Fig. 1.

Nanoconstriction based detection of single nanoparticles and viruses. (a) The schematic demonstrating the device layout: external voltage bias electrodes (H and L) and sensing electrode (S); embedded filters (F); fluid resistor (FR); nanoconstriction (NC); pressure regulated fluidic ports (P1–P6). Nanoparticles in saline suspension flow in the direction of the arrows, and changes in the electrical potential of the fluid adjacent to the nanoconstriction are detected by the sensing electrode S. (b) Analysis of a nanoparticle solution mixture containing 51 nm, 75 nm and 117 nm polystyrene nanoparticles. Left panel shows the output voltage read as a function of time as the nanoparticles pass through the nanoconstriction. Right panel shows the histogram of effective diameter of the nanoparticles detected. (c) Analysis of T7 bacteriophage viruses with an admixture of 117 nm calibration nanoparticles. Left and right panels show the time-trace plot of output voltage and the histogram of effective diameter of detected particles. The dashed lines correspond to DLS measurement of the mixtures. Adapted from ref. 38. ©2011 Macmillan Publishers Ltd: Nature Nanotechnology.