The voltage was applied to the external Ag/AgCl electrode relative to the internal Ag/AgCl electrode. The current was recorded using an AC/DC capable Nanopatch system (Electronic BioSciences, Salt Lake City, Utah). The analog to digital conversion is performed by a Kintex-7 FPGA on a National Instruments PCIe-7857 data acquisition card. The FPGA is programmed to acquire, filter, and down-sample the current data. After appropriate thresholds are set, the FPGA performs threshold detection to detect the passage of a particle through the nanopipette and quickly switch the bias voltage to reverse the direction of the particle motion. The current data is then streamed to the host computer to be displayed and saved. Current-time data were recorded at 50 kHz with a 10 kHz LPF.