New “e-jet” process targets lower-cost printed electronics

September 7, 2007 – Researchers at the U. of Illinois say they have devices an electrohydrodynamic jet (“e-jet”) printing process that can produce patterns and functional devices with better resolution “significantly exceeding” other inkjet technologies, with potential application in large-area circuits, displays, and phototovoltaic modules.

The paper, posted online in Nature Materials, describes e-jet printing using electric fields to pull fluid out of a nozzle, unlike conventional inkjet printers which use heat or mechanical vibrations to propel the droplets. In their work, a gold-coated nanoscale nozzle (~300nm dia.) is mounted on a computer-controlled mechanical support, and an organic coating on the gold ensures clean flow of the ink through the nozzle toward the target, with droplets ejected onto a moving substrate to produce patterns. They say the method can produce linewidths down to 700nm and 250nm dots. Thin-film transistors with aligned arrays of single-walled carbon nanotubes, and e-jet-printed source/drain electrodes, were printed on flexible plastic substrates, “with properties comparable to similar devices fabricated with conventional photolithographic methods,” they claim, in a statement.

“As an industrial process, this work opens up the possibility for low-cost and high-performance printed electronics and other systems that involve materials that cannot be manipulated with more common patterning methods derived from microelectronics fabrication,” stated Placid Ferreira, Pro. of Mechanical Science and Engineering. Fellow U. Illinois prof. John Rogers added that the high-resolution form of e-jet printing can also be used for diverse systems “such as printing microarrays of DNA spots for bioanalysis, or printing carbon nanotubes and other classes of nanomaterials.”

The e-jet method can also work with various organic and inorganic inks, including suspensions of solid objects such as nanoscale silicon rods, and with results also “extending to the submicron range,” the researchers noted.


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