Optical Microsphere Nano-Imaging: Progress and Challenges

The optical diffraction effect imposes a radical obstacle preventing conventional optical microscopes from achieving an imaging resolution beyond the Abbe diffraction limit and thereby restricting their usage in a multitude of nanoscale applications. Over the past decade, the optical microsphere nanoimaging technique has been demonstrated to be a cost-effective solution for overcoming the diffraction limit and has achieved an imaging resolution of up to about k6 - 8k in a real-time and label-free manner, making it highly competitive among numerous super-resolution imaging technologies. In this review, we summarize the underlying nano-imaging mechanisms of the microsphere nanoscope and key advancements aimed at imaging performance enhancement: first, to change the working environment or modify the peripheral hardware of a single microsphere nanoscope at the system level; second, to compose the microsphere compound lens; and third, to engineer the geometry or ingredients of microspheres. We also analyze challenges yet to be overcome in optical microsphere nano-imaging, followed by an outlook of this technique. (c) 2024 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).