Fig. 4

Paralleled detection of PSA using 3 × 3 nanopore array. Concatenated ionic current traces showing multiple sequential blocking and unblocking events of (a) 3 × 3 array of 27 nm nanopores modified with silane-EG₆ SAM by 50 nm MNPs when there was no PSA present. b 3 × 3 array of 27 nm nanopores modified with silane-EG₆ SAM by anti-PSA functionalised 50 nm MNPs in the presence of 5 pg mL⁻¹ PSA. c 3 × 3 array of 27 nm nanopores modified with silane-EG₆ SAM by anti-PSA functionalised 50 nm MNPs in the presence of 10 pg mL⁻¹ bovine serum albumin (BSA). All ionic current traces were recorded in 100 mM KCl and 10 mM Tris pH 7.4 at a potential bias of 100 mV, low-pass-filtered at 10 kHz and sampled at 250 kHz. (d) Simulation of the 3 × 3 array of 30 nm nanopores separated by 3 μm apart from each other. The simulation region consists of a cylindrical volume of 20 μm in diameter and 20.18 μm in height representing the electrolyte medium. A potential bias of +100 mV was applied from the top boundary whereas the bottom boundary was defined as grounded (0 mV). (i) Top, (ii) isometric, (iii) side view of 3D plots of electric field lines with one nanopore blocked by a 50 nm MNP. Black solid lines represent the interface boundaries whereas blue solid lines denote the simulated electric field lines. (iv) 2D cross-sectional plot of electrical potential and field lines of 3 nanopores (two unblocked and one blocked) as a colour map and white solid lines respectively. SiN membranes of a thickness of 180 nm were employed here for the paralleled detection and simulation work