Inkjet-printed microelectrodes on PDMS as biosensors for functionalized microfluidic systems

Microfluidic systems based on polydimethylsiloxane (PDMS) have gained popularity in recent years. However, microelectrode patterning on PDMS to form biosensors in microchannels remains a worldwide technical issue due to the hydrophobicity of PDMS and its weak adhesion to metals. In this study, an additive technique using inkjet-printed silver nanoparticles to form microelectrodes on PDMS is presented. (3-Mercaptopropyl) trimethoxysilane (MPTMS) was used to modify the surface of PDMS to improve its surface wettability and its adhesion to silver. The modified surface of PDMS is rendered relatively hydrophilic, which is beneficial for the silver droplets to disperse and thus effectively avoids the coalescence of adjacent droplets. Additionally, a multilevel matrix deposition (MMD) method is used to further avoid the coalescence and yield a homogeneous pattern on the MPTMS-modified PDMS. A surface wettability comparison and an adhesion test were conducted. The resulting silver pattern exhibited good uniformity, conductivity and excellent adhesion to PDMS. A three-electrode electrochemical biosensor was fabricated successfully using this method and sealed in a PDMS microchannel, forming a lab-on-a-chip glucose biosensing system.