Elemental analysis using micro laser-induced breakdown spectroscopy (microLIBS) in a microfluidic platform.

We present here a non-labeled, elemental analysis detection technique that is suitable for microfluidic chips, and demonstrate its applicability with the sensitive detection of sodium (Na). Spectroscopy performed on small volumes of liquids can be used to provide a true representation of the composition of the isolated fluid. Performing this using low power instrumentation integrated with a microfluidic platform makes it potentially feasible to develop a portable system. For this we present a simple approach to isolating minute amounts of fluid from bulk fluid within a microfluidic chip. The chip itself contains a patterned thin film resistive element that super-heats the sample in tens of microseconds, creating a micro-bubble that extrudes a micro-droplet from the microchip. For simplicity a non-valved microchip is used here as it is highly compatible to a continuous flow-based fluidic system suitable for continuous sampling of the fluid composition. We believe such a nonlabeled detection technique within a microfluidic system has wide applicability in elemental analysis. This is the first demonstration of laser-induced breakdown spectroscopy (LIBS) as a detection technology in conjunction with microfluidics, and represents first steps towards realizing a portable lower power LIBS-based detection system.