We report a lab-on-a-chip (LOC) that can separate and detect Escherichia coli (E. coli) in simulated urine samples for urinary tract infection (UTI) applications. The LOC consists of two (concentration and sensing) chambers connected in series and an integrated impedance detector. The two-chamber approach is designed to reduce the nonspecific absorption of a protein, e.g., albumin, that potentially coexists with E. coli in urine. We directly separate E. coli K-12 from cocktail urine in a concentration chamber containing microsized magnetic beads conjugated with anti-E. coli antibody. The immobilized E. coli is transferred to a sensing chamber for the impedance measurement. The measurement at the concentration chamber suffers from nonspecific absorption of albumin on the gold electrode, which may lead to false-positive response. By contrast, the measured impedance at the sensing chamber shows a ∼60-kΩ impedance change. This is a clear distinction between 6.4 × 10 4 and 6.4 × 10 5 CFU/mL, covering the threshold of UTI (10 5 CFU/mL). The sensitivity of the LOC in detecting E. coli is characterized to be at least 3.4 × 10 4 CFU/mL. We also characterized the LOC for different age groups and white blood cell spiked samples. These preliminary data show promising potential for application in portable LOC devices for UTI detection.[
2010-0263]Index Terms-Escherichia coli (E. coli), lab-on-a-chip (LOC), point-of-care testing, urinary tract infection (UTI).
Plated copper is being considered as an alternative to screenprinted silver for the front contacts of crystalline silicon solar cells. Generally, a thin nickel layer, annealed to form nickel silicide is used to improve contact resistance and adhesion of the contact to silicon. Nickel layers can also be used to prevent the detrimental diffusion of copper into the cell. One challenge to the commercialization of plated copper contacts is the potential for this nickel barrier to fail, causing catastrophic local electrical shunts of the cell. In this work, we monitor shunting during a thermal stress test to evaluate the adequacy of nickel diffusion barrier layers and identify different mechanisms by which Ni-Cu plated cells may become shunted.
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