First, an array of parallel platinum wires are formed in a master mold that is created using electron beam lithography.
In addition, many reports including the above two are for PDMS filling into protruded features (e.g., an array of pillar) in the master mold that is easier when the pillars are well separated than filling into (recessed) holes.
However, besides its low Young's modulus, it is found challenging to fill uncured PDMS into the nanoscale pattern on the master mold that is coated with an anti-adhesion monolayer needed for clean demolding.
However, for nanoscale patterns, it is challenging to fill uncured PDMS into the holes or trenches on the master mold that is coated with a silane anti-adhesion layer needed for clean demolding.
We treated the master mold surface (that was already coated with a silane anti-adhesion monolayer) with toluene or hexane, and found that the filling by undiluted PMDS into the nanoscale holes on the master mold was improved despite the high viscosity of the undiluted PDMS.
We, here, studied the effect of solvent treatment of the master mold surface (that was already coated with a silane anti-adhesion monolayer) on PDMS filling into nanoscale holes on the master mold.
Poly(dimethylsiloxane) (PDMS) production molds are then created using the master molds through elastomer molding.
To study the effect of the additional solvent treatment of the silane-coated master mold on PDMS molding, right before (undiluted) PDMS casting, some master molds were dipped into toluene or hexane for 1 min and dried with nitrogen gun. Figure 1 shows the scanning electron microscopy (SEM) image of the master mold consisting of array of holes with various diameters.
This technique may greatly simplify the design and fabrication of master molds, provide more flexibility to widely used soft lithography process, and also reduce the damage to the master by using PDMS negative mold as the working mold.
Silicon master molds were generated by the Canadian Microsystems Consortium (http://www.cmc.ca/).
