Date of Graduation

5-2013

Document Type

Thesis

Degree Name

Master of Science in Microelectronics-Photonics (MS)

Degree Level

Graduate

Department

Graduate School

Advisor

Steve Tung

Committee Member

Ken Vickers

Second Committee Member

Jin-Woo Kim

Third Committee Member

Uche Wejinya

Abstract

A transparent nanofluidic system with embedded sensing electrodes was designed and fabricated by integrating Atomic Force Microscopy (AFM) nanolithography, Focused Ion Beam (FIB) milling and metal deposition, and standard microfabrication processing. The fabrication process started with the evaporation of chrome/gold (Cr/Au) onto a Pyrex 7740 wafer followed by photolithography and wet etching of the microchannels. The wafer was patterned a second time to form Au microelectrodes with 15-45 micrometer separation gaps in the nanochannel region. Sensing electrodes (up to one micron wide) were then deposited using FIB to bridge the gaps. The nanochannels were realized through both AFM nanolithography and FIB milling techniques, which simultaneously cut through the electrodes and connected the microchannels. A 100-nanometer (nm) thick layer of amorphous silicon was deposited on a separate Pyrex 7740 substrate by PECVD and used to cap the nanochannel chip through anodic bonding. The completed nanofluidic system was tested successfully for flow patency by pumping Fluorescein Isothiocyanate (FITC) through the nanochannel. The average flow rate in the nanochannel was estimated by monitoring the displacement of the liquid/air interface in the microchannel. The sensing electrodes were used to perform I-V curve measurements of fluids with different electrical conductivities in the nanochannel. As a proof of concept for biomolecule characterization, negatively-charged nanobeads (20-nm yellow-green FluoSpheres®) were translocated through the nanochannel and their corresponding electrical signatures were measured by the embedded sensing electrodes. The result was in general agreement with the electrical tunneling behavior of the nanobeads.

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