Optical Microsphere Nano-Imaging: Progress and Challenges

Abstract

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 nano-imaging 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 λ6-λ8 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.