IN SITU ELECTROKINETIC SAMPLE PREPARATION FOR SELF-ASSEMBLED MONOLAYER BASED ELECTROCHEMICAL BIOSENSING

Abstract

Electrokinetics based microfluidic systems are potentially promising for lab-on-a-chip applications due to their effectiveness in manipulating nanoscale and biological objects, label-free operation, simple fabrication processes, small voltage requirements, and most importantly simple system integration strategy. Among various electrokinetics techniques, AC electrothermal flow (ACEF) is the most promising technique in microfluidic manipulation toward biomedical applications due to its effectiveness in high conductivity biological and physiological fluids. As relatively little is known about the ACEF induced fluid motion at highly conductive samples, the characteristics of electrothermal manipulation of fluid samples with different conductivities were investigated systematically. For low conductivity sample (below 1 S/m), the characteristics of the electrothermal fluid motion was in quantitative agreement with the theory. For high conductivity samples (greater than 1 S/m), the fluid motion appeared to deviate from the model as a result of electrochemical reactions and the temperature effect. Here, a universal electrode approach which directly implements ACEF-induced sample preparation on a SAM based electrochemical sensor for point-of-care diagnostics of urinary tract infections has also been demonstrated. Using uropathogenic E. coli clinical isolates as model systems, we demonstrate that "on-chip" ACEF-induced sample preparation can improve the sensor performance without complicated system integration strategy and presents a pathway for implementing truly lab on a chip, instead of chip in a lab. Finally an integrated chip approach has been proposed for transforming electrochemical sensing system from laboratory research into point-of-care diagnostics with multiple microelectrodes.