The present invention concerns a novel means by which liquids can be moved or mixed. Microwaves strike and heat materials that are highly susceptible to microwave heating. The susceptible materials are on, within, or near materials that melt or change shape in response to temperature increases. Upon microwave irradiation, these materials change shape (e.g., shrink or melt), causing the movement of liquids. The invention is important in many microfluidics applications, especially in biomedical analysis, where it is valuable to be able to move small volumes of liquids (e.g., on a microarray chip).