FABRICATION AND INTEGRATION OF 3D C-PDMS ELECTRODES IN MONOLITHIC ALL-PDMS MICROFLUIDIC DEVICE

Candidate: Said Saleh Ali Abdellatif
Supervisor: Dr. Darius Rackus

Abstract:

Electrodes in microfluidics provide a wide range of applications, particularly in electrochemical (EC) analysis. The geometrical integration of electrodes in microfluidic devices limits their range of applications. Conventional approaches that depend on 2 or 2.5 dimensional electrode integration lack the flexibility required for EC analysis in coplanar setting. On the other hand, electrode 3D integration in multiplanar setting offers a more uniform electric current along the microfluidic channel, therefore. To this day, despite many methods were introduced for 3D integration of electrodes into microchannels, they are complicated, high-cost techniques with no simple integration of electrodes in multiplanar setting that allows allocation of electrodes in different angles around each plane along the microchannel. To address this, our thesis reports a method for fabrication of 3D electrodes from conductive polymer, particularly, carbon-polydimethylsiloxane (C-PDMS). Moreover, the integration of these electrodes with microfluidic channels is achieved by exploiting differential solubilities of 3D-printed thermoplastic scaffolds. Those scaffolds were produced from two different materials, the first were dissolved to reveal channels that were filled with C-PDMS. Dissolution of the second material reveals the microchannel architecture. Firstly, single C-PDMS electrodes were fabricated and characterized for production fidelity. Electrodes were also characterized electrochemically, demonstrating diffusion control and good electron transfer kinetics. Secondly, in one step, electrodes were fabricated and integrated in 3D geometry and multiplanar setting into a PDMS microchannel device to demonstrate the potential of this fabrication method for forming monolithic devices for biosensing. Horseradish peroxidase was quantified electrochemically, as a demonstration of the potential use of such devices for biosensing applications. This thesis paves the way for a novel benchtop low-cost fabrication of electrode structures with complex 3D geometries.