arXiv subjects

Marek Piliarik

Publications and source records attributed to Marek Piliarik.

5 recordsLinked to original sources

arXiv2026

Measuring Nanoscale Torques with Cylindrical-Polarization-based Interferometric Scattering Microscopy

The ability to observe rotational dynamics and measure underlying torques is a crucial component in understanding the function and mechanics of nanoscale systems. Yet, direct observation of rotational dynamics at the single-molecule level in liquids remains challenging due to the trade-off between optical detectability and hydrodynamic responsiveness. Labels that are bright enough for rapid readout typically introduce excessive drag, while minimally perturbing probes are difficult to detect at high speed. This limits access to fast rotational dynamics required for direct torque measurements. Here, we introduce cylindrical-polarization-based interferometric scattering microscopy (cypiSCAT), a method encoding the orientation of anisotropic scatterers directly into a single interferometric point spread function, while intrinsically suppressing the isotropic background. We achieve rotational tracking of low-drag orientation labels based on DNA origami-attached gold nanorods with sub-degree angular precision and microsecond temporal resolution, allowing quantitative characterization of nanoscale rotational dynamics. This capability provides direct access to torque metrology at the single-molecule level, here demonstrated through the extraction of optically induced torques as small as ~1 pN nm. Relying on elastic scattering, cypiSCAT combines ultrafast temporal resolution with long observation times, making it well-suited for capturing rapid and rare rotational events and reaction steps in nanoscale biomolecular systems.

physics.optics↗

arXiv2025

Photothermal Fourier-plane Phase Synchronization for Interferometric Scattering Microscopy

We introduce and experimentally implement Fourier-plane phase synchronization for optical microscopy, and demonstrate its performance with interferometric scattering microscopy. By combining a photothermal phase plate and laser beam scanning, we realize a synchronized phase for all scattering components on the Fourier plane of high numerical-aperture microscopes, where the evanescent waves and optical aberration normally produce highly inhomogeneous phase distributions. We achieve an almost perfect point spread function, exhibiting a tighter focus with 50\% enhancement of the signal and ideal circular symmetry. Particularly, by synchronizing the phase to $π/2$, we demonstrate the background speckles exhibit an anti-symmetric dependence on axial defocus, enabling the effective suppression of the speckles via defocus integration and thus the detection of 10 nm particles immobilized on the substrate. The concept and technique of seamless dynamic phase control on the Fourier plane constitute a key asset for modern optical microscopy.

physics.optics↗

arXiv2022

Optical Fingerprint of Flat Substrate Surface and Marker-free Lateral Displacement Detection with Angstrom-level Precision

We report that flat substrates such as glass coverslips with surface roughness well below 0.5 nm feature notable speckle patterns when observed with high-sensitivity interference microscopy. We uncover that these speckle patterns unambiguously originate from the subnanometer surface undulations, and develop an intuitive model to illustrate how subnanometer non-resonant dielectric features could generate pronounced interference contrast in the far field. We introduce the concept of optical fingerprint for the deterministic speckle pattern associated with a particular substrate surface area and intentionally enhance the speckle amplitudes for potential applications. We demonstrate such optical fingerprints can be leveraged for reproducible position identification and marker-free lateral displacement detection with an experimental precision of 0.22 nm. The reproducible position identification allows us to detect new nanoscopic features developed during laborious processes performed outside of the microscope. The demonstrated capability for ultrasensitive displacement detection may find applications in the semiconductor industry and super-resolution optical microscopy.

physics.optics↗

arXiv2020

Multiscale Modeling and Analysis for High-fidelity Interferometric Scattering Microscopy

Interferometric scattering microscopy (iSCAT), as an ultrasensitive fluorescence-free imaging modality, has recently gain enormous attention and been rapidly developing from demonstration of principle to quantitative sensing. Here we report on a theoretical and experimental study for iSCAT with samples having structural dimensions that differ by 4-5 orders of magnitude. In particular, we demonstrate and intuitively explain the profound effects of sub-nanometer surface roughness of a glass coverslip and of a mica surface on the absolute signal and the shape of the point spread function of a gold nanoparticle. These quantities significantly affect the accuracies for determining the target size and position in all three dimensions. Moreover, we investigate a sample system mimicking a gold nanoparticle in a simplified cell environment and show position-dependent and even asymmetric point spread function of the nanoparticle. The multiscale study will facilitate the development of high fidelity iSCAT in real applications.

physics.optics↗

arXiv2013

Direct optical sensing of single unlabeled small proteins and super-resolution microscopy of their binding sites

More than twenty years ago, scientists succeeded in pushing the limits of optical detection to single molecules using fluorescence. This breakthrough has revolutionized biophysical measurements, but restrictions in photophysics and labeling protocols have motivated many efforts to achieve fluorescence-free single-molecule sensitivity in biological studies. Although several interesting mechanisms using vibrational spectroscopy, photothermal detection, plasmonics or microcavities have been proposed for biosensing at the single-protein level, no method has succeeded in direct label-free detection of single proteins. Here, we present the first results using interferometric detection of scattering (iSCAT) from single proteins without the need for any label, optical nanostructure or microcavity. Furthermore, we demonstrate super-resolution imaging of protein binding with nanometer localization precision. The ease of iSCAT instrumentation promises a breakthrough for industrial usage as well as fundamental laboratory experiments.

physics.bio-ph↗