Jul 3, 2008
Nanoglassblowing: non-planar devices for easy nanofluidics
Fabricating nanofluidic devices can be a time consuming, difficult and costly process. Once the devices are made, the introduction of fluid and analytes, such as biomolecules, from the macroscopic world into nanochannels presents additional obstacles. One way to overcome these challenges is to use a simple technique called “nanoglassblowing”.
Nanoglassblowing is a new fabrication method for creating smoothly integrated micro and nanofluidic devices with gradual depth changes and very shallow slit-like nanochannels. Using a single layer of contact photolithography and one etch depth in a glass wafer, followed by contact bonding to a second glass wafer and a high temperature anneal, the increased pressure of trapped, heated air pushes out on the softened glass resulting in the outward deflection of the fluidic channel surfaces. In this way, fluidic devices can be created with non-planar, curved and deeper loading channels tapering gradually – like funnels – into planar, rectangular and much shallower slit-like nanochannels. The amount of nanoglassblowing, i.e. the amount of out-of-plane curvature, can be controlled by changing the channel widths or the etch depth of the device. The increased air pressure during nanoglassblowing also prevents very shallow channels from collapsing during the annealing process, enabling the creation of nanochannels so shallow that the depth is limited by the nanoscale surface roughness of the glass wafers.
When fused silica – a type of glass with very low autofluorescence – is used, the resulting devices are ideally suited to single molecule fluorescence microscopy, such as studies of isolated and highly confined DNA molecules. The smooth depth transition between deeper, curved channels and shallower nanochannels solves the problem of integration between micro and nanoscale device regions, allowing easy loading of large analytes, such as long DNA molecules. These non-planar structures may also be useful for optofluidic devices or cellular studies.
Nanoglassblowing promises to expand the availability and utility of glass micro and nanofluidic devices by providing a simple means to fabricate and integrate non-planar device features, continuous channel depth changes from tens of micrometers to a few nanometers, and very shallow slit-like nanochannels.
About the author
Elizabeth Strychalski is a graduate student in the Department of Physics, working in H G Craighead’s research group in the School of Applied and Engineering Physics at Cornell University. Samuel Stavis is a physical scientist and National Research Council research associate in the Semiconductor Electronics Division at the National Institute of Standards and Technology.