Roadmap on Label‐Free Super‐Resolution Imaging

Abstract

Label‐free super‐resolution (LFSR) imaging relies on light‐scattering processes in nanoscale objects without a need for fluorescent (FL) staining required in super‐resolved FL microscopy. The objectives of this Roadmap are to present a comprehensive vision of the developments, the state‐of‐the‐art in this field, and to discuss the resolution boundaries and hurdles that need to be overcome to break the classical diffraction limit of the label‐free imaging. The scope of this Roadmap spans from the advanced interference detection techniques, where the diffraction‐limited lateral resolution is combined with unsurpassed axial and temporal resolution, to techniques with true lateral super‐resolution capability that are based on understanding resolution as an information science problem, on using novel structured illumination, near‐field scanning, and nonlinear optics approaches, and on designing superlenses based on nanoplasmonics, metamaterials, transformation optics, and microsphere‐assisted approaches. To this end, this Roadmap brings under the same umbrella researchers from the physics and biomedical optics communities in which such studies have often been developing separately. The ultimate intent of this paper is to create a vision for the current and future developments of LFSR imaging based on its physical mechanisms and to create a great opening for the series of articles in this field.

Expanding the microbiologist toolbox via new far-red-emitting dyes suitable for bacterial imaging

“…Microbiologists have grappled with the challenge of visualizing bacterial structures since the early days of brightfield microscopy. Despite the historical significance of diffraction-limited, label-free techniques (e.g., phase contrast and DIC), their effectiveness has been hampered by the inability to label specific bacterial subcellular components, thus limiting their role as supportive techniques for label-based ones ( 23 , 47 ). Recent progress has effectively overcome the diffraction barrier, enabling the examination of bacterial cells at the nanoscale without requiring extensive sample manipulation or labeling.…”

“…Recent progress has effectively overcome the diffraction barrier, enabling the examination of bacterial cells at the nanoscale without requiring extensive sample manipulation or labeling. This accomplishment is notably demonstrated through the widespread utilization of atomic force microscopy and its derivatives in bacteriology ( 47 – 51 ). Nevertheless, various label-free techniques have been integrated with diverse label-based microscopies to glean supplementary information ( 18 , 51 – 54 ).…”

Recent Advances and Current Trends in Transmission Tomographic Diffraction Microscopy

“…Consequently, they are, by definition, limited to surface imaging and cannot deliver 3-D images of the interior of transparent samples. The development of far-field optical microscopy with superresolved images is now a very active field (see, for example, [ 310 , 311 , 312 ] and the references therein). In tomographic microscopy, most promising results have been obtained, up to date, in reflection configuration.…”

New Avenues for Phase Imaging: Optical Metasurfaces

“…Given that spatial resolution is a critical performance indicator for any imaging method, especially in biology, we anticipate that approaches to super-resolution imaging will play a significant role in inspiring future metasurface-assisted phase imaging …”