Schematic of the developed stochastic model. The dotted squares represent the states in solution and the dotted half-squares represent the states on the surface. Originally, the blocking molecule is adsorbed to the surface because its adsorption energy state is lower than that in the aqueous environment. By changing the surface potential to increase the adsorption energy state of the blocking molecules, there is a certain probability that the blocking molecule will diffuse away from the surface, leaving the adsorption site available to biomolecules. In this case, biomolecules can diffuse and attach themselves to the substrate surface. The dotted-dashed line represents the diffusion process in the solution.
(a) Cross-section schematic of the device used in the developed model. The ITO electrode is used to apply electrical voltage to change the surface potential. The oxide and parylene function as the dielectric material. (b) A simplified equivalent circuit model as electrical voltage is applied. represents the resistance within the ionic buffer solution. Since the buffer solution directly contacts the ground ITO electrode, we assume that the solution is electrically in contact with the ground ITO electrode.
(a) Schematic of the ITO electrode design for our biomolecular patterning experiment driven by electrical potential. It should be noted that most of the ITO electrodes are covered with oxide/parylene dielectric material, except for the ground electrode in the experimental region. (b) A photograph of the fabricated device; the ITO electrode is not visible because of its transparency. The white bar represents 1 cm.
Comparison of theoretical prediction and the experimental result obtained by electroactivation methods . The asymmetric behavior can be modeled by considering the charge carried by the biomolecules.
Experimental result of submicron BSA patterning. (a) Schematic of the BSA patterning experiment. The linewidth of the ITO electrode was 150 nm as patterned by e-beam lithography. (b) Fluorescent image of the experiment. The white bar represents . [(c) and (d)] Fluorescent intensity analysis of the analyzed line. Because each pixel of the image represents 60 nm, there were three pixels, a size equivalent to 180 nm, which is within the maximum fluorescent intensity. Considering the fabrication tolerance and charge coupled device resolution limitation, this result was similar to that obtained with the fabricated submicron electrode.
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