Investigation of Shielding Strategies to Mitigate Noise in Nanopore Recordings

Shielding against electromagnetic interference (EMI), vibration, and mechanical noise is crucial for reliable performance of sensitive electronics, especially in high-disturbance environments. While Faraday cages are ubiquitously used for this purpose, they are often implemented simply as metal boxes enclosing the measurement system, without accounting for critical design factors such as skin depth. In this study, we have investigated a host of factors to understand noise origins, noise coupling pathways, and systematic treatment for effective shielding against them beyond the common metal box treatment. To accomplish this, we pursued the construction of a nested Faraday system conducive for low-noise data acquisition, investigating powerline quality, grounding strategies for the Faraday cage, connectivity solutions for maintaining Faraday cage integrity, and relative positioning of the components in the measurement setup. Our findings have rendered noise in current measurements to be in the vicinity of biological nanopores. For example, with 100 mM KCl, the RMS current (Irms) at 10 kHz was found to be 4.1±0.1 pA, while that of α-hemolysin is reported to be ~2-3 pA. This low noise floor has allowed us to detect translocation of DNA under challenging low electrolyte conditions (i.e., 10 mM KCl) using the highest lowpass filter setting of the Axopatch 200B (i.e., 100 kHz). Moreover, with necessary modifications, these findings were extended to the MHz-level bandwidth regime, where events up to 10 MHz of sampling rate were observed with unfiltered traces. Although our findings broadly cater to solid-state nanopore (SSN) sensing, their applicability should extend beyond SSNs into other sensitive electronic systems.