Control of evaporating complex fluids through electrowetting

Evaporating drops of complex fluids such as colloidal suspensions and macromolecular solutions typically leave behind ring-shaped solid residues commonly known as coffee stains. Electrowetting-driven microfluidic flows allow for controlling this process. We present coffee stain suppression for colloidal suspensions of variable concentration and particle size and we demonstrate an improved sample preparation method for MALDI mass spectrometry.