Highly stretchable three-dimensional percolated conductive nano-network structure, method of manufacturing the same, strain sensor including the same and wearable device including the same

1. A method of manufacturing a highly stretchable three-dimensional (3D) percolated conductive nano-network structure, the method comprising:

forming a 3D nano-structured porous elastomer including patterns distributed in a periodic network;

changing a surface of the 3D nano-structured porous elastomer to a hydrophilic state;

conformally adhering a polymeric material on the surface of the 3D nano-structured porous elastomer;

wetting the surface of the 3D nano-structured porous elastomer by infiltrating a conductive solution in which a conductive material is dispersed; and

forming a 3D percolated conductive nano-network coupled with the 3D nano-structured porous elastomer by evaporating a solvent of the conductive solution and removing the polymeric material,

wherein forming the 3D nano-structured porous elastomer includes:

forming a photoresist layer on a substrate;

forming a photoresist pattern having a porous structure by patterning the photoresist layer;

infiltrating a liquid elastomer using the photoresist pattern as a template;

performing a post-treatment on the liquid elastomer; and

obtaining the 3D nano-structured porous elastomer by removing the photoresist pattern.

2. The method of claim 1 , wherein an electrical characteristic of the 3D percolated conductive nano-network is determined based on a number of times of infiltration of the conductive solution.

3. The method of claim 2 , wherein a density of the conductive material included in the 3D percolated conductive nano-network increases and an initial resistance of the 3D percolated conductive nano-network decreases as the number of times of the infiltration of the conductive solution increases.

4. The method of claim 2 , wherein a range of reversible tensile strain in which the electrical characteristic of the 3D percolated conductive nano-network is maintained increases as the number of times of the infiltration of the conductive solution increases.

5. The method of claim 1 , wherein the 3D percolated conductive nano-network is formed along the surface of the 3D nano-structured porous elastomer.

6. The method of claim 1 , wherein the conductive material is based on a material selected from the group consisting of carbon nano-tube (CNT), graphene, silver nanowire, and liquid metal.

7. The method of claim 1 , wherein the 3D nano-structured porous elastomer is formed using a material selected from the group consisting of polydimethylsiloxane (PDMS), PDMS modified urethane acrylate (PUA), perfluoropolyether (PFPE), polyethylene (PE).

8. The method of claim 1 , wherein changing the surface of the 3D nano-structured porous elastomer to the hydrophilic state includes:

performing a plasma treatment or an ultraviolet (UV)/ozone (O 3 ) treatment on the 3D nano-structured porous elastomer.

9. A three-dimensional (3D) percolated conductive nano-network structure, comprising:

a 3D nano-structured porous elastomer including patterns distributed in a periodic network; and

a 3D percolated conductive nano-network including a conductive material and coupled with the 3D nano-structured porous elastomer, and

wherein the 3D percolated conductive nano-network is formed along a surface of the 3D nano-structured porous elastomer,

wherein the 3D nano-structured porous elastomer includes a plurality of layers,

wherein each of the plurality of layers includes the patterns distributed in the periodic network, and

wherein a size of each of a plurality of pores included in each of the plurality of layers is about 1 to 2000 nm.

10. The 3D percolated conductive nano-network structure of claim 9 , wherein:

the 3D percolated conductive nano-network is formed by infiltrating a conductive solution in which the conductive material is dispersed into the 3D nano-structured porous elastomer, and

an electrical characteristic of the 3D percolated conductive nano-network is determined based on a number of times of infiltration of the conductive solution.

11. The 3D percolated conductive nano-network structure of claim 10 , wherein a density of the conductive material included in the 3D percolated conductive nano-network increases and an initial resistance of the 3D percolated conductive nano-network decreases as the number of times of the infiltration of the conductive solution increases.

12. The 3D percolated conductive nano-network structure of claim 10 , wherein a range of reversible tensile strain in which the electrical characteristic of the 3D percolated conductive nano-network is maintained increases as the number of times of the infiltration of the conductive solution increases.

13. The 3D percolated conductive nano-network structure of claim 9 , wherein the conductive material is based on a material selected from the group consisting of carbon nano-tube (CNT), graphene, silver nanowire, and liquid metal.

14. The 3D percolated conductive nano-network structure of claim 9 , further comprising:

buried patterns formed of a material having a refractive index same as that of the 3D nano-structured porous elastomer and configured to fill pores included in the 3D nano-structured porous elastomer.