Microsphere Super-resolution Optical Imaging: Principles, Techniques, and Applications

Optical microscopy plays a key role in the fields such as biology, medicine, materials science, and precision measurement, providing a powerful tool for exploration in microscales. However, traditional optical microscopy systems are constrained by the diffraction limit, with a maximum resolution of approximately half of wavelength (λ/2). In recent years, super-resolution imaging beyond the diffraction limit has attracted attention in the field of microscopy. Dielectric microsphere lenses have demonstrated the capability to focus the incident light in a narrow region breaking Abbe's diffraction limit with the full width at half maximum of focal spot smaller than λ/2. Microsphere super-resolution imaging demonstrates the advantages prior to other alternative techniques, including the easy-to-use, free of fluorescence labels, real-time imaging, and compatibility with established microscopy systems. It opens up new opportunities in academic research and practical applications. In this review, the principle of microsphere super-resolution imaging was introduced. Subsequently, the key parameters that affect imaging capability were analyzed in details, including microsphere optical properties, environmental suitability, and controllability. Finally, the applications of microsphere super-resolution imaging in biomedicine, semiconductors, and nanomaterials were explored. Furthermore, the major challenges to development of microsphere super-resolution imagining were prospected.