Ultraviolet metasurface-assisted photoacoustic microscopy with great enhancement in DOF for fast histology imaging.

Pathology interpretations of tissue rely on the gold standard of histology imaging, potentially hampering timely access to critical information for diagnosis and management of neoplasms because of tedious sample preparations. Slide-free capture of cell nuclei in unprocessed specimens without staining is preferable; however, inevitable irregular surfaces in fresh tissues results in limitations. An ultraviolet metasurface with the ability to generate an ultraviolet optical focus maintaining < 1.1-µm in lateral resolution and ∼290 µm in depth of field (DOF) is proposed for fast, high resolution, label-free photoacoustic histological imaging of unprocessed tissues with uneven surfaces. Microanatomical characteristics of the cell nuclei can be observed, as demonstrated by the mouse brain samples that were cut by hand and a ∼3 × 3-mm field of view was imaged in ∼27 min. Therefore, ultraviolet metasurface-assisted photoacoustic microscopy is anticipated to benefit intraoperative pathological assessments and basic scientific research by alleviating laborious tissue preparations.