Phys. Rev. Applied 21, 034056 (2024) – Published 26 March 2024
Artificial active membranes that drive ions up a concentration gradient could pave the way to breakthroughs in numerous fields. This work analyzes the performance of a membrane that utilizes a “flashing” ratchet mechanism to pump ions, accounting for all essential mechanisms governing charge transport. Surprisingly, although driven by electrical fields, both cations and anions are transported in the same direction. This makes the membrane an excellent candidate for distributed water desalination and biomedical applications.
Phys. Rev. Applied 21, 014031 (2024) – Published 18 January 2024
This work studies optically trapped microspheres as flow sensors for the purpose of acoustic transduction in air. While traditional microphones are sensitive to pressure variations and have a peak bandwidth of about 200 kHz, the optically trapped microsphere is sensitive to velocity variations and resolves waveforms with frequency content in the megahertz range. Variations of this method could find applications in near-field acoustic metrology for vibrations, surface waves, and small-scale blast waves; in medicine for ultrasonic imaging in proton cancer therapy; and in bubble-chamber searches for dark matter.
Using fluorescent tracers, researchers visualize the forces that move micrometer-diameter particles through a liquid subjected to a temperature gradient.
H. Gress, J. Barbish, C. Yanik, I.I. Kaya, R.T. Erdogan, M.S. Hanay, M. González, O. Svitelskiy, M.R. Paul, and K.L. Ekinci
Phys. Rev. Applied 20, 044061 (2023) – Published 24 October 2023
The ultimate precision attainable in a mechanical measurement can be determined from the random Brownian motion of the mechanical structure, if the nature of the fluctuations is well understood. To this end, the authors study the Brownian fluctuations of a nanomechanical beam in a viscous fluid. Their predictions based on elasticity theory, fluid dynamics, and statistical mechanics agree well with their experiments, indicating that the observed fluctuations come with “viscous memory”, but no spatial correlations. The insights from this work are expected to impact the design of nanoelectromechanical systems, cantilevers for atomic force microscopy, and other mechanical sensors.
Bo Liu, Randy A. Meijer, Wei Li, Javier Hernandez-Rueda, Hanneke Gelderblom, and Oscar O. Versolato
Phys. Rev. Applied 20, 014048 (2023) – Published 21 July 2023
This article reports experiments on the mass partitioning of a fragmenting liquid sheet, formed after the impact of a nanosecond laser pulse on a tin microdroplet, to help in optimizing mass utilization of the liquid tin that is key to extreme-ultraviolet nanolithography. The authors apply machine learning to analyze subresolution fragments in the temporal evolution of the sheet and its bounding rim, ligaments protruding from the rim, and droplets shed by the ligaments. A full accounting includes the further contributions unique to laser-droplet impact: the mass ablated by the laser, and a surprising, centrally located mass remnant.
Maaike Rump, Uddalok Sen, Roger Jeurissen, Hans Reinten, Michel Versluis, Detlef Lohse, Christian Diddens, and Tim Segers
Phys. Rev. Applied 19, 054056 (2023) – Published 17 May 2023
“Ugh, not again! Something’s wrong with this printer…” In inkjet printing the nozzles in the printhead have intermittent idle periods, during which the ink can evaporate from the nozzle exit. Inks are usually multicomponent, and each component has its own characteristic evaporation rate, resulting in concentration gradients within the ink that can alter the jetting process. Through experiments, analytical modeling, and numerical simulations, the authors unravel the complex physicochemical hydrodynamics associated with the drying of ink at a printhead nozzle.
Synopsis: Mapping the Thermal Forces That Push Particles through Liquids
