Modular Grid Optodes for Simultaneous Multiparameter Imaging via RGB Detection: a Spatially Patterned Approach to High-Resolution Chemical Sensing

High-resolution imaging of chemical gradients is critical for studying complex microscale environments, but conventional planar optodes face limitations in simultaneous multiparameter sensing due to spectral crosstalk and signal overlap. Here, we present a modular alternative using grid optodes, arrays of discrete, selectively responsive sensor spots printed in a checkerboard layout via a custom 3D-printed dispensing system. Each spot responds to either oxygen or pH, enabling parallel detection without optical interference and with a spatial resolution of <400 µm. RGB cameras were used for optical readout, and we evaluated multiple spatial interpolation methods to reconstruct 2D analyte maps from discrete spot data. Nearest-neighbor interpolation followed by mean filtering was found to provide robust image reconstruction. The grid optodes were validated in both controlled agar matrices and sulfidic sediment, achieving imaging performance comparable to conventional planar optodes. This approach offers a modular, scalable, and low-cost platform for high-resolution, multiparameter chemical imaging, compatible with accessible RGB detection systems, and adaptable to diverse sensing formats.