Resolution enhancement in evanescent light illumination microscopy using microsphere lenses.

Weakly scattering samples such as low-refractive-index nanomaterials present significant challenges in super-resolution imaging, because their weak scattering signals are difficult to distinguish from background noise. Here, we propose microsphere-enhanced evanescent light illumination microscopy (MS-EIM) for the label-free super-resolution imaging of weakly scattering samples. We used the MS-EIM method to perform simulated imaging of transparent samples with a 100-nm gap to investigate its imaging performance. Subsequently, the feasibility of MS-EIM for super-resolution imaging of weakly scattering samples was experimentally validated. This MS-EIM is a wide-field, real-time imaging technique with potential applications in the field of high-speed, label-free biomedical imaging.