Polymer microstructures formed by moulding in capillaries

THE formation of patterned structures on micrometre-length scales is essential for the fabrication of many electronic, optical and mechanical devices¹. Patterning technologies are well established for semiconductors and metals, but are relatively undeveloped for organic polymers (with the notable exception of the specialized polymers used in photolithography¹). Polymeric replicas of some structures have been formed by filling them with monomers which are subsequently polymerized^2á¤-5. But these procedures have important limitations, in that the usually involve the destruction of the template structure, or the resulting structures are not sufficiently regular for most applications. Here we describe a general moulding procedure which does not suffer from these limitations. For the mould we use the continuous network of channels formed when a substrate and a patterned elastomeric master are placed in intimate contact. A low-viscosity polymer precursor is placed in contact with the network, which then fills spontaneously by capillary action. After cross-linking the precursor, the master is removed (and can be reused), leaving a patterned polymer layer; depending on the choice of substrate, patterned free-standing films can be similarly produced.