SUPLEMENTARY INFORMATION Acoustic Suppression of the Coffee-Ring Effect

Experimental methods Preparation of the IDT. The IDT device was fabricated as described previously [1, 2], employing standard photolithography. The device consisted of gold interdigitated electrodes, with a pitch d=350 µm, and width w=175 µm on a 128 o Y-cut X-propagating 3 inch LiNbO 3 wafer, patterned using lift-off process. The aperture of the device was 20 mm. The resonance frequency of the IDT depends on the separation between two adjacent electrode fingers, d and the sound velocity on the LiNbO 3 wafer, c=3990 m/s. The frequency is given as f = c/(d/2). The frequencies generated by the IDT were characterized using a series network analyzer (Agilent Technologies E5071C ENA). Preparation of the superstrate. We used glass, gold and steel surfaces as the superstrates. Standard microscope glass slides with thickness 1 mm were used in most of the experiments, unless otherwise specified. When indicated in the text, glass slides were treated in oxygen plasma for 10 seconds at 50 W power to make them more hydrophilic (resulting in an equilibrium contact angle of 12+/-2 •). The Au surfaces were made by coating 100 nm gold layer by evaporation on 0.5 mm thick < 100 > Si wafer. A 20 nm Ti layer was deposited beforehand for adhesion. Superstrates were diced in 25 mm x 25 mm pieces. MALDI target plates were used as the steel superstrate. The superstrates were washed in acetone, ethanol, rinsed in deionized water and blow-dried with nitrogen before the measurements. The superstrates were characterized by measuring the contact angle and the contact angle hysteresis of water (EasyDrop, KRUSS GmBH, Germany) (see Fig. S1).