Fig. 1

Nanopore blockade sensor. a (i) Schematics and scanning electron micrographs of (top) a solid-state nanopore, inset: a 48 nm nanopore, scale bar: 100 nm; (bottom) a nanopore array in SiN membrane, inset: a 3 × 3 array of nanopores with 0.5 μm spacing between each pores, scale bar: 200 nm. (ii) Illustration of a chemically modified SiN nanopore with silane-EG₆-(anti-PSA) self-assembled monolayer (SAM); EG equates to ethylene glycol. (iii) Illustration of an (anti-PSA)-conjugated MNP used in this work. Inset: chemical structure of the (anti-PSA)-EG₆ immobilised onto the amine-rich PEI coating of the MNP. b Flow chart illustrates the sample preparation steps for detection of PSA in a sample. (i) Sample containing PSA was mixed with (anti-PSA)-MNPs. After exposing the MNPs to the sample, the MNPs were then magnetically separated and washed 3 times with PBS. (ii) The MNPs were subsequently added into the cis-chamber of a nanopore flow cell filled with KCl as electrolyte. A potential difference was applied between both sides of the nanopore. c Active filtering of non-specific nanopore blockade events can be achieved by applying a magnetic field from the cis-side. (i) (Anti-PSA)-MNP that non-specifically adsorbed onto the pore surface will be ejected and thus unblocks the pore, whereas, (ii) (anti-PSA)-MNP that contains captured PSA will continue blocking the pore. Blue dashed lines represent the magnetic field lines, B