Miniaturized Dynamic Light Scattering Instrumentation for Use in Microfluidic Applications
Thomas Q. Chastek, Kathryn L. Beers, Eric J. Amis
Five designs for a miniaturized dynamic light scattering (DLS) instrument with microfluidic flow and fiber optic probes directly embedded into the sample are described. These instruments accurately determine the size of 10 nm to 100 nm particles dispersed in organic and aqueous solvents with most sample sizes less than 150 L. Small stir bars were incorporated directly into the instruments, and enabled blending of two different solutions immediately prior to DLS measurements. Demonstration of the instruments capabilities include high throughput measurements of the micelle to unimer transition for poly(styrene-b-isoprene) in mixed toluene/hexadecane solvent, obtained by systematically blending toluene-rich and hexadecane-rich polymer solutions. The critical solvent composition was quickly identified with less than 20 mg of polymer. Further capabilities include temperature control, demonstrated by identification of a critical micelle temperature of poly(ethylene oxide-b-propylene oxide-b-ethylene oxide), as well as multiangle DLS measurements.