The schematic of confined evaporation process for fabrication of PDMS nanochannel array. The protein (i.e., BSA) solution evaporates and the BSA molecules deposit inside microchannels to form line structures at nano/micro scale. PDMS nanochannels can be fabricated by replicating the line structures, followed by bonding the micro/nanogrooves onto glass substrate.
The images of BSA deposit for solution concentration (a) 0.5 wt. % and (b) 1 wt. %. (a1) and (b1) are the optical images. (a2) and (b2) are SEM images. (a3) and (b3) are AFM images with corresponding measurements (a4) and (b4). (The scale bar in the inset of SEM images is 100 nm.)
The SEM images of BSA deposit at the bottom corners of and along the microchannel.
The height of the deposited BSA structures at different solution concentrations. The average heights of the deposited BSA structures from using 0.5 wt. %, 1 wt. %, 2 wt. %, and 3 wt. % solution are approximately 210, 530, 1030, and 1840 nm, respectively.
The images of (a) the deposited BSA structures and (b) the negative relief near the open end of the microchannels (1 wt. % solution was used)
(a) Top view and (b) 45° tilted view of the negative relief of the deposited BSA structures. (The scale bar in the inset is 1 μm)
The nanochannels are filled with the 0.1 wt. % BSA solution from the inlet to the outlet. The solution was added with fluorescein dye for visualization. (“L” stands for the distance from the inlet)
Stretching of DNA molecules (a) near the inlet (micro to nano region) and (b) at about 2 mm away from the inlet of the nanochannel. The maximum elongation of λ-DNA reaches 10 μm, which is about 50% of its fully extended length. (Scale bar: 20 μm)
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