Inkjet printed silver patterning on PDMS to fabricate microelectrodes for microfluidic sensing

A simple and effective metal patterning technique on polydimethylsiloxane (PDMS) using inkjet printed silver nanoparticles with a (3-mercaptopropyl) trimethoxysilane (MPTMS) adhesion promoter to form silver microelectrodes for microfluidic systems is presented. Inkjet printing is an alternative additive microfabrication technique enabling the possibility of direct metal patterning on PDMS from metal bearing liquid inks. However, the hydrophobic nature of PDMS was found to inhibit pattern formation of ink on as-fabricated substrates due to droplet coalescence. Both O₂ plasma and silane adhesion treatment were explored to overcome this limitation and were evaluated using soak testing and ultrasonication. MPTMS, applied in a two-step immersion process, was found to promote PDMS surface wettability while maintaining silver adhesion with a usable working time. The resulting printed silver patterns exhibit good compactness and continuity, and were used to fabricate three-electrode electrochemical sensors directly on PDMS successfully.