Assistant Professor Tingyi “Leo” Liu of the Mechanical and Industrial Engineering (MIE) Department is part of a team of researchers from UMass Amherst and UCLA who have developed a more cost-efficient and dependable method of manipulating small droplets on a hydrophilic surface. According to the researchers, the new method is “promising a simple and reliable microfluid platform for a broad range of applications” that could go far beyond current functions related to liquid lenses and diagnostics kits.
This new strategy is described in a paper published in the journal Nature. Liu is head of the Interdisciplinary Interface Engineering Laboratory (Inter²EngrLAB) in the College of Engineering.
According to the UMass News Office article, Liu says the new method reverses what scientists already know about a phenomenon called electrowetting, in which droplets of liquid are attracted to and spread on a conductive surface in response to an applied voltage.
Liu explains that, despite being known for more than a century, electrowetting generally requires additional coatings to make it practical for applications. Such a modified configuration of electrowetting has produced great success in the past 20 years, but it also leaves unsolved reliability challenges.
As Liu and his colleagues told the News Office, “Here we demonstrate droplet manipulation that uses electrical signals to induce the liquid to de-wet rather than wet a hydrophilic conductive surface without the need for added layers.”
Liu says that the millimeter-sized droplets are induced to move across the surface by an electric signal that causes the liquid to detach on one side, thus moving it. Other basic manipulations including creating, cutting, and merging of droplets can also be performed in similar ways.
Liu says this new process removes the complexity of the system and the reliability challenges found in existing electrowetting technique, as well as reducing the cost of manufacturing as well. The system has been shown to handle a wide range of fluids, including common buffers and organic solvents, thereby being used for purposes surpassing current electrowetting applications such as liquid lenses and diagnostics kits, according to the researchers.
The other members of the team from UCLA are Professors Chang-Jin “CJ” Kim and R. Michael van Dam, as well as doctoral students Jia Li and Noel S. Ha.
In addition to his faculty appointment in the College of Engineering, Liu is affiliated with the Institute for Applied Life Sciences (IALS), which combines deep and interdisciplinary expertise from 29 departments on the UMass Amherst campus to translate fundamental research into innovations that benefit humankind. (August 2019)