Single-molecule sensing by inserting a disposable strip into a USB-enabled mobile device. (a) The 3D printed strip houses the fluidics and nanopore chip (Supplementary Fig. S1). Replaceable Ag/AgCl electrodes connect the fluidic channels with the circuitry in the reader device. Reagents and buffer are loaded into one channel, with buffer only in the other channel. (b) The strip is inserted into the handheld device that houses voltage-clamp circuitry, which supplies a voltage across the pore and measures ionic current through the pore. Data transfer is through a USB port for event detection and analysis on a PC or laptop (Supplementary Figs S3 and S4). (c) Schematic of diffusing DNA above the nanopore on the reagent-added side, during (i) an open nanopore period, and (ii) passage of a single DNA through the pore into the voltage-positive side. (d) A representative electrical current event caused by a single dsDNA passing through a nanopore, annotating (i) the open pore periods and (ii) the passage duration. Events are quantified by the passage duration and the maximum conductance depth (max δG = δI/V, V = 0.1 V). (e) An all-event scatter plot of max δG versus duration displays 1049 events of 5.6 kb dsDNA recorded in 5 minutes with a 22 nm diameter nanopore.