Poly stamp fabrication

Patterning SAMs in the plane of the monolayer is useful in determining the two-dimensional distribution of chemical and physical properties on a surface. There are several methods available for generation of patterned SAMs. (jlCP is a convenient technique that stamps a pattern of SAM directly on a surface (Figure 8) [82,83]. In p,CP, an elastomeric poly(dimethylsiloxane) (PDMS) stamp — fabricated by casting and curing PDMS against masters that present patterned... 

Fabrication of patterned magnetite films by soft lithography and thermal decomposition using Fe(acac)3 is also possible as described by Yang and coworkers . The modality to obtain such structures on gold substrates is illustrated in Scheme 8. The array size could be tuned by changing the dimension of patterns on poly(drmethylsiloxane) stamps, the concentration of Fe(acac)3 solution and the size of water droplets during the condensation process. 

The principles of capillary force lithography [72,73] and a representative pattern of poly(ferrocenylmethylphenylsilane) (PFMPS) stripes on Si obtained by this technique, are shown in Fig. 8. A PDMS mold was placed in contact with a thin PFMPS film (thickness 27 nm) and, subsequently, the temperature was raised above the Tg (74 °C) of the polymer. The polymer, initially confined in a thin film, is squeezed out from areas of contact between stamp and substrate. It diffuses into the grooves where structures are formed along the vertical walls of the stamp due to capillary rise. Polymer structmes, which are approximately 110 nm high and 500 nm wide, were fabricated. Section analysis of the AFM height images revealed a meniscus of the capillary rise (note the different scales for the vertical and horizontal directions). The structmes were developed by CF4/O2-RIE. After resist removal, a patterned substrate as shown earUer in Fig. 2 was obtained. 

The BF approach can be also used to fabricate hierarchical multiscale structures in the micrometer and/or submicrometer scale. For this purpose, different alternatives have been proposed. For instance, Lu and Ge [76] obtained hexagonal-patterned porous surfaces by mixing inuniscible homopolymers (ie, RS and RV) in which the pores are filled at the bottom. Whereas RS forms the wall of the pores due to its hydrophobicity, RVR is deposited within the pore based on the higher hydrophilicity. To induce an additional order, the authors embossed the films using a ROMS (poly(dimethyl siloxane)) stamp producing hierarchical pores with well-defined multiscale features. 

The stamp used in pCP is most commonly fabricated by photolithographic procedures. An image is transferred into a film of photoresist, the exposed resist is developed to produce a three-dimensional structure, and this structure is then covered with the prepolymer from which the stamp is to be formed (typically poly(dimethylsiloxane), PDMS). The PDMS is allowed to cure, and then peeled from the master. 

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