Drop Manipulation Methods

•      Asymmetric horizontal vibration

Mettu, S. & Chaudhury, M.K. Motion of Liquid Drops on Surfaces Induced by Asymmetric Vibration: Role of Contact Angle Hysteresis. Langmuir 27, 10327-10333 (2011).

–     Vibrating a drop back and forth with different amplitude induces its motion toward direction with larger substrate displacement.

 

•      Surfaces with gradient wetting properties

Langley, K.R. & Sharp, J.S. Microtextured Surfaces with Gradient Wetting Properties. Langmuir 26, 18349-18356 (2010).

–     Patterned surfaces with microwrinkled surface structures were prepared by thermally evaporating thin aluminum (10 - 300 nm thick) (Al) layers onto thick prestrained layers of a silicone elastomer.

–     On this textured surface, sessile water droplets were found to have different contact angles depending upon their position.

–     Droplets under vibration tend to move down the wetting gradient from regions of high to low interfacial energy. (larger contact angle side)

 

•      External electric field

Shi, L.T., Jiang, C.G., Ma, G.J. & Wu, C.W. Electric field assisted manipulation of microdroplets on a superhydrophobic surface. Biomicrofluidics 4, 041101 (2010).

–     Droplets were first picked up onto a hydrophilic needle, transported from one location to another, and finally released under the action of an electric field force.