in polydimethylsiloxane using sacrificial electrospun
polyethylene oxide nanofibers
Leon Bellan and Elizabeth Strychalski
School of Applied and Engineering Physics, Cornell University
We have used electrospun polyethylene oxide (PEO) nanofibers as sacrificial templates to form
nanofluidic channels in polydimethylsiloxane (PDMS). By depositing fibers on silicon templates
incorporating larger structures, we demonstrate that these nanochannels can be
integrated easily with microfluidics. We
use fluorescence microscopy to image channels filled with dye solution. The utility of the hybrid micro- and
nanofluidic PDMS structures for single molecule observation and manipulation
was demonstrated by introducing single molecules of λ DNA into the channels. This nanofabrication technique allows the
simple construction of integrated micro- and nanofluidic PDMS structures
without lithographic nanofabrication techniques.
Using sacrificial electrospun polyethylene oxide (PEO) fibers, we have formed nanofluidic channels in
Electrospinning is the process of forming nanofibers from a polymer
solution using an electrically forced fluid jet.1 These fibers can be used as lithographic
or sacrificial structures5 to form nanoscale features in
other materials. In this work,
electrospun fibers were deposited onto a silicon chip, and PDMS was poured on
top and allowed to cure. The PEO fibers were removed from the cured PDMS by
soaking the material in water, leaving nanochannels (process outline in Figure
1). We demonstrated that these
nanochannels can be easily integrated with standard microfluidics by depositing
fibers on patterned silicon chips.
Imaging the channel cross-sections using a scanning electron microscope
revealed the channels to have sub-micron diameters (Figure 2). To ensure that the channels were open, we
filled them with fluorescent dye and imaged the filled channels. Figure 3 shows images of filled devices
consisting of random and aligned channels.
We also introduced single molecules of λ DNA
into the channels, demonstrating the utility of these integrated micro- and nanofluidic structures for single molecule
observation and manipulation. The paths
of several isolated molecules of DNA
are shown in Figure 4.
Using this nanofabrication technique, it is possible to
fabricate hybrid micro- and nanofluidic PDMS structures without using expensive
and time-consuming conventional nanofabrication techniques. These fluidic structures could be used for
several purposes, ranging from separating and analyzing biomolecules6 to forming materials with
artificial vascular structure.7 Of the materials used to form microfluidic
structures, PDMS remains one of the most popular due to its versatility and
ease of use. Similarly, PEO is one of the most popular materials to
electrospin because it is easy to work with, water soluble, and non-toxic. A
fabrication process that combines these two materials is advantageous because
the materials systems involved are well characterized and commonly used.
Moreover, it should be straightforward to scale up this fabrication process to
allow high throughput formation of micro- and nanoscale devices, rendering
several applications previously confined to the research lab potentially
Figure 1- Process outline
Figure 2 - SEM
image of nanochannel cross section
Figure 3- Fluorescence microscopy
image of channels filled with dye
Figure 4 - Fluorescence microscopy image of paths
traveled by fluorescently labeled DNA
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