Hierarchically structured hydrogel with tunable mechanical properties
View Patent ↗Many embodiments provide methods to produce hydrogels with water content of at least 70% with multi-length-scale hierarchical architecture. The hydrogels have high mechanical stress, high strain, and high toughness. The method includes a pre-concentrating step and a salting-out treatment. The produced hydrogels are anisotropic, comprising micro-sized honeycomb-like pore walls, which in turn comprise interconnected nanofibrils meshes.
1 . A method for fabricating hydrogel comprising:
providing a solution with a solute in a solvent, wherein the solute is capable of aggregation or crystallization by forming hydrogen bonds or via hydrophobic interaction;
concentrating the solution, wherein the concentrated solution forms a first structure with a dimension in micrometer size; and
salting out the concentrated solution in a salt solution to form a hydrogel, wherein the salting out process forms a second structure on the first structure and the second structure has a dimension in nanometer size;
wherein the hydrogel has a hierarchical structure.
2 . The method of claim 1 , wherein the concentrating process is selected from the group consisting of: freezing, freeze-casting, crosslinking, covalent bond-based crosslinking, thermal annealing, phase separation, and polymerization.
3 . The method of claim 2 , wherein the freezing is directional freezing.
4 . The method of claim 3 , wherein the directional freezing forms an anisotropic first structure.
5 . The method of claim 1 , wherein the solute is selected from the group consisting of: a monomer, an oligomer, and a polymer.
6 . The method of claim 1 , wherein the solute is selected from a group consisting of poly(vinyl alcohol) (PVA), poly(2-hydroxylethyl acrylate) (PHEA), gelatin, alginate, and cellulose.
7 . The method of claim 1 , wherein the solute comprises PVA and the salt solution comprises an anion selected from the group consisting of: citrate − , SO 4 2− , CO 3 2− , Ac − , Cl − , NO 3 − , and I − .
8 . The method of claim 1 , wherein the solute comprises PVA and the salt solution comprises a cation selected from the group consisting of: K + , Na + , Cs + , Li + , Ca 2+ , Mg 2+ , and Fe 3+ .
9 . The method of claim 1 , wherein the solvent is water or a water-based solution.
10 . The method of claim 1 , wherein a toughness of the hydrogel is between 0.017 MJ/m 3 and 210 MJ/m 3 .
11 . The method of claim 1 , wherein a strength of the hydrogel is between 50 KPa and 23.5 MPa.
12 . The method of claim 1 , wherein a strain of the hydrogel is between 300% and 2900%.
13 . The method of claim 1 , wherein a water content of the hydrogel is from 70% to 95% weight percent.