It is our common experience to see water drip out of a leaky faucet in, say, a kitchen sink. While dripping in this case may be an unwanted process, it can gainfully be employed as one of the methods, among a host of different techniques, to produce drops of various liquids for useful purposes. Production of drops, of various sizes and numbers, is used in a variety of applications ranging from crop sprays to printing and patterning on different substrates. In this short write-up, brief descriptions of several different methods available for the production of drops in such applications are included. Mainly, techniques that are used to produce micron sized (in diameter) drops are highlighted and their use in many of the emerging applications such as printing of three-dimensional arrays of biological cells and printing of flexible electronics are discussed.
Schematics showing the production of drops through (a) electrohydrodynamic (EHD) tip streaming and (b) flow-focusing.
School of Chemical Engineering
Purdue University, West Lafayette, IN 47907
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