Non-Optical, Label-free Electrical Capacitance Imaging of Microorganisms

Microbiologists are interested in experimental systems that can probe natural habitats, however microbes live in diverse environments and can occupy biological roles spanning many timescales. Exploring the full scope of microbial activity requires imaging systems tailored to each environment, and standard methods such as fluorescence microscopy are not always the appropriate tool. We present a non-optical, Electrical Capacitance Imaging (ECI) system that occupies a new niche in microbial imaging, using an array of complementary metal–oxide–semiconductor (CMOS) transistors to make local measurements of the chemical composition of a sample. Cells, extracellular material, air, and aqueous media all have different dielectric properties, which allows the CMOS to capture high contrast electrochemical images of biological samples. ECI enables experiments in new environments with new species, as it can readily be used for non-model or intractable species, and it is compact, cheap and label-free, with a high frame rate and large field-of-view, spanning millimeter-scale fields of view with micrometer-scale resolution. The physical robustness of our sensor enables weeks-long time lapse imaging experiments, while its low cost and small size facilitates its use for imaging in the field.