New method can create fluidic channels with unusual shapes

Most micro- and nanofluidic chips contain channels with flat rectangular sides. A novel technique called “nanoglassblowing” can create curved micro- and nanochannels from glass, including funnels that can serve as conduits for loading individual molecules into very shallow, confining channels. The nanoglassblowing technique was developed by researchers at the National Institute of Standards and Technology in Gaithersburg, Md., and at Cornell University in Ithaca, N.Y.

These fluorescence microscopy images show long DNA molecules of 48,500 base pairs in a deep curved region of a nanoglassblown device (left), and the same DNA stretched out and confined after being loaded into a 7-nm-deep channel using a funnel-shaped channel (right). Scale bar =10 μm. Reprinted with permission of Nanotechnology.

The investigators note that the technique also could be used to design and create optical features such as lenses and waveguides with nonplanar shapes. As a consequence of their unusual shapes, these features could have optical properties never before observed in a micro- or nanofluidic device.

In their demonstration of nanoglassblowing, the researchers chemically etched trenches into glass and then bonded the cover on top of it. They exposed the glass to high temperatures, and the trapped air expanded it into various shapes that depended on several factors, not the least of which was the geometry of the initial trenches. This physical principle is similar to what glassblowers have been doing for thousands of years to shape ornaments, jars and other items. The process is detailed in a Nanotechnology paper that was published online on June 17, 2008.

The scientists created funnels several micrometers wide and about 1 μm deep that tapered to depths as shallow as 7 nm. The funnels facilitated loading DNA into these shallow nanochannels, which not only restrained but also unraveled and straightened the DNA, thus making the molecules more accessible for investigation. The smaller volume in the nanochannels also conveniently leads to lower background during fluorescence imaging. The researchers said that these channels could facilitate sorting or sequencing DNA in fluidic devices and that nanoglassblowing also could create chambers or networks of channels to hold cells for culturing.