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BP: Fachverband Biologische Physik
BP 9: Single Molecule Biophysics
BP 9.5: Vortrag
Montag, 9. März 2026, 18:00–18:15, BAR/0205
Ultrafast sensing of single nanoparticles with an optofluidic microcavity — •Shalom Palkhivala1, Larissa Kohler1, Christian Ritschel1, Christoph Pauer2, Tim Liedl2, Claus Feldmann1, and David Hunger1 — 1Karlsruhe Institute of Technology, Karlsruhe — 2Ludwig Maximilian University, Munich
The characterisation of single, unlabelled particles in water is of much interest in biophysics and chemistry, where most processes occur in an aqueous environment. We report measurements of single nanoparticles in aqueous suspension using a fibre-based Fabry-Perot microcavity. For quantitative analysis of the nanoparticles’ diffusion dynamics, we developed an analytical autocorrelation function to model diffusion in a standing wave field. This enabled the accurate sizing of nanoparticles having diameters down to 3 nm. [1]
Additionally, the rotational dynamics of anisotropic particles were investigated. Via the polarization modes of the cavity, the orientation of a nanorod was tracked with high temporal resolution (∼ 20 ns), orders of magnitude faster than most other current techniques. As an application of our sensor to biosensing, we demonstrate measurements of individual DNA “origami” structures and of few protein molecules, which already enabled their hydrodynamic sizes to be determined.
We further expect our nanosensor to give an insight into the structural properties and conformation of single bioparticles, and to become a powerful tool for diagnosis in biomedicine and for biochemical and environmental assays.
[1] Palkhivala et al. (2025), ACS Nano, 19, 45, 39320-39326
Keywords: optical microcavity; single nanoparticles; DNA origami; label-free sensing