Fluid-bicontinuos particle-stabilised gels

1. A fluid-bicontinuous particle-stabilised gel comprising:

a first fluid and a second fluid which are immiscible within a specific temperature range; and

a stabilising particle layer comprising a continuous layer of stable particles in intimate contact, the particles positioned at a continuous interface between the first fluid and second fluid, wherein the first and second fluid are interpenetrating domains.

2. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the first fluid is hydrophobic and the second fluid is hydrophilic.

3. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein one of the fluids is selected from the group consistoing of an oil, water and an alcohol.

4. A fluid-bicontinuous particle-stabilised gel according to claim 1 , further comprising a strongly fluid asymmetric fluid-bicontinuous state.

5. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the continuous layer of particles comprises partially wetting (PW) particles.

6. A fluid-bicontinuous particle-stabilised gel according to claim 5 , wherein the PW particles are near-neutral wetting (NNW) particles.

7. A fluid-bicontinuous particle-stabilised gel according to claim 6 , wherein the NNW particles have a contact angle between 70 and 110 degrees.

8. A fluid-bicontinuous particle-stabilised gel as claimed in claim 5 , wherein the PW particles are in an arrested state.

9. A fluid-bicontinuous particle-stabilised gel as claimed in claim 5 , wherein the PW particles are magnetically active.

10. A fluid-bicontinuous particle-stabilised gel as claimed in claim 9 , wherein the magnetically active PW particles are superparamagnetic.

11. A fluid-bicontinuous particle-stabilised gel as claimed in claim 5 , wherein the PW particles are electrically conductive.

12. A fluid-bicontinuous particle-stabilised gel as claimed in claim 5 , wherein the PW particles are selected from the group consisting of: silica beads; Janus beads; globular biomolecules; colloidal particles with mixed polymer surfaces comprising flexible chains of two types, A and B, spread across the PW particle surface, wherein A and B are chosen so that A has an affinity for the first fluid, and B has an affinity for the second fluid, or vice versa; spherical micelles, comprising an equal mixture of XZ and YZ block copolymers wherein X has an affinity for the first fluid, and Y has an affinity for the second fluid, or vice versa, and with Z insoluble in both the first and the second fluids; and colloidal particles with micro-heterogeneous wetting properties at different patches on respective surfaces.

13. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the structure of the fluid-bicontinuous particle-stabilised gel comprises a fully ordered, three-dimensional periodic domain.

14. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the structure of the fluid-bicontinuous particle-stabilised gel comprises an amorphous arrangement of two interpenetrating domains.

15. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein further particles, structurants or additives are present in one or both of the first and second fluids.

16. A fluid-bicontinuous particle-stabilised gel according to claim 1 , further comprising particles with attractive interactions.

17. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the particles are in a fluid or aggregated state, within one or both of the first and second fluids.

18. A fluid-bicontinuous particle-stabilised gel according to claim 1 , further comprising emulsion droplets, in a fluid or aggregated state, within one or both of the first and second fluids.

19. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the fluid-bicontinuous particle-stabilised gel comprises a plurality of interpenetrating domains, which comprise a multicontinuous fluid or gel structure, the fluid-bicontinuous particle-stabilised gel being simultaneously permeable to a plurality of mutually immiscible fluids.

20. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the fluid-bicontinuous particle-stabilised gel is insoluble in water and oil based solvents but remains permeable to both oil and water based solvents.

21. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the first fluid and the second fluid are of different refractive index, wherein the first fluid has a refractive index lower than the second fluid, or vice versa.

22. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the fluid-bicontinuous particle-stabilised gel displays thermal conductivity, adjustable by formulation.

23. A fluid-bicontinuous particle-stabilised gel according to claim 1 , wherein the fluid-bicontinuous particle-stabilised gel is adapted to transform to a substantially fluidised state.

24. A fluid-bicontinuous particle-stabilised gel as claimed in claim 23 , wherein the fluidization is reversible.

25. A fluid-bicontinuous particle-stabilised gel as claimed in claim 24 , wherein the fluid-bicontinuous particle-stabilised gel in the reversibly fluidisable state comprises an initial arrested state and a final re-arrested state that the fluid-bicontinuous particle-stabilised gel reverts to.

