Mass-produced microvalves are the key to scalable production of disposable, plug-and-play microfluidic devices
The elusive ‘lab on a chip’ capable of shrinking and integrating operations normally performed in a chemical or medical laboratory on to a single chip smaller than a credit card, may soon be realized thanks to disposable, plug-and-play microfluidic devices developed by A*STAR researchers1.
Microfluidic systems use networks of channels much narrower than a human hair to control the movement of miniscule amounts of fluids. Recent advances in microfluidics technology have proven invaluable for immediate point-of-care diagnosis of diseases and have greatly improved enzymatic and DNA analysis. High throughput microfluidic systems are also being employed in stem cell studies and for the discovery of new drugs.
A stumbling block for successful miniaturization and commercialization of fully integrated microfluidic systems, however, has been the development of reliable microfluidic components, such as microvalves and micropumps. Zhenfeng Wang and colleagues from the Singapore Institute of Manufacturing Technology (SIMTech), A*STAR have removed that obstacle by developing an efficient and scalable method to fabricate disposable plug-and-play microfluidic devices.
“Integrating valves and pumps into thermoplastic devices is usually challenging and costly because the fabrication process is very complicated,” says Wang. “Mass-producing the microvalve module separately from the main device, however, makes the fabrication of the main device relatively simple and robust.”
Scientists at the U.S. Department of Energy’s Argonne National Laboratory have discovered a way to use a microscopic swirling flow to rapidly clear a circle of tiny bacteria or swimming robots.
“This discovery offers a new approach for control and manipulation of microscopic swimmers,” said Argonne physicist and co-author Igor Aronson, and it could be useful in tiny microfluidic (“lab-on-a-chip”) devices that can quickly run chemical or biological analyses or perform tasks.
In the study, published in Nature Communications, the researchers placed a magnetic particle in the center of a liquid film filled with swimming bacteria.
Normally the bacteria swim randomly; but when scientists spun the particle by applying a rotating magnetic field, the swimmers shot away from the center, like a school of fish that suddenly realized there’s a shark in their midst.
What’s actually happening is that the particle is rotating, creating a small vortex around itself. The bacteria swim parallel to the stream lines and are quickly pushed outward — except for a few that get sucked in right next to the particle.
They’re not pushed out by centrifugal force, said Argonne scientist Andrey Sokolov, who co-authored the paper; dead bacteria, which aren’t swimming, are not pushed out with their living companions.
“Because of the curvature of the flow, some swim in and are trapped on the rotating particle, and others are forced to swim out of the curved flow,” Sokolov said.
This technique could separate live from dead bacteria, or different species, bacterial strains or mutants from one another. “The shape and swimming rates of different species would mean they separate,” Aronson said.
“At certain frequencies of rotation, the bacteria self-organize into a spiral-shaped halo, creating a microscopic galaxy — similar to our galaxy Milky Way, but trillions of trillions (1024) of times smaller,” Sokolov said.
In addition to new understanding of the forces governing microswimmers and their environments, the vortex technique could help prevent biofilms from forming and disrupting microfluidic devices, the authors suggested.
They are particularly interested in creating systems in which microswimmers could assemble gears to build a tiny machine and then power it, Aronson said.
Aronson and Sokolov also modeled the results theoretically and saw good alignment between computer models and observed results, they said.
Learn more: Moving microswimmers with tiny swirling flows