Nonstandard Inkjets

Inkjet printers eject drops from microscopic nozzles and deposit them on substrates. For a number of years after its initial development, inkjet printing remained a method for visualizing computer output and printing documents. Beginning in the late 1990s, a number of researchers realized that inkjet printers could be employed as robotic pipettes to create microarrays, manufacture three-dimensional parts and spherical particles, print electrical devices, and facilitate combinatorial chemistry. Although most inks are low-viscosity Newtonian fluids, liquids in new applications are complex fluids. At the same time that these new applications were emerging, the replacement of traditional photography by digital imaging and the quest for ever-faster printing speeds resulted in the development of novel printing methods. Whereas most previous reviews of the field have focused on evaluations of well-known printing methods, this review instead presents a critical analysis from a fluid mechanics perspective of the recent developments in nonstandard printing techniques and the increasingly widespread use of nonstandard inks of complex fluids.