Pablo Palacios-Alonso

arXiv2026

Quantitative measurement of fluid inertial effects in confined Brownian motion

The hydrodynamic response of Brownian particles in liquids is fundamentally altered by inertial forces arising from unsteady momentum transport in the surrounding fluid. These forces are of two distinct types\,: the added mass and the history effect. While both are well understood in bulk and weakly-confined geometries, under deterministic driving, their respective behaviours under strong confinement and thermal fluctuations remain scarcely addressed, unclear and often entangled together. The goal of the present study is thus to fill this fundamental gap. The behaviours of the two distinct inertial contributions are quantitatively investigated in the vicinity of a flat, rigid wall, using a combination of broadrange thermal colloidal-probe atomic-force-microscopy experiments, advanced numerical simulations and theory. The separation of the added-mass and history-force contributions is achieved through their different frequency-scaling signatures within the measured high-resolution thermal spectra. Our results establish a complete picture of Brownian motion at interfaces, in the lubrication regime, with direct relevance to nanofluidics and interfacial biophysics.

cond-mat.soft↗

arXiv2026

Magnetic Nanoparticles as Label-Free Dual-Function Nanoheaters and Nanothermometers

Heat generation and temperature reading at the nanoscale have attracted increasing attention due to their direct relevance in thermal therapeutic approaches. Consequently, huge progress has been made toward the design of dual-function nanoplatforms that integrate heating and thermometry capabilities at the nanoscale. However, in most cases, dual nanoheater nanothermometer platforms rely either on specifically engineered materials or on complex readout schemes, which limits translational potential due to complex implementation procedures. To overcome these challenges, we present a methodology for directly extracting temperature information based on dynamical magnetization measurements of cobalt ferrite magnetic nanoflowers. We demonstrate that these nanocrystals monitor temperature changes through variations in their magnetization cycles measured under alternating magnetic fields. Importantly, this thermometric functionality is preserved after surface functionalization and under chemical variations in the nanoparticle environment. Interestingly, we show that we can simultaneously generate heat and report temperature changes within the same agent. This is thanks to the photothermal conversion of cobalt ferrite nanoparticles subjected to near infrared irradiation and the tight reported relationship between magnetization dynamics and Brownian relaxation. Together, these results establish cobalt ferrite magnetic nanoparticles as a label-free platform for simultaneous heat generation and intrinsic temperature readout, enabling real-time nanoscale thermal control.

physics.bio-ph↗