Gauge invariant and gauge dependent aspects of topological walking colloidal bipeds

Soft Matter ◽  
2021 ◽  
Author(s):  
Mahla Mirzaee-Kakhki ◽  
Adrian Ernst ◽  
Daniel de las Heras ◽  
Maciej Urbaniak ◽  
Feliks Stobiecki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Gauge Invariant ◽  
Magnetic Pattern ◽  
Colloidal Spheres

Paramagnetic colloidal spheres assemble to colloidal bipeds of various length in an external magnetic field and walk on a magnetic pattern.

scholarly journals Simultaneous polydirectional transport of colloidal bipeds

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Mahla Mirzaee-Kakhki ◽  
Adrian Ernst ◽  
Daniel de las Heras ◽  
Maciej Urbaniak ◽  
Feliks Stobiecki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
External Field ◽  
Colloidal Particles ◽  
Addition Reaction ◽  
Lab On A Chip ◽  
Magnetic Pattern ◽  
Colloidal Spheres ◽  
Colloidal Science ◽  
Colloidal Rods

Abstract Detailed control over the motion of colloidal particles is relevant in many applications in colloidal science such as lab-on-a-chip devices. Here, we use an external magnetic field to assemble paramagnetic colloidal spheres into colloidal rods of several lengths. The rods reside above a square magnetic pattern and are transported via modulation of the direction of the external magnetic field. The rods behave like bipeds walking above the pattern. Depending on their length, the bipeds perform topologically distinct classes of protected walks. We design parallel polydirectional modulation loops of the external field that command up to six classes of bipeds to walk on distinct predesigned paths. Using such loops, we induce the collision of reactant bipeds, their polymerization addition reaction to larger bipeds, the separation of product bipeds from the educts, the sorting of different product bipeds, and also the parallel writing of a word consisting of several letters. Our ideas and methodology might be transferred to other systems for which topological protection is at work.

scholarly journals Remarks on inverse electrodynamics

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Patricio Gaete ◽  
José A. Helayël-Neto
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Interaction Energy ◽  
Coulomb Potential ◽  
Nonlinear Electrodynamics ◽  
Gauge Invariant ◽  
Dependent Variables ◽  
Path Dependent ◽  
Formula Type ◽  
Bending Of Light

AbstractWe study physical aspects for a new nonlinear electrodynamics (inverse electrodynamics). It is shown that this new electrodynamics displays the vacuum birefringence phenomenon in the presence of external magnetic field, hence we compute the bending of light. Afterwards we compute the lowest-order modification to the interaction energy within the framework of the gauge-invariant but path-dependent variables formalism. Our calculations show that the interaction energy contains a long-range ($${1 \big / {{r^5}}}$$ 1 / r 5 -type) correction to the Coulomb potential.

Use of Ferrofluid Patterns as Diffusion Masks

2005 ◽  
Vol 877 ◽  
Author(s):  
Derek Halverson ◽  
Ben Yellen ◽  
Sameer Kalghatgi ◽  
Gary Friedman
Keyword(s):  
Magnetic Field ◽  
Porous Media ◽  
External Magnetic Field ◽  
Combinatorial Chemistry ◽  
Aggregate Formation ◽  
Iron Oxide Particles ◽  
Magnetic Pattern ◽  
Field Bias ◽  
Novel Method ◽  
Oxide Particles

AbstractA novel method of dynamically and selectively controlling the diffusion of molecules using aggregation of ferrofluid is proposed. This method can be used to mask specific locations on a surface for combinatorial chemistry or to restrict diffusion of molecules in selected areas in a microfluidic device. This method works by using the controlled aggregation of stabilized 10nm diameter iron oxide particles (ferrofluid) to slow the diffusion of molecules in a similar manner as to how a porous media restricts diffusion. Dynamic aggregate formation is controlled by a magnetic pattern on a substrate in conjunction with an external field. The external magnetic field bias applied to the system causes ferrofluid to aggregate only in designated areas around the magnetic patterns thereby slowing diffusion through the areas where the aggregate clouds have formed.

scholarly journals CONFINING POTENTIAL FROM INTERACTING MAGNETIC AND TORSION FIELDS

2010 ◽  
Vol 25 (06) ◽  
pp. 471-478
Author(s):  
PATRICIO GAETE ◽  
JOSÉ A. HELAŸEL-NETO
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Constant Electric Field ◽  
Static Potential ◽  
Gauge Invariant ◽  
Expectation Value ◽  
Confining Potential ◽  
Dependent Variables ◽  
Path Dependent

Adopting the gauge-invariant but path-dependent variables formalism, we study the coupling of torsion fields with photons in the presence of an external background electromagnetic. We explicitly show that, in the case of a constant electric field strength expectation value, the static potential remains Coulombic, while in the case of a constant magnetic field strength expectation value a confining potential is obtained. This result displays a marked qualitative departure from the usual coupling of axionlike particles with photons in the presence of an external magnetic field.

scholarly journals Reconfigurable assembly of superparamagnetic colloids confined in thermo-reversible microtubes

Soft Matter ◽  
2015 ◽  
Vol 11 (31) ◽  
pp. 6201-6211 ◽  
Author(s):  
Ping Liu ◽  
Julius W. J. de Folter ◽  
Andrei V. Petukhov ◽  
Albert P. Philipse
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Structure Formation ◽  
Colloidal Spheres ◽  
Reconfigurable Assembly

Confinement combined with the application of an external magnetic field results in a switchable structure formation of magnetizable colloidal spheres.

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