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Small objects floating on a fluid have a tendency to aggregate due to capillary forces. This effect has been used, with the help of a magnetic induction field, to assemble submillimeter metallic spheres into a variety of structures, whose shape and size can be tuned. Under time-varying fields, these assemblies can propel themselves due to a breaking of time reversal symmetry in their adopted shapes. In this article, we study the influence of an in-plane rotation of the magnetic field on these structures. Various rotational modes have been observed with different underlying mechanisms. The magnetic properties of the particles cause them to rotate individually. Dipole-dipole interactions in the assembly can cause the whole structure to align with the field. Finally, non-reciprocal deformations can power the rotation of the assembly. Symmetry plays an important role in the dynamics, as well as the frequency and amplitude of the applied field. Understanding the interplay of these effects is essential, both to explain previous observations and to develop new functions for these assemblies.
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http://dx.doi.org/10.1039/c9sm01414d | DOI Listing |
Proc Natl Acad Sci U S A
September 2025
Molecular Imaging Program at Stanford, Department of Radiology, School of Medicine, Stanford University, Palo Alto, CA 94304.
The biophysical properties of single cells are crucial for understanding cellular function and behavior in biology and medicine. However, precise manipulation of cells in 3-D microfluidic environments remains challenging, particularly for heterogeneous populations. Here, we present "Electro-LEV," a unique platform integrating electromagnetic and magnetic levitation principles for dynamic 3-D control of cell position during separation.
View Article and Find Full Text PDFRev Sci Instrum
September 2025
Department of Nuclear Engineering, University of California, Berkeley, Berkeley, California 94720, USA.
Current and future searches for dark matter axions, based on their resonant conversion to photons in a magnetic field, span many orders of magnitude. A major impediment to designing resonators at the high end of this range, 5 GHz and above, is the proliferation of TE modes, which overwhelm and hybridize with the TM010 mode to which the axion couples, making the search impossible. We demonstrate that a photonic bandgap structure can be designed that completely suppresses the TE spectrum, even reducing the number of lattice periods to two or one and violating perfect lattice symmetry.
View Article and Find Full Text PDFRev Sci Instrum
September 2025
HUN-REN Centre for Energy Research, Budapest, Hungary.
A novel medium-current (up to 20 mA), low normalized beam emittance (<1 π mm mrad) electron cyclotron resonance microwave H+ ion source has been developed at the Center for Energy Research in Budapest, Hungary. This high-stability design targets an energy ripple below 1% while delivering a continuous or pulsed proton beam with adjustable pulse duration (0.1-10 ms) and frequency (0.
View Article and Find Full Text PDFAdv Mater
September 2025
Key Lab of Artificial Micro- and Nano-Structures of Ministry of Education of China, School of Physics and Technology, Wuhan University, Wuhan, 430072, China.
Sequential deposition technique is widely used to fabricate perovskite films with large grain size in perovskite solar cells (PSCs). Residual lead halide (PbI) in the perovskite film tends to be decomposed into metallic lead (Pb) under long-term heating or light soaking. Here, a chiral levetiracetam (LEV) dopant containing α-amide and pyrrolidone groups is introduced into the PbI precursor solution.
View Article and Find Full Text PDFAdv Healthc Mater
September 2025
Energy Storage Institute of Lanzhou University of Technology, School of Materials Science and Engineering, State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou, 730050, China.
The rapid advancement of implantable medical electronic devices has spurred substantial research into implantable energy storage systems. However, the presence of multiple film resistors in traditional sandwich structures impedes further enhancements in the electrochemical performance of supercapacitors and may result in contact failures between electrodes and separators or catastrophic short-circuit failures during tissue deformation. This study introduces a novel approach for fabricating all-in-one Zn-ion hybrid supercapacitors, which effectively mitigates performance degradation and safety concerns arising from interfacial issues.
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