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Accumulation of bioavailable heavy metals in aquatic environment poses a serious threat to marine communities and human health due to possible trophic transfers through the food chain of toxic, non-degradable, exogenous pollutants. Copper (Cu) is one of the most spread heavy metals in water, and can severely affect primary producers at high doses. Here we show a novel imaging test to assay the dose-dependent effects of Cu on live microalgae identifying stress conditions when they are still capable of sustaining a positive growth. The method relies on Fourier Ptychographic Microscopy (FPM), capable to image large field of view in label-free phase-contrast mode attaining submicron lateral resolution. We uniquely combine FPM with a new multi-scale analysis method based on fractal geometry. The system is able to provide ensemble measurements of thousands of diatoms in the liquid sample simultaneously, while ensuring at same time single-cell imaging and analysis for each diatom. Through new image descriptors, we demonstrate that fractal analysis is suitable for handling the complexity and informative power of such multiscale FPM modality. We successfully tested this new approach by measuring how different concentrations of Cu impact on Skeletonema pseudocostatum diatom populations isolated from the Sarno River mouth. [ABSTRACT FROM AUTHOR]

The electrohydrodynamic effect has been exploited for the fabrication of polymeric microlenses through different approaches. Here we show that microlens arrays obtained with the pyro-EHD self-assembling process exhibit high fill-factor and good level of homogeneity, thus allowing to integrate them in a lightfield microscope. Digital holographic microscopy is used to characterize the fabricated microlens array. Afterwards, a Fourier lightfield microscope is built by placing this microlens array at the Fourier plane of the objective. We demonstrate for the first time that the self-assembled PDMS microlens array is suitable for 3D imaging of microscopic samples, computationally reconstructing the volume of a thick fluorescent sample. • Polymer microlens array fabricated through pyro-EHD self-assembling technique. • Digital holography is used to characterize quantitatively the microlens array. • Polymer microlens array integrated in a Fourier lightfield microscope. • Fluorescent 3D sample is imaged through the Fourier lightfield microscope built. • The volume of the 3D sample is reconstructed computationally. [ABSTRACT FROM AUTHOR]