Direct ink printing of multi-material composite structures

1. A method for fabricating a multi-material composite structure, the method comprising:

forming a first colloidal ink solution comprising a first material matrix, water, and a rheology modifying agent, wherein the first material matrix comprises iron;

forming a second colloidal ink solution comprising a second material matrix, water, and a rheology modifying agent, wherein the second material matrix comprises copper;

printing, by direct ink writing, a first layer on a substrate using a first printing nozzle carrying the first colloidal ink solution;

printing, by direct ink writing, a second layer on top of the first layer using a second printing nozzle carrying the second colloidal ink solution;

forming a 3D structure by printing, by direct ink writing, a plurality of layers comprising the first layer and the second layer printed in an alternating pattern; and

sintering the 3D structure to form the multi-material composite structure, the multi-material composite structure comprising a copper-iron composite structure.

2. The method of claim 1 , wherein forming the first colloidal ink solution further comprises mixing a copper powder with a binding agent and adding a mixture comprising the copper powder and the binding agent to water.

3. The method of claim 2 , wherein forming the first colloidal ink solution further comprises mixing the mixture and the water using a mechanical mixer.

4. The method of claim 2 , wherein mixing the copper powder with the binding agent comprises mixing the copper powder with a layered synthetic nanoclay agent with a chemical formulation of Si8Mg5.45Li0.4O24Na0.7.

5. The method of claim 1 , wherein forming the second colloidal ink solution further comprises mixing an iron powder with a binding agent and adding a mixture comprising the iron powder and the binding agent to water.

6. The method of claim 5 , wherein forming the second colloidal ink solution further comprises mixing the mixture and the water using a mechanical mixer.

7. The method of claim 1 , wherein forming the second colloidal ink solution further comprises mixing a graphene powder with a binding agent and adding a mixture comprising the graphene powder and the binding agent to water.

8. The method of claim 1 , wherein forming the first colloidal ink solution comprises a viscosity between 5 and 500 cP.

9. The method of claim 1 , wherein forming the second colloidal ink solution comprises a viscosity between 5 and 500 cP.

10. The method of claim 1 , wherein forming the first colloidal ink solution comprises a storage modulus between 5 and 500 cP.

11. The method of claim 1 , wherein forming the second colloidal ink solution comprises a storage modulus between 5 and 500 cP.

12. The method of claim 1 , wherein sintering the 3D structure includes curing the 3D structure at a temperature between 40 and 250° C.

13. The method of claim 1 , wherein fabricating the multi-material composite structure comprises a density between 0.8 and 1.5 g/cm 3 .

14. The method of claim 1 , wherein fabricating the multi-material composite structure further comprises a copper-graphene composite structure.

15. The method of claim 1 , wherein sintering the 3D structure to form the multi-material composite structure comprises fabricating sintering the copper-iron composite structure until a copper-iron interface has a hardness of 110 HV.

16. The method of claim 14 , wherein sintering the 3D structure to form the multi-material composite structure comprises sintering the copper-graphene composite structure until a copper-graphene interface has a hardness of approximately 160 HV.