Polymer Nanochannels Fabricated by Thermomechanical Deformation for Single-Molecule Analysis

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Abstract
A simple method for fabricating nanoscale channels based on thermomechanical deformation of rigid polymer substrates is demonstrated. Polycarbonate preforms containing microchannels with cross-sectional dimensions on the order of tens of micrometers are controllably deformed to produce submicrometer dimensions. The reduced channel dimensions are achieved by heating the preform while applying a uniaxial tensile force to reduce channel cross sections through the Poisson effect. Nanochannels with circular or elliptical cross sections are defined by varying the channel position and preform geometry prior to deformation. Arrays of parallel nanochannels with critical dimensions down to 400 nm are described. Using the fabrication method, a nanochannel network is fabricated for the detection of single protein molecules via confocal fluorescence microscopy. The chip includes a detection channel with cross-sectional dimensions approaching the confocal volume dimensions of the detection optics and a larger adjacent reference channel used to optimize focusing. Detection of fluorescently labeled bovine serum albumin at 15 and 150 nM concentrations is presented, demonstrating the ability to perform single-molecule fluorescence measurements in polycarbonate chips using visible wavelengths for excitation and detection.