Nanofluidic Diagnostic Chip: Resistive-Pulse Molecule Sensing

Nanofluidic Diagnostic Chip

Idle — no translocation

Applied voltage 80 mV

Nanochannel diameter 60 nm

Sample flow rate Medium

Electrical noise Low

Analyte mix

Live readout

Baseline current

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Instant current

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Events detected

Clogs (channel too small)

Avg dwell time

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Last event species

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How it works

A steady voltage drives ions through a fluid-filled nanochannel narrow enough that a single biomolecule fills a real fraction of its cross-section — the Coulter / resistive-pulse principle. With nothing in the constriction, the ionic current sits at a baseline set by the channel's conductance (∝ diameter²) times the applied voltage. When a molecule drifts into the constriction it displaces conducting electrolyte, so the current dips for exactly as long as the molecule occupies the narrowest point.

I_baseline  ~ d_channel² · V
ΔI / I_baseline  ~ (d_particle / d_channel)²
dwell time  ~ channel length / (mobility · V)

Voltage — higher voltage increases baseline current and speeds up electrophoretic drift, giving shorter, shallower-looking dips but a faster read-out rate.
Channel diameter — a narrower channel raises the relative blockage (better size discrimination) but risks clogging when a particle is nearly as big as the channel itself.
Dip depth encodes particle volume, dip duration encodes how long it took to translocate — together they let the trace distinguish DNA fragments, proteins and virus-like particles without ever imaging them directly.

DNA fragment (~6 nm) Protein (~16 nm) Virus-like particle (~30 nm)

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