We present analysis tools which are formulated using wide-field interferometric phase microscopy measurements, and show their ability to uniquely quantify the life cycle of live cancer cells. These parameters are based directly on the optical path delay profile of the sample and do not necessitate decoupling the refractive index and the thickness in the cell interferometric phase profile, and thus can be calculated using a single-frame acquisition. To demonstrate the use of these parameters, we have constructed a wide-field interferometric phase microscopy setup and closely traced the full lifecycle of HeLa cancer cells. These initial results show the potential of the parameters to distinguish between the different phases of the cell lifecycle, as well others biological phenomena.

We present a simple-to-align, highly-portable interferometer, which is able to capture wide-field, off-axis interference patterns from transparent samples under low-coherence illumination. This small-dimensions and low-cost device can be connected to the output of a transmission microscope illuminated by a low-coherence source and measure sub-nanometric optical thickness changes in a label-free manner. In contrast to our previously published design, the τ interferometer, the new design is able to fully operate in an off-axis holographic geometry, where the interference fringes have high spatial frequency, and the interference area is limited only by the coherence length of the source, and thus it enables to easily obtain high-quality quantitative images of static and dynamic samples. We present several applications for the new design including nondestructive optical testing of transparent microscopic elements with nanometric thickness and live-cell imaging.

Adipogenesis and increase in fat tissue mass are mechanosensitive processes and hence should be influenced by the mechanical properties of adipocytes. We evaluated subcellular effective stiffnesses of adipocytes using atomic force microscopy (AFM) and interferometric phase microscopy (IPM), and we verified the empirical results using finite element (FE) simulations. In the AFM studies, we found that the mean ratio of stiffnesses of the lipid droplets (LDs) over the nucleus was 0.83 ± 0.14, from which we further evaluated the ratios of LDs over cytoplasm stiffness, as being in the range of 2.5 to 8.3. These stiffness ratios, indicating that LDs are stiffer than cytoplasm, were verified by means of FE modeling, which simulated the AFM experiments, and provided good agreement between empirical and model-predicted structural behavior. In the IPM studies, we found that LDs mechanically distort their intracellular environment, which again indicated that LDs are mechanically stiffer than the surrounding cytoplasm. Combining these empirical and simulation data together, we provide in this study evidence that adipocytes stiffen with differentiation as a result of accumulation of LDs. Our results are relevant to research of adipose-related diseases, particularly overweight and obesity, from a mechanobiology and cellular mechanics perspectives.

We present efficient algorithms for rapid reconstruction of quantitative phase maps from off-axis digital holograms. The new algorithms are aimed at speeding up the conventional Fourier-based algorithm. By implementing the new algorithms on a standard personal computer, while using only a single-core processing unit, we were able to reconstruct the unwrapped phase maps from one megapixel off-axis holograms at frame rates of up to 45 frames per second (fps). When phase unwrapping is not required, the same algorithms allow frame rates of up to 150 fps for one megapixel off-axis holograms. In addition to obtaining real-time quantitative visualization of the sample, the increased frame rate allows integrating additional calculations as a part of the reconstruction process, providing sample-related information that was not available in real time until now. We use these new capabilities to extract, for the first time to our knowledge, the dynamic fluctuation maps of red blood cells at frame rate of 31 fps for one megapixel holograms.

We present a new approach for obtaining significant speedup in the digital processing of extracting unwrapped phase profiles from off-axis digital holograms. The new technique digitally multiplexes two orthogonal off-axis holograms, where the digital reconstruction, including spatial filtering and two-dimensional phase unwrapping on a decreased number of pixels, can be performed on both holograms together, without redundant operations. Using this technique, we were able to reconstruct, for the first time to our knowledge, unwrapped phase profiles from off-axis holograms with 1 megapixel in more than 30 frames per second using a standard single-core personal computer on a MATLAB platform, without using graphic-processing-unit programming or parallel computing. This new technique is important for real-time quantitative visualization and measurements of highly dynamic samples and is applicable for a wide range of applications, including rapid biological cell imaging and real-time nondestructive testing. After comparing the speedups obtained by the new technique for holograms of various sizes, we present experimental results of real-time quantitative phase visualization of cells flowing rapidly through a microchannel.

We present a new interferometric and holographic approach, named interferometry with doubled imaging area (IDIA), with which it is possible to double the camera field of view while performing off-axis interferometric imaging, without changing the imaging parameters, such as the magnification and the resolution. This technique enables quantitative amplitude and phase imaging of wider samples without reducing the acquisition frame rate due to scanning. The method is implemented using a compact interferometric module that connects to a regular digital camera, and is useful in a wide range of applications in which neither the field of view nor the acquisition rate can be compromised. Specifically, the IDIA principle allows doubling the off-axis interferometric field of view, which might be narrower than the camera field of view due to low-coherence illumination. We demonstrate the proposed technique for scan-free quantitative optical thickness imaging of microscopic biological samples, including live neurons and a human sperm cell in rapid motion under high magnification. In addition, we used the IDIA principle to perform non-destructive profilometry during a rapid lithography process of transparent structures.

Label-free IPM can identify sperm cell abnormalities, with an excellent correlation with label-based BFM, and with higher accuracy compared with label-free BFM. Further prospective clinical trials are required to enable IPM as part of clinical sperm selection procedures.

We propose to establish a cancer biomarker based on the unique optical-mechanical signatures of cancer cells measured in a noncontact, label-free manner by optical interferometry. Using wide-field interferometric phase microscopy (IPM), implemented by a portable, off-axis, common-path and low-coherence interferometric module, we quantitatively measured the time-dependent, nanometer-scale optical thickness fluctuation maps of live cells in vitro. We found that cancer cells fluctuate significantly more than healthy cells, and that metastatic cancer cells fluctuate significantly more than primary cancer cells. Atomic force microscopy (AFM) measurements validated the results. Our study shows the potential of IPM as a simple clinical tool for aiding in diagnosis and monitoring of cancer.