Pickering emulsions

The method of any preceding claim, wherein the solvent is selected from N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, isopropanol, acetone, cyclopentanone and cyclohexanone, or a mixture of water and a surfactant.

The method of any preceding claim, wherein the magnitude of the difference between the surface tension of the first liquid phase and the surface tension of the 2D material is within 30 mN/m of the magnitude of the difference between the surface tension of the second liquid phase and the surface tension of the 2D material.

The method of any preceding claim, wherein one of the first and second liquid phases has a surface tension which is from about 5 to about 35 mN/m higher than the surface tension of the 2D material, whilst the other liquid phase has a surface tension which is from about 5 to about 35 mN/m lower than the surface tension of the 2D material.

The method of any preceding claim, wherein the first liquid phase has a surface tension lower than that of the 2D material, and the second liquid phase has a surface tension higher than that of the 2D material.

The method of any preceding claim, wherein the first liquid phase is selected from pentane, hexane, ethyl acetate, cyclohexane, chloroform, dichloromethane, methyl methacrylate, styrene, cyclopentanone, or combinations thereof.

The method of any preceding claim, wherein the second liquid phase is selected from glycerol, water, formamide, diethylene glycol, ethylene glycol, propylene glycol or combinations thereof.

The method of any preceding claim, wherein the particles of 2D material are from 1 to 5 nm thick, and have an average length of from about 50 nm to about 2000 nm.

The method of any preceding claim, wherein the 2D material is graphene, hexagonal boron nitride, phosphorene or a transition metal dichalcogenide, preferably graphene.

The method of any preceding claim, wherein the mixture is homogenized in step (c) by applying high shear forces, ultrasonic mixing, or by the use of a microfluidizer.

The method of any preceding claim, wherein step (c) comprises:

• (c) adding a second liquid phase and homogenising the dispersion of the 2D material in the first liquid phase with the second liquid phase with a microfluidizer to form a Pickering emulsion comprising the first liquid phase, the second liquid phase, and the 2D material, where the average diameter of droplets of the dispersed phase within the emulsion is about 10 μm or less.

The method of any preceding claim, further comprising the step of forming a solid structure from the Pickering emulsion.

A Pickering emulsion stabilised by a non-silicate unfunctionalised 2D material, wherein the 2D material is not graphene or boron nitride.

A Pickering emulsion stabilised by a non-silicate unfunctionalised 2D material, wherein the emulsion comprises a continuous liquid phase and a dispersed liquid phase, wherein the dispersed liquid phase is in the form of droplets having an average diameter of about 50 μm or less.

A Pickering emulsion stabilised by a non-silicate unfunctionalised 2D material, wherein the emulsion comprises a continuous liquid phase and a dispersed liquid phase, and wherein the amount of 2D material present in the emulsion is from about 0.0001 to about 1 vol. %, based on the volume of the dispersed phase.

A liquid strain sensor comprising a Pickering emulsion stabilised by a non-silicate unfunctionalised 2D material, wherein the 2D material is electrically conductive.

Use of a Pickering emulsion stabilised by a non-silicate unfunctionalised 2D material in a strain sensor, wherein the 2D material is electrically conductive.

Use of a Pickering emulsion stabilised by a non-silicate unfunctionalised 2D material as an ink.

A method of printing, comprising applying an ink comprising a Pickering emulsion stabilised by a non-silicate unfunctionalised 2D material to a substrate, and drying the substrate.