore, performances of the microlenses, including the numerical aperture, focal length, and depth of field, were tested.