Patterning colloidal suspensions by selective wetting of microcontact-printed surfaces

Micropatterns made of ceramic powders can be obtained by selective wetting of microcontact-printed surfaces. A large wetting contrast between hydrophilic micropatterns and hydrophobic areas was created. Aqeous colloidal dispersions of aluminum oxide and tin oxide adhered only to the hydrophilic micropatterns whereas they were repelled from the hydrophobic areas in a simple dip coating process. We examined two molecular ink/substrate systems: thiol self-assembled monolayers (SAM) on gold and octadecyl–trichlorosilane (OTS) SAM on silicon wafer substrates. Corresponding contact angles obtained under varying printing conditions are presented. The chemical compositions of the printed layers were characterized by ToF-SIMS mass spectrometry. The thiol–gold SAM readily forms in microcontact printing whereas the OTS layer contains a significant amount of PDMS residues. However, printing and selective wetting could be carried out successfully on both ink/substrate systems. The ceramic micropatterns obtained indicate a maximum resolution in the order of 5 μm.