Nonlinear Electrical and Optical Properties of Nano Sensor Array for Stochastic Molecular Interactions
Date Issued
2009
Date
2009
Author(s)
Lu, Hui-Hsin
Abstract
In the biochip applications, the mechanism of specific molecular recognition plays a fundamental role for molecular diagnosis. Traditionally, the dynamics of such an interaction are obtained by spatial and temporal summations of measured signals at macroscopic scale. However, it should be feasible to acquire such information in microscopic environment at single molecule level. The goal of this research is to develop platform technologies for a novel "digital nanoarray", with feature size down to 50 nm, to explore the microscopic measurement of stochastic behaviour at single molecule level and the feasibility studies of acquiring molecular dynamics by spatial-temporal summations of non-labelling biomolecules. These platform technologies include (1) nanofabrication of zero dimensional (0 D) nanodot array for developing a biomimicking platform and one-dimensional (1 D) nanowire array of conducting polymer for NO gas sensing; (2) a multi-functional dark-field microscopy (DFM) with nano-resolution down to 40 nm and spectroscopic function for characterizing observed nanostructure; and (3) a theoretical model for simulation and analysis of one and two dimensional of stochastic molecular interaction. First of all, we have used dip-pen nanotechnology (DPN) to fabricate nanoarray and nanowires for the studies of their nonlinear optical and electrical properties at large scale. With the fabricated nanodot array of 50 nm in diameter, we were able to immobilize bio-molecules on to prepared surface and acquire both 1 D and 2 D signals for further calculation of the spatial-temporal summations. The non-labeling detection of biomolecular recognition has been done by scanning images of AFM, and the resultant height of streptavidin is about 4 nm, which is close to the theoretical value. To improve the quality of surface preparation, we have used the atomic layer deposition (ALD) to deposit a 2 nm thickness of alumina oxide as a passivation layer to minimize non-specific binding to the native glass surface. We have compared the performance of both oxide surface of germanium and silicon substrate with the bare silicon surface. In the prepared 1 Dnanowire of both 68 nm and 300nm in line width, we are able to precisely align the nanowires across the gap of two microelectrodes. The nonlinear I-V curves of single nanowire were measured and analyzed at room temperature for practical applications. Several parallel and series circuitries of nanowire are measured for the verification of theoretical calculation. Finally, the nanowire array is applied for NO detection. In order to observe the stochastic behavior of single molecule on the digital nanoarray, it is essential to develop an optical microscopy beyond the diffraction limits. Herein, we reported a multifunctional optical microscopic system that combined the features of dark-field microscopy (DFM) with a spectrophotometric function to characterize the nanoarray for both qualitative and quantitative analysis. We have used various formats of optical storage discs, which have different feature sizes in the pitch of track patterns, to demonstrate the resolving power of this system. The calculated resolution is down to 40 nm. Moreover, a thin gold layer is deposited on the disc to study the optical enhancement of pit features and the change of absorption peaks due to surface Plasmon resonance (SPR) effect. A significant change of absorption peak is obtained by depositing a thin film of biolmolecules on the gold film. These results indicate the possible use of this nanoarray platform on medical diagnosis. The stochastic model of behavior of biomolecular interactions is similar to the bi-state (on-off) of channel proteins. Our simulation results show that 100 of molecular interactions are the same in both 1 D and 2 D signals. After this simulation process, we are able to determine the proper size of nanoarray by evaluating the reasonable errors of possibility. We have used deposited 1 D data from internet for our own purposes. This model can be applied to the multi-state systems in the future.
Subjects
biomimicking platform
dip-pen nanolithography
digital nanoarray
dark-field microscopy
PEDOT nanowire.
Type
thesis
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