Asymmetric-detection time-stretch optical microscopy (ATOM) for ultrafast high-contrast cellular imaging in flow

Abstract

Accelerating imaging speed in optical microscopy is often realized at the expense of image contrast, image resolution, and detection sensitivity – a common predicament for advancing high-speed and high-throughput cellular imaging. We here demonstrate a new imaging approach, called asymmetric-detection time-stretch optical microscopy (ATOM), which can deliver ultrafast label-free high-contrast flow imaging with well delineated cellular morphological resolution and in-line optical image amplification to overcome the compromised imaging sensitivity at high speed. We show that ATOM can separately reveal the enhanced phase-gradient and absorption contrast in microfluidic live-cell imaging at a flow speed as high as ~10 m/s, corresponding to an imaging throughput of ~100,000 cells/sec. ATOM could thus be the enabling platform to meet the pressing need for intercalating optical microscopy in cellular assay, e.g. imaging flow cytometry – permitting high-throughput access to the morphological information of the individual cells simultaneously with a multitude of parameters obtained in the standard assay.

Ultrafast time-stretch imaging at 932 nm through a new highly-dispersive fiber

“…The new HDF introduced here can overcome those limitations. The DLR of the new HDF was measured to be ~100 ps/nm per dB at 1060 nm, which is five times better than that of the existing SMFs at this window [24], as shown in Fig. 3(a).…”

“…5. Consequently, a sampling rate of 5 GS/s is sufficient for current time-stretch imaging system at 932 nm, which is almost ten times slower than the previous demonstrations [24]. The field of view (FOV) was measured to be ~190 μm, while a larger FOV can also be achieved by using a wider optical spectrum.…”

“…The field of view (FOV) was measured to be ~190 μm, while a larger FOV can also be achieved by using a wider optical spectrum. Actually, we have also performed time-stretch imaging with the conventional dispersive fiber, i.e., Nufern 1060-xp used in [24], and found it could not resolve the group 7 at the same sampling rate, i.e., 5 GS/s.…”

Time-stretch microscopy on a DVD for high-throughput imaging cell-based assay

“…More significantly, we have demonstrated that this system is compatible with both adherent cell culture and biochemically-specific cell capture assay formats -further enlarging the scope of time-stretch imaging, which has predominately been limited to the suspensioncell format [7,[10][11][12]20]. Furthermore, the single-cell phenotypes extracted from the timestretch images are no longer restricted primarily to biophysical properties, but also the molecular signatures (e.g.…”

“…2(b)). Note that the image contrast can be further enhanced by accessing the phase contrast through the use of interferometry [11,12], or phase gradient contrast by an asymmetric-detection technique [20]. Notably, interferometric time-stretch imaging can further quantify the phase information of cells, from which a set of biophysical phenotypes can be extracted, e.g.…”