Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Microfluidics: Mixing through oscillations

11.09.2014

A tiny device produces oscillatory flows that enhance the mixing of viscous fluids for chemical reactions.

Devices that manipulate very small volumes of fluids are applied in diverse fields, including printer technology, DNA processing and cooling systems for electronics. For some processes involving fluids, such as mixing, it is useful to generate oscillating flows, but this can be difficult for particularly viscous fluids. Now, A*STAR researchers have developed a microfluidic oscillator that produces oscillations even in very viscous fluids[1].


Top (left) and side (right) views of the device. Fluid flow causes the diaphragm to undergo elastic oscillations, producing an oscillatory flow at the outlet.

Reproduced, with permission, from Ref.1 © 2013 AIP Publishing LLC

“In miniaturized fluidic devices, the viscous force of the fluid dominates the flow, and mixing becomes a challenging task,” says Huanming Xia from the A*STAR Singapore Institute of Manufacturing Technology (SIMTech), who led the study with co-workers at SIMTech and the A*STAR Institute of High Performance Computing. “The microfluidic oscillator is a part of our continuous effort to solve this problem.”

Microfluidic valves and pumps have diaphragms, which are usually made from soft materials, such as rubber, and are operated via external forces. Yet the tiny device, less than 4 millimeters in size, developed by Xia’s team does not need external control. Instead, when the diaphragm is placed in a fluid flow, it responds elastically by wiggling up and down to make the device oscillate automatically (see image). To adapt the design for use with very viscous fluids, the researchers replaced the rubber diaphragm with one made from copper and beryllium foil.

While this device has practical benefits, it also raises theoretical implications about the behavior of microfluidic oscillators. The team found that at low fluid pressures, the flow across the diaphragm does not oscillate. Then, above a particular transition pressure, the flow rate drops and oscillatory flow occurs, increasing in frequency as pressure increases. After performing experimental and theoretical tests for different device shapes, fluid viscosities and diaphragm thicknesses, Xia’s team could expand current theories.

“Flow-induced vibrations are usually related to flow instabilities and analyzed using a spring–mass model,” explains Xia. The transition from laminar flow to oscillatory flow in their new oscillator was counterintuitive, because increased pressure led to reduced flow rates. The team recognized that this behavior was similar to ‘negative differential resistance’ — a well-established concept that describes certain electric circuits in which an increased voltage leads to a lower current.

Xia’s team is currently developing a complete mathematical model of their device using negative resistance and other concepts ‘borrowed’ from electric circuit theory. This should assist them to optimize the device design for practical applications; for example, the enhanced mixing of viscous fluids enabled by the device can intensify and control chemical reactions.

Reference

1. Xia, H. M., Wang, Z. P., Nguyen, V. B., Ng, S. H., Wang, W. et al. Analyzing the transition pressure and viscosity limit of a hydroelastic microfluidic oscillator. Applied Physics Letters 104, 024101 (2014).

Associated links

Lee Swee Heng | Research SEA News
Further information:
http://www.researchsea.com

Further reports about: A*STAR SIMTech Science Xia diaphragm fluids materials microfluidic mixing oscillate oscillations oscillator rubber transition

More articles from Life Sciences:

nachricht Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz

nachricht Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>