Droplet transport on flat chemically heterogeneous surfaces via periodic wetting barriers and vibration

We report on a Flat Surface Ratchet, capable of achieving droplet transport using curved hydrophilic rungs patterned onto a hydrophobic surface. These periodic asymmetric wetting barriers can be fabricated easily on a wide variety of surfaces. Transport of a 10 ¿l droplet is achieved by an electromagnetic speaker with vertical sinusoidal vibrational amplitudes as low as 37 ¿m at 82 Hz, making this technology implementable for a wide range of discrete microfluidic applications.