Lithography MIMIC

Fig. 4.1. Illustration of the structure gap for an automotive three-way catalysts (TWO) depicted by a schematic drawing of a monolithic, supported catalyst. The lower right image shows a TEM picture of aged automotive catalyst 12-nm Pt on AI2O3. Note, the presence of small Pt single crystals. Well-defined model catalysts such as those made by electron-beam lithography (EBL lower middle image) are used to mimic real catalyst and bridge the gap between single crystal studies (bottom left) and real-life catalysts...

Soft lithography includes a collection of lithographic methods in which a soft mold or template is used to create patterned structures in the subjeeted materials. These methods offer attractive solutions for producing well-ordered CP nanowires. For example, Beh et al have developed a micromolding in capillaries (MIMIC) process in which a poly(dimethylsiloxane) (PDMS) mold with embedded ehannels can be used for the... 

Recently, the soft lithography [51,52] technique of micromolding in capillaries (MIMIC) [53,54] has been used to fabricate MIP micromonoliths on silicon wafers [55,56]. In MIMIC, an elastomeric stamp that possesses recessed features is placed in intimate contact with a soUd substrate. The recessed microchannels on the stamp form a network of empty capillaries. When a low-viscosity fluid precursor is placed at one end, it spontaneously fills the channels by capillary action. Curing of the fluid leaves patterned microstructures on the substrate surface as shown in Fig. 7. 

Numerous attempts to mimic the lotus effect for various applications have been made in recent years. These attempts are stimulated, on the one hand, by the development of the technology of micropatterned surfaces (such as lithography), and on the other hand, by the increasing need for nonadhesive (nonsticky) surfaces. Since the surface-to-volume ratio grows with miniaturization, the surface effects are crucial for microdevices such as microelectromechanical systems. In addition to microdevices, the lotus effect finds its application for conventional self-cleaning surfaces (paints, glasses, textiles, etc.). Possible applications for underwater devices, microfluidics, and other areas have been discussed. 

Whitesides research groups opened a new era in microfabrication and rephcation using sol-gel method. They have explored so-called soft lithography techniques such as microcontact printing (/rCP), replica molding (REM), microtransfer molding (/ TM), and micromolding in capillaries (MIMIC), which have been described in their excellent review paper in detail (Xia, 1998). 

Decades passed before it was technologically possible to mimic such nano-strncmres and fabricate artificial bionic moth eye ARS [191, 194]. Technologically, moth eyes can be produced at a correct scale using lithography, crossing three gratings at 120°. Another approach to fabrication is electron-beam etching. 

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