Systems and methods for creation of conducting networks of magnetic particles through dynamic self-assembly process

Abstract

Self-assembly of magnetic microparticles in AC magnetic fields. Excitation of the system by an AC magnetic field provides a variety of patterns that can be controlled by adjusting the frequency and the amplitude of the field. At low particle densities the low-frequency magnetic excitation favors cluster phase formation, while high frequency excitation favors chains and netlike structures. For denser configurations, an abrupt transition to the network phase was obtained.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of one embodiment of the present invention for securing a network of particles on a solid;

FIG. 2 is an illustration of one embodiment of the present invention for securing the network on a surface of a liquid;

FIG. 3 is an illustration of a network generated on the solid interface out of 90 μm nickel spherical particles in an alternating current (AC) magnetic field.

FIG. 4 is an illustration of a network generated on the liquid/air interface out of 45 μm nickel spherical particles in an AC magnetic field.

FIGS. 5 a-c are photographs of structures formed in an external AC magnetic field: rings (5a), compact clusters (5b), and chains of dipoles (5c).

FIGS. 6 a-c are photographs of patterns formed in accordance with the principles of the present invention using nickel spheres (5.3% of the surface monolayer coverage) under magnetic driving at 20 Hz forming a clustered phase (6a), 50 Hz forming a netlike structure (6b), and 100 Hz forming a chain structure (6c);

FIG. 7 a is a graph of the saturated chain length vs frequency of applied 15 Oe AC magnetic field for different amounts of nickel 90 μm particles in the cell, the inset, FIG. 7b showing the saturated chain length vs applied AC (100 Hz) electric voltage applitude for a magnetic driven system (H_max=15 Oe; f=25 Hz; Φ≈0.10);

FIG. 8 are photographs of nickel ink particles with no structuring present (20× magnification); and

FIG. 9 illustrates nickel ink particles after undergoing dynamic self-assembly of the present invention (20× magnification).

Claims

1. An apparatus for assembly of a conducting network of magnetic particles comprising: a cell;a magnet placed around the cell, the magnet producing a magnetic field perpendicular to the container;wherein the magnetic particles assemble into a conducting network in the presence of the magnetic field.

2. The apparatus of claim 1, wherein the cell is positioned between an upper plate and a lower plate.

3. The apparatus of claim 2, wherein the magnetic field is perpendicular to an lower plate.

4. The apparatus of claim 1, wherein the cell is filled with a fluid.

5. The apparatus of claim 4, wherein the magnetic field is perpendicular to an upper surface of the fluid.

6. The apparatus of claim 1, wherein the magnet is an electromagnet.

7. The apparatus of claim 1, wherein the frequency of the magnetic field is a low frequency resulting in the production of clusters.

8. The apparatus of claim 1, wherein the frequency of the magnetic field is an intermediate frequency resulting in the production of netlike patterns.

9. The apparatus of claim 1, wherein the frequency of the magnetic field is high frequency resulting in the production of chains.

10. An apparatus for creation of a conducting network of magnetic particles comprising: a lower plate and a upper plate, the lower and upper plates forming a cell therebetween; anda magnet placed around the periphery of the cell, the magnet producing a magnetic field external to both the upper and lower plates;wherein magnetic particles placed in the cell between a lower plate and an upper plate undergo self-assembly upon magnetic driving.

11. The apparatus of claim 10, wherein the magnet is an electromagnet.

12. The apparatus of claim 10, wherein the frequency of the magnetic field is a low frequency resulting in the production of clusters.

13. The apparatus of claim 12, wherein the frequency is from 0 to about 30 Hz.

14. The apparatus of claim 10, wherein the frequency of the magnetic field is an intermediate frequency resulting in the production of netlike patterns.

15. The apparatus of claim 14, wherein the frequency is from 30 to about 80 Hz.

16. The apparatus of claim 10, wherein the frequency of the magnetic field is high frequency resulting in the production of chains.

17. The apparatus of claim 16, wherein the frequency is from about 80 to about 200 Hz.

18. An apparatus for creation of a conducting network of magnetic particles on a liquid comprising: a cell having a liquid layer for receiving the magnetic particles;a magnet placed around the periphery of the cell, the magnet producing a magnetic field external to both the upper and lower plates;wherein magnetic particles placed in the cell between the magnetic coils undergo self-assembly upon magnetic driving.

19. The apparatus of claim 18, wherein the magnetic field is perpendicular to an upper surface of the liquid.

20. The apparatus of claim 18, herein the frequency of the magnetic field is a low frequency resulting in the production of clusters.