Sessile Liquid Features as Molds for Silicone Elastomers

Area of Science:

• Materials Science
• Surface Chemistry
• Microfabrication

Background:

• Chemically patterned substrates with liquids form 3D contoured surfaces.
• These surfaces can serve as molds for polymer imprinting via resin curing.
• Reproducibility depends on substrate chemistry, liquid properties, and curing conditions.

Purpose of the Study:

• Investigate liquid-based molding for polymer imprinting.
• Evaluate different liquids (water, glycerol, ethylene glycol oligomer, ionic liquid) for mold fabrication.
• Assess factors influencing mold shape and imprinting success, focusing on silicone elastomer curing.

Main Methods:

• Fabrication of patterned substrates with fluoroalkylsilyl monolayers.
• Application of various liquids (water, glycerol, ethylene glycol oligomer, ionic liquid) to create sessile drops.
• Room temperature platinum(0)-catalyzed curing of Sylgard 184 silicone elastomer against the liquid molds.
• Analysis of liquid properties (vapor pressure, permeability, compatibility) and their impact on curing and feature shape.
• Demonstration of shape control using condensation/evaporation with glycerol.

Main Results:

• Water's vapor pressure and permeability in silicone were problematic but controllable via humidity.
• An ionic liquid inhibited silicone curing but offered low vapor pressure for scalable coating studies.
• An ethylene glycol oligomer showed compatibility and diffusion into the silicone.
• Glycerol demonstrated excellent control, enabling shape adjustment through condensation/evaporation.

Conclusions:

• Liquid-based molding offers a flexible and reproducible method for polymer microstructuring.
• Liquid properties significantly influence mold performance and imprinting outcomes.
• Glycerol is a promising liquid for controlled shape-morphing molds in microfabrication.