Christian Rimmbach | Searcharxiv

arXiv2024

When can we see micromotion? Experimental and theoretical analysis of the ChiSCAT scheme

We present an in-depth analysis of ChiSCAT, a recently introduced interferometric microscopy scheme to detect recurring micromotion events in cells. Experimentally, we demonstrate that illumination with low-coherence sources can greatly improve the robustness of the scheme to vibrations. Theoretically, we analyze the performance of ChiSCAT under various noise models, in particular photon shot noise and noise dominated by cellular motions other than the signal. We finally propose ways to improve performance, especially in a setting dominated by cell motions, and conclude with an outlook on potential future directions.

physics.optics↗

arXiv2024

ChiSCAT: unsupervised learning of recurrent cellular micro-motion patterns from a chaotic speckle pattern

There is considerable evidence that action potentials are accompanied by "intrinsic optical signals", such as a nanometer-scale motion of the cell membrane. Here we present ChiSCAT, a technically simple imaging scheme that detects such signals with interferometric sensitivity. ChiSCAT combines illumination by a {\bf ch}aotic speckle pattern and interferometric scattering microscopy ({\bf iSCAT}) to sensitively detect motion in any point and any direction. The technique features reflective high-NA illumination, common-path suppression of vibrations and a large field of view. This approach maximizes sensitivity to motion, but does not produce a visually interpretable image. We show that unsupervised learning based on matched filtering and motif discovery can recover underlying motion patterns and detect action potentials. We demonstrate these claims in an experiment on blebbistatin-paralyzed cardiomyocytes. ChiSCAT promises to even work in scattering tissue, including a living brain.

physics.optics↗