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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. [ABSTRACT FROM AUTHOR]

We experimentally investigate the collective dynamics in bacterial carpet microfluidic channel. The microfluidic channel is composed of single polar flagellated Vibrio alginolyticus deposited glass substrates. The individual flagellum swimming speed is tuned by varying buffer sodium concentration. Hydrodynamic coupling strength is tuned by varying buffer viscosity. The attached bacteria constantly perform two major modes in flagellum motion, namely, the local rotation and large angle flick. Particle tracking statistics shows high flagellum rotational rate and strong hydrodynamic coupling strength lead to collective sub-diffusive dynamics. The observed effect is strongly correlated to hydrodynamic coupling of flick motions between nearby bacteria. [ABSTRACT FROM AUTHOR]

Interferometric scattering (iSCAT) microscopy is a highly sensitive imaging technique that uses common-path interferometry to detect the linear scattering fields associated with samples. However, when measuring a complex sample, such as a biological cell, the superposition of the scattering signals from various sources, particularly those along the optical axis of the microscope objective, considerably complicates the data interpretation. Herein, we demonstrate high-speed, wide-field iSCAT microscopy in conjunction with confocal optical sectioning. Utilizing the multibeam scanning strategy of spinning disk confocal microscopy, our iSCAT confocal microscope acquires images at a rate of 1,000 frames per second (fps). The configurations of the spinning disk and the background correction procedures are described. The iSCAT confocal microscope is highly sensitive-individual 10 nm gold nanoparticles are successfully detected. Using high-speed iSCAT confocal imaging, we captured the rapid movements of single nanoparticles on the model membrane and single native vesicles in the living cells. Label-free iSCAT confocal imaging enables the detailed visualization of nanoscopic cell dynamics in their most native forms. This holds promise to unveil cell activities that are previously undescribed by fluorescence-based microscopy.

We report the experimental observation of speeded-up collective motion of the monolayer endothelia-cancer mixture on a collagen-coated substrate, after the invasion of a small fraction of motile cancer cells into the confluent endothelial monolayer, through disrupting cell-cell junctions. It is found that, with an increasing waiting time, the cancer-free confluent endothelial monolayer exhibits a dynamical slowing-down of liquidlike micromotion with a gradually decreasing degree of superdiffusion. After invasion, cancer cells aggregate and exhibit turbulentlike cooperative motion, which is enhanced with the increasing size of gradually aggregated cancer clusters, confined by the fluctuating boundaries of surrounding endothelial cells. It, in turn, enhances the surrounding endothelial cell motion and speeds up the originally slowed-down motion.