26. A fluid-bicontinuous particle-stabilised gel as claimed in claim 24 , wherein the fluid-bicontinuous particle-stabilised gel in the reversibly fluidisable state is macroscopically pliable.

27. A fluid-bicontinuous particle-stabilised gel as claimed in claim 24 , wherein the fluid-bicontinuous particle-stabilised gel in the reversibly fluidisable state comprises an initial arrested state, and a final re-arrested state, that have different morphologies.

28. A fluid-bicontinuous particle-stabilised gel as claimed in claim 27 , wherein the re-arrested state comprises droplets, parallel flat layers or cylinders, whose properties on re-arrest are different from the initial arrested state.

29. A method of altering properties of a fluid-bicontinuous particle-stabilised gel comprising the step of using magnetism to alter the properties, the fluid-bicontinuous particle-stabilised gel comprising: a first fluid and a second fluid which are immiscible within a specific temperature range; and a stabilising particle layer comprising a continuous layer of stable particles in intimate contact, the particles positioned at a continuous interface between the first fluid and second fluids and wherein the first and second fluid are interpenetrating domains.

30. A method of altering the properties of a fluid-bicontinuous particle-stabilised gel according to claim 29 , further comprising the steps of:

subjecting the fluid-bicontinuous particle-stabilised gel to a magnetic field, and

removing the particles from the interface using the magnetic field,

wherein the initial fluid-bicontinuous particle-stabilised gel is subsequently rendered entirely fluid by removal of the particles from the interface.

31. A method of making a gel, the method comprising the steps of:

providing PW particles into approximately equal volumes of at least two fluids, at a temperature where the fluids are miscible; and

changing the temperature to one at which the fluids are immiscible, to cause phase separation of the fluids, thereby forming a gel having interpenetrating fluid domains with the PW particles positioned at a continuous interface between the fluids.

32. A method of making a gel according to claim 31 , wherein the phase separation is spinodal decomposition.

33. A method of making a fluid-bicontinuous particle-stabilised gel, comprising the steps of:

dispersing PW particles in a mixture of two solvents by means of mixing, thereby creating a bicontinuous state with more interfacial area than is required to accommodate all of the PW particles, and

stopping the mixing so that the PW particles come into intimate contact on a continuous fluid-fluid interface, precipitating gel formation.

34. A method of making a Janus bead, comprising the steps of:

mixing together approximately equal quantities of spherical micelles comprising XZ and YZ block copolymers, wherein X, Y and Z are polymer chains, in a solution comprising approximately equal volumes of at least two fluids, at a temperature range where the two fluids become miscible, and under such conditions that mixed micelles form spontaneously;

subsequently altering the temperature to a temperature in the temperature range where the fluids are immiscible, causing spinodal decomposition to form a two-phase region, and thereby sequestering the block copolymers at an interface between the fluids;

maintaining a temperature such that the Z polymer chains remain above their glass transition temperature and the XZ and YZ block copolymers migrate to opposite sides of the micelle; and

altering the temperature such that the Z polymer chains pass through their glass transition temperature and the segregated micelle block copolymers are made stable, thus creating particles with hemispheres of opposite wetting properties.

35. A method of making a Janus bead, comprising the steps of:

preparing a fluid-bicontinuous particle-stabilised gel; and

coating substantially one half of the particles in the fluid-bicontinuous particle-stabilised gel with substances that are dissolved in one or both of the first fluids and the second fluids.

36. A generic method of making a gel, comprising the steps of:

dissolving NNW particles in a solution comprising approximately equal volumes of at least two solvents, immiscible at a defined temperature range, at a second temperature range where the two solvents become miscible; and

changing the temperature to a two-phase region where the solvents are immiscible, causing phase separation, thereby sequestering the NNW particles at an interface between the solvents.

37. A generic method of making a fluid-bicontinuous particle-stabilised gel, comprising the steps of:

dispersing NNW particles in a mixture of two solvents by means of mixing, thereby creating a bicontinuous state with more interfacial area than is required to accommodate all of the NNW particles; and

stopping the mixing so that the NNW particles come into intimate contact on a continuous fluid-fluid interface, precipitating gel formation.