Microtransfer molding

X.-M. Zhao, Y. Xia and G.M. Whitesides, Fabrication of three-dimensional micro-structmes Microtransfer molding, Adv. Mater., 8 (1996) 837. 

Microtransfer Molding (p-TM) A PDMS stamp is filled with a prepolymer or ceramic precursor and placed on a substrate. The material is cured and the stamp is removed. The technique is able to create multilayer systems and features as small as 250 nm. 

Metal/semiconductor, 19-2, 19-4—19-10 Metal-containing polythiophenes, 13-33-13-37 Metal-insulator transition (MIT), 16-2 Metallic box model, 15-65-15-66 Metallic islands, 16-2, 16-5, 16-9, 16-17 Metal-oxide-semiconductor FETs, 8-77 Metal-polyaniline composite, 7-26 in-situ metathesis reaction, 7-29 Meta-substituted polyanilines, 7-36-7-38 Microcontact printing, 8-56, 8-58 p, CP, 9-28-9-27 of rr-PATs, 9-28-9-30 Microdisk lasers, 22-56, 22-57-22-61 Micro-fibers, 16-3, 16-5, 16-11-16-12 Micromolding in capillaries (MIMIC), 9-27 Microring laser, 22-21, 22-54-22-57 Microscopic cracks, 9-24 Microtransfer molding (p TM), 9-28-9-27 Microwave electrochromism, 20-49-20-50 Miller—Abrahams theory, 2-4-2-5, 2-19 MM and DD calculations, 1-24 Mobility edge (Ec), 15-8, 15-20, 15-42 Mobility, 2-2-2-3, 2-5, 2-9, 2-17, 2-19, 9-24-9-26, 9-33-9-34... 

The relief parts of the PDMS stamp can also be used to transfer patterns. In this approach, the PDMS stamp is first filled with a polymer precursor and then pressed against the substrate. After curing (solidifying) the polymer, the PDMS stamp is removed and a pattern matching its relief parts remains on the substrate. This process is called microtransfer molding. Many other processes implement similar concepts. 

Figure 4.72. Schematic of soft lithographic procedures for (a) replica molding (REM), (b) microtransfer molding (pTM), (c) micromolding in capillaries (MIMIC), and (d) solvent-assisted micromolding (SAMIM). Reproduced with permission from Angew. Chem. Int. Ed. 1998, 37, 550. Copyright 1998 Wiley-VCH.

Figure 26-12. Schematic of (a) microtransfer molding (fiTM) and, (b) micromolding in capillaries (MIMIC) techniques used to develop sol/gel micro-patterns onglass surfaces, [(a) Kim et aL,J. Am. Chem. Soc. 1996 118 572-573. Reproduced by permission of The American Chemical Society, (b) from Zhcu> etal.,J. Mater. Chem. 1997 7 1069-1074. Reproduced by permission of The Royal Society of Chemistry.]...

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). 

Zhao G., Tohge N., Nishii J. Fabrication and characterization of diffraction gratings using photosensitive Al203gel films. Jpn. J. Appl. Phys. 1998 37 1842-1846 Zhao X.-M., Xia Y., Whitesides G.M. Fabrication of three-dimensional micro-stmctures microtransfer molding. Adv. Mater. 1996 8 837-840... 

The soft elastomeric stamp can be used either as a vehicle for biomolecular surface patterning (an application called microcontact printing (p.CP)) or to create three dimensional reliefs, particularly on polymer materials, as in micromolding in capillaries (MIMIC), microtransfer molding (pTM) or solvent-assisted molding. These techniques have been successfully applied in the fabrication of polymer patterns with dimensions down to the sub-100 nm scale and will be described in this chapter. These patterns have found many relevant applications in the life sciences, where scientists often need to spatially control topographical and chemical properties of surfaces at small scales [1, 5, 6]. 

In order to overcome MIMIC limitations, some authors have proposed the use of a closely related technique that is called microtransfer molding (pTM)(Figure 4.5b). In this case, a drop of liquid pre-polymer is poured over the patterned surface ofa PDMS mold, thus letting the liquid fill the mold cavities. Then, the excess of pre-polymer is removed and the filled PDMS is placed on top of a substrate, where the pre-polymer solidifies inside the mold. Zhao et al. [12] have shown that is possible to fabricate structures with 100 nm in lateral dimension by this method, although a thin polymer layer remained on the substrate. This method can be adapted for creating structures on curved surfaces and for the fabrication of multilayered structures. 

Zhao, X.M., Smith, S.P., Waldman, S.J., Whitesides, G.M., and Prentiss, M. (1997) Demonstration of waveguide couplers fabricated using microtransfer molding. Appl. Phys. Lett., 71 (8), 1017-1019. 

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