Solvent-assisted molding

When the mold is hard, for example, a silicon wafer, it is called imprint lithography [16]. Imprint lithography involves applying a very high pressure (3000 to 15 000 N cm ) for the imprinting of the mold pattern into an underlying polymer layer. Some apparent limitations [17] inherent in imprint lithography make it 

Generating Micro- and Nanopattems on Polymeric Materials. Edited by A. del Campo and E. Arzt Copyri t 2011 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-32S08-5 

In contrast, solvent-assisted molding uses an elastomeric polydimethylsiloxane (PDM S) mold in combination with an appropriate solvent instead of a rigid mold and high temperature/pressure to emboss the polymer film. The solvent, rather than temperature, softens the polymer. Solvent is either briefly applied to the PDMS mold [9] or retained in the polymer film [18] before placing the two surfaces in contact. The polymer is drawn into the cavities of the mold as solvent is removed from the mold-polymer interface by transport and evaporation. The permeable mold prevents trapping of air pockets and non-uniform solvent evaporation. After evaporation of the solvent, the mold is removed, leaving behind a relief structure complementary to its topography. 

To arrive at a condition under which soft molding can be effective, solvent absorption into the mold and evaporation from the polymer surface are modeled for their rates. If it is assumed that the rate of solvent evaporation is proportional to the solvent concentration, then one has Equation 3.1  

In soft molding, the solvent is absorbed into the mold at the interface between the polymer film and the mold. Therefore, the value of a in the soft molding would be smaller than that of a determined in a hath of solvent. Therefore, the condition 

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Solvent-Assisted Molding with a Good Solvent 47... 

Figures 3.2 and 3.3 show SEM images of several 3D structures formed by soft molding or SAMIM. The circular cones shown in Figure 3.2a have a base diameter of approximately 1 pm. Rounded triangular channels with a period of approximately 3 pm are depicted in Figure 3.2b. A three-level structure is shown in Figure 3.2c. These results demonstrate the effectiveness of solvent-assisted molding in fabricating 3D structures. SAMIM can also replicate complex relief structures over large...

In solvent-assisted molding technique, capillarity may play an important role in pulling the solution into the void spaces of the mold. When a liquid wets a capillary... 

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]. 

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