A water compartment cell culture lid enables stable longitudinal recording of neuronal networks in vitro

Longitudinal electrophysiological recordings of neuronal networks are essential for studying network maturation, plasticity, and pharmacological responses. Yet current microelectrode array (MEA) approaches are limited by evaporation-induced drift in culture conditions, exacerbated by heat dissipation from active recording electronics on CMOS-based high-density MEAs. We present a cell culture lid featuring a water compartment at its interface that eliminates evaporation whilst maintaining gas exchange. Combined with a custom incubator that uses independent temperature control of the MEA to prevent condensation, the system enables stable, un-interrupted recordings for weeks. We show that perturbations in firing rate and functional connectivity following medium exchange are significantly reduced by suppressing evaporation. We demonstrate continuous 35-day recordings of patterned human iPSC-derived neuronal networks with a single medium exchange, revealing the spontaneous emergence and consolidation of spatiotemporal firing patterns during maturation. All design files are provided to facilitate adoption across culturing platforms, enabling un-interrupted longitudinal interfacing with network dynamics for studies of plasticity, chronic pharmacology, and developmental trajectories in individual cultures.