Fabrication of three-dimensional microstructures by soft molding

We have developed soft molding as a method for meso-scale-area fabrication of three-dimensional structures. The soft molding, which is a form of soft lithography, involves placing an elastomeric mold on the surface of a spin-coated polymer film with a slight pressure (<1 ${\mathrm{N/cm}}^2\mathrm{),}$ allowing the mold to absorb solvent, releasing the pressure, and then letting the mold and the substrate remain undisturbed for a period of time. The three-dimensional structure thus formed is robust in that the pattern fidelity is preserved without any distortion or defects. For the soft molding to be successful, the rate of solvent absorption by the mold should be larger than the rate of solvent evaporation. The method is demonstrated with several three-dimensional structures.