Optical multi-physical field imaging within single cells.

Intracellular energy conversion and information transfer are associated with local fluctuations of multiple physical fields, including chemical concentration field, thermal field, magnetic field, electric field and mechanical force field. How these fields coordinately influence cellular activities in space and time remains largely unknown. Imaging platforms that convert physical field fluctuations into optical signals provide essential tools for in situ sensing of these invisible physical fields at the single cell level. While existing reviews largely focus on optical probes for a single physical field, a systematic discussion linking cellular activities to multi-field synergy is still lacking. In this review, we propose the concept of "physical field-optical signal conversion" as a bridge that links physical field fluctuations to optical signals, and then systematically summarize signal readout systems designed for imaging multiple physical fields in single living cells. We summarize in detail how multi-physical field imaging can address biological questions that single dimensional detection cannot resolve. Finally, we comprehensively discuss the challenges and future prospects of single cell multi-physical field imaging, with the aim of fostering a deeper understanding of intracellular signalling pathways and life processes.