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SPECIAL SECTION ON THE FLUID MECHANICS AND RHEOLOGY OF NONLINEAR MATERIALS AT THE MACRO, MICRO AND NANO SCALE

# Controlled Nanoassembly and Construction of Nanofluidic Devices

[+] Author and Article Information
M. Riegelman, H. Liu

Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104

H. H. Bau1

Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104bau@seas.upenn.edu

1

All correspondence should be directed to this author.

J. Fluids Eng 128(1), 6-13 (Apr 11, 2005) (8 pages) doi:10.1115/1.2136932 History: Received July 09, 2004; Revised April 11, 2005

## Abstract

This paper describes the combined use of controlled nanoassembly and microfabrication (photolithography) to construct multi-walled, carbon, nanotube-based fluidic devices. The nanoassembly technique utilizes dielectrophoresis to position individual nanotubes across the gap between two electrodes patterned on a wafer. The dielectrophoretic migration process was studied theoretically and experimentally. Once a tube had been trapped between a pair of electrodes, photoresist was spun over the wafer and developed to form microfluidic interfaces. Liquid condensation in and evaporation from the nanotubes were observed with optical microscopy. The nanotube-based fluidic devices can be used for studies of fluid transport under extreme confinement and as sensitive sensors.

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## Figures

Figure 2

A schematic depiction of another layout of trapping electrodes. The dimensions of the electrodes are shown in the figure.

Figure 3

A SEM image of a trapped nanotube. The gap between the electrodes is 8μm.

Figure 4

A schematic depiction of a cross section of the nano-fluidic device

Figure 5

A SEM image of the nanofluidic device (top view). The insert (top left) is a magnified view of the region next to the barrier between the two wells, showing the end of the nanotube under the barrier.

Figure 6

Various stages of evaporation of ethylene glycol from the interior of a nanotube. The tube on the left is nearly full; the nanotube on the right is nearly empty.

Figure 7

Images of the nanotube during various stages of the trapping process: 0s(a), 0.2s(b), and 0.28s(c). The nanotube is encircled with an ellipse for better visibility.

Figure 10

A nanotube forest

Figure 11

A schematic description of the model used to calculate the dielectrophoretic and viscous forces acting on the particle and to predict the particle’s trajectory

Figure 12

The electric potential (contour lines) in the gap’s vicinity

Figure 13

Contours of electric field intensity ∣E0∣

Figure 1

Top view of a nanotube-based fluidic device. The trapping electrodes are enclosed with a dashed circle. The gap between the trapping electrodes is 8μm. The image was taken with an optical microscope. The photographs also show electrodes for the induction of electrophoretic flow and for the measurement of ionic currents.

Figure 8

The nanotube’s velocity and inclination angle as functions of the horizontal distance from the tube’s center to the gap’s center. The inclination angle is defined in Fig. 7.

Figure 9

Early stages of the nanotube chain formation process

Figure 14

The electric field intensity ∣E0∣ as a function of x at y=0.2 (solid line), 2 (dashed line), 4 (dashed-dot line), and 10μm (dotted line)

Figure 15

The horizontal velocity Ux as a function of x at (a)y=1 (solid line) and 2μm (dashed line) and (b)y=4 (solid line), 6 (dashed line), and 10μm (dotted line) is depicted as a function of x. The insert depicts a magnified view of the velocity far from the gap.

Figure 16

The vertical velocity Uy at y=4 (solid line), 6 (dashed line), and 10μm (dotted line) is depicted as a function of x. The insert depicts a magnified view of the velocity far from the gap.

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