Sieves are membranes with a regular array of uniform pores that present low flow resistance. Because of such
characteristics they are promising devices for filtration, separation of particles by size and drug delivery control. If the
pore dimensions reach the scale of nanometers, new and exciting biological applications may be developed. We propose
and demonstrated a technique for fabrication of polymeric sieves using only soft lithography that allows the mass
production of sieves with pores in the scale of hundred of nanometers. The technique associates UV interference
lithography, conventional optical lithography and molding. The process starts with the UV interference lithography in a
thin SU-8 photoresist film, in order to record the small pores. After development, a thick SU-8 layer is coated, on the
previously recorded sample, in order to pattern a hexagonal sustaining structure. The structures recorded in SU-8 are
used to create a negative mold in PDMS (Polydimethylsiloxane) that is used for casting the sieve in PLLA (poly-Llactide).
Self-sustaining Nickel membranes with periodic and regular distribution of pores, in the scale of hundred of nanometers, were produced by interference lithography and electroplating. The process consists in the recording of submicrometric 2D periodic photoresist columns, on a metal-coated glass substrate, using the double exposure of an interference fringe pattern. As the photoresist is a good electrical isolator, when the sample is immersed in a Ni electroplating bath, the array of photoresist columns impedes the Nickel deposition in the patterned areas. A nickel film is then growth among the photoresist columns with a thickness up to 80 % of the height of the columns. In order to release the submicrometric
membrane from the substrate, a thick hexagonal Nickel sustaining structure is electroformed, using conventional photolithography. The dimensions of the sustaining structure can be adapted in order to fulfill the pressure requirements of the filtration system. The good uniformity of the pore sizes as well as the smooth of the surface make such devices very interesting for separation of particles by size in filtration systems.
In this paper we proposed and demonstrated the association of holographic lithography with electroforming to produce submicrometric metallic structures. To demonstrate the potential of the technique, different types of submicrometric metallic structures were generated: periodic lines, nano-tunnels and arrays of holes. Such structures can met different applications from optics to micromechanical systems.