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Research solves fundamental inkjet problem

Doctoral candidate Riberet Almieda (left) and Jae Wan Kwon, an associate professor of electrical engineering, developed a device to keep inkjet printer heads from clogging.

After more than 100 years of research, inkjet-printing technology reached consumer markets in the form of desktop printers in the late 1980s. In recent years, innovative applications for the technology — also known as microfluidic systems — have burgeoned including 3D prototype printing processes for business and industry, bio-applications such as printable human tissues, solar cell production and even a drug dispensing system, to name a few.

Yet in spite of increasing numbers of innovative applications that make use of inkjet technology, clogged print heads have plagued its use from its inception.

“Clogging comes from the drying process; you can’t avoid evaporation,” said Jae Wan Kwon, a University of Missouri electrical engineering professor, who looked to nature to resolve the costly dilemma.

Kwon was inspired by the function of the human eye for the solution he devised to solve the problem. He said that even though many current printers are designed with doors to block the flow of air, the problem of clogged ink head nozzles persists.

“The mechanism of the human eye includes a thin oily layer to keep it from drying out,” he said, explaining the process that occurs as a function of blinking, during which a lipid layer is spread-covered as a shield to slow evaporation of the eye’s moisture.

Once he conceptualized the solution, Kwon said, he was excited to implement it. He was awarded a $268,000 research grant from the National Science Foundation to pursue his idea.

As a result, Kwon and doctoral student Riberet Almeida have devised a system that uses an electric field to move a droplet of silicon oil over the printer’s nozzle when it is not in use.

“Solid state materials can change their shapes with an application of an electric field, even though you may not be able to see it with the naked eye,” said Almeida. “We apply an electric field and piezoelectricity causes the fluid in the chamber to eject the fluid droplets.”

Kwon said the electrostatic force easily can be controlled digitally.

In order to demonstrate the breakthrough, Almeida said he needed to capture good and clear photos of its actual occurrence.

“My biggest challenge was to image the ejected tiny droplets moving at high speed, and I have spent a long time perfecting my techniques to capture the droplets on video, analyzing it frame by frame,” he said.

Almeida presented his work at the 2012 Solid-State Sensors, Actuators and Microsystems Workshop.

“It is the very top conference in the world for this type of work,” he said, noting that to be accepted as a presenter is very prestigious.

A paper detailing the research appeared in the Journal of Microelectromechanical Systems. A number of companies have expressed interest in the project.

View how the device works here (courtesy of MU News Bureau).