Disclosed herein are systems and devices for detecting molecules. In some embodiments, a system for detecting molecules comprises an amplifier and a nanopore unit, wherein the nanopore unit comprises a nanopore, a sense electrode, a counter electrode, and a shield situated between the sense electrode and the counter electrode and coupled to an output of the amplifier. The shield may be recessed from a hole in the nanopore. A system or device may include an array of nanopore units that may share some components, such as a read amplifier, a digitizer, drive circuitry, control logic, and/or a multiplexer.