Nanotech News

June 20, 2005

Making 3-D Microfluidic Mixers

Mixing is a critical process in any analytical technique, but mixing in a microfluidic environment is challenging because of the absence of turbulence in microfluidic channels. Most mixing schemes that have been developed rely on active devices such as rotating magnetic bars or pneumatically operated membranes, but these mixers introduce complexity into a microfluidics device. A new possibility, discussed in a paper published in the journal Nano Letters, is to mix fluids by forcing them through a complex three-dimensional network of nanoscale paths fabricated within the channels of a microfluidic device.

In reporting their work, a team led by John Rogers, Ph.D., at the University of Illinois at Urbana/Champaign, describes a new lithographic technique that enables them to craft over 2000 nanofluidic pathways to completely fill the cross section of a microfluidic channel. This method, which the Rogers group calls proximity field nanopatterning, uses an embossed mask to focus light in a complex pattern of intensities on a photosensitive material layered on top of glass. Using confocal microscopy, the researchers were then able to visualize fluid flow through the resulting maze of nanochannels. These confocal images showed clearly that fluid flowed through normal cells with no detectable turbulence of mixing. In contrast, fluid flowing through the network of nanoscale paths were well-mixed at a variety of flow rates. The researchers did note that the nanoscale paths might be susceptible to clogging and that they could create significant pressure drops across the microfluidic channel.

This work appeared in a paper titled, "Optically fabricated three dimensional nanofluidic mixers for microfluidic devices." This paper was posted online in advance of publication. An abstract is available on the journal's website.
View abstract.