Design and development of electrochemical polymer-based lab-on-a-disc devices for biological applications

The need for reliable, fast, easy to use, portable and cost effective analytical tools has led to several novel approaches in the development of miniaturized microfluidic platforms integrated with electrochemical sensors. This thesis presents the design and development of an electrochemical detection based centrifugal microfluidic platforms towards applications in bioprocess monitoring, medical diagnostics, food and environmental analysis, etc. Stencil based electrode fabrication approach was developed and optimized to pattern reliable and reproducible electrodes on a polymeric substrate. Also, a fast, easy to use and simplified approach was established for interfacing the electrodes integrated with the polymeric Lab-on-a-disc (LoD) devices. On-disc filtration and supported liquid membrane (SLM) extraction was adapted on LoD devices for sample pre-treatment (e.g., filtration, extraction, enrichment). The applicability of the developed microfluidic systems was demonstrated by monitoring a biological process, namely quantifying the amount of the bacterial metabolite p-Coumaric acid (pHCA) produced by genetically modified E. coli cells. The first generation LoD device (with integrated filtration) was used to quantify pHCA at the end of bacterial culture (24 hours) when the cell density is the highest. We demonstrated the efficiency of the centrifugal filtration, which enabled cell-free electrochemical detection eliminating the effect of high cell density on electrochemical quantification of pHCA. The second generation LoD device (with integrated SLM extraction) was more advanced and facilitated extraction, enrichment, as well as electrochemical detection of pHCA from the complex sample matrix, i.e., E. coli supernatant at different time points during the cell culture. Realizing the need for more advanced sensors that can be integrated with microfluidic devices, we developed dual functionality sensors facilitating surface-enhanced Raman spectroscopy (SERS) based sensing as well as electrochemical detection. Moreover, to eliminate the need for bulky peripheral instrumentation connected through slip rings for on-disc electrochemical measurements, we present a miniaturized smartphone controlled wireless potentiostat, which can be integrated on a rotating microfluidic platform.