Thermally responsive phospholipid preparations for fluid steering and separation in microfluidics.

Aqueous phospholipid preparations comprised of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) are prevalent materials for biological characterization and become gel-like near physiological temperature, but have a low viscosity below 24°C. The rheology of 20% phospholipid preparations of [DMPC]/[DHPC] = 2.5 reveals that, under conditions utilized for fluid steering, the materials are shear-thinning power-law fluids with a power-law index ranging from 0.30 through 0.90. Phospholipid preparations are utilized to steer fluids in microfluidic chips and support hydrodynamic delivery of sample across a double T injection region in a chip. The fact that the phospholipids are fully integrated as a valving material as well as a separation medium is demonstrated through the separation of linear oligosaccharides labeled with 1-aminopyrene-3,6,8-trisulfonic acid.