Nanoalignment by critical Casimir torques
Journal article, 2024
The manipulation of microscopic objects requires precise and controllable forces and torques. Recent advances have led to the use of critical Casimir forces as a powerful tool, which can be finely tuned through the temperature of the environment and the chemical properties of the involved objects. For example, these forces have been used to self-organize ensembles of particles and to counteract stiction caused by Casimir-Liftshitz forces. However, until now, the potential of critical Casimir torques has been largely unexplored. Here, we demonstrate that critical Casimir torques can efficiently control the alignment of microscopic objects on nanopatterned substrates. We show experimentally and corroborate with theoretical calculations and Monte Carlo simulations that circular patterns on a substrate can stabilize the position and orientation of microscopic disks. By making the patterns elliptical, such microdisks can be subject to a torque which flips them upright while simultaneously allowing for more accurate control of the microdisk position. More complex patterns can selectively trap 2D-chiral particles and generate particle motion similar to non-equilibrium Brownian ratchets. These findings provide new opportunities for nanotechnological applications requiring precise positioning and orientation of microscopic objects.
Author
Gan Wang
University of Gothenburg
Piotr Nowakowski
Ruder Boskovic Institute
Max Planck Society
University of Stuttgart
Nima Farahmand Bafi
Polish Academy of Sciences
University of Stuttgart
Max Planck Society
Benjamin Midtvedt
University of Gothenburg
Falko Schmidt
Swiss Federal Institute of Technology in Zürich (ETH)
Agnese Callegari
University of Gothenburg
Ruggero Verre
Chalmers, Microtechnology and Nanoscience (MC2), Nanofabrication Laboratory
Mikael Käll
Chalmers, Physics, Nano and Biophysics
S. Dietrich
Max Planck Society
University of Stuttgart
Svyatoslav Kondrat
University of Stuttgart
Polish Academy of Sciences
Max Planck Society
Giovanni Volpe
University of Gothenburg
Nature Communications
2041-1723 (ISSN) 20411723 (eISSN)
Vol. 15 1 5086Subject Categories
Control Engineering
DOI
10.1038/s41467-024-49220-1