Porous particles and methods of making thereof
Provided is a particle that includes a first porous region and a second porous region that differs from the first porous region. Also provided is a particle that has a wet etched porous region and that does have a nucleation layer associated with wet etching. Methods of making porous particles are also provided.
1. A method of making porous particles comprising:
providing a substrate having a surface;
forming a first porous layer in the substrate by electrochemical etching using a first current density;
patterning one or more particles on the substrate;
forming in the substrate a second porous layer having a porosity larger than that of the first porous layer by electrochemical etching using a second current density higher than the first current density; and
releasing the patterned one or more particles from the substrate, wherein the releasing comprises breaking the second porous layer, wherein the released one or more particles contain at least a portion of the first porous layer, and wherein a cross section of an individual particle of the one or more particles has a predetermined regular shape.
2. The method of claim 1 , wherein the substrate is a semiconductor substrate.
3. The method of claim 1 , wherein the substrate is a silicon substrate.
4. The method of claim 1 , wherein the first porous layer is formed before the patterning.
5. The method of claim 1 , wherein said patterning is performed lithographically.
6. The method of claim 1 , wherein a largest dimension of an individual particle of the one or more particles is no more than 5 microns.
7. The method of claim 1 , wherein said predetermined regular shape is an oval.
8. The method of claim 3 , further comprising forming a trench on the silicon substrate before electrochemical etching the silicon substrate such that said trench is formed in a released individual particle of the one or more particles.
9. The method of claim 8 , wherein the trench is positioned on a first porous region of the released individual particle wherein the released individual particle comprises a second porous region in a part of the particle that does not include the trench, and wherein the second porous region differs from the first porous region in at least one property selected from the group consisting of a pore density, a pore size, a pore shape, a pore charge, a pore surface chemistry, and a pore orientation.
10. The method of claim 1 , further chemically modifying a surface of the one or more particles.
11. The method of claim 10 , wherein said chemically modifying is performed prior to said releasing.
12. The method of claim 11 , wherein said chemically modifying modifies a surface of an individual particle of the one or more particles asymmetrically.
13. The method of claim 12 , wherein said chemically modifying comprises filling at least a portion of pores of the first porous layer with a sacrificial material.
14. The method of claim 12 , wherein the chemically modifying comprises at least one of silanizing, oxidizing and antibody conjugating.
15. The method of claim 1 , wherein the first porous layer is a nanoporous layer.
16. The method of claim 1 , wherein a pore size in the first porous layer is no more than 100 nm.
17. The method of claim 1 , wherein an individual particle of the one or more released particles comprises a first porous region and a second porous region that differs from the first region in at least one property selected from the group consisting of a pore density, a pore size, a pore shape, a pore charge, a pore surface chemistry, and a pore orientation.
18. The method of claim 1 , wherein said forming the first porous layer comprises tuning at least one parameter of the first porous layer selected from a thickness, a pore size, porosity, pore orientation and pore shape.
19. The method of claim 1 , wherein said forming the first porous layer comprises forming pores of a predetermined profile in said first porous layer.
20. The method of claim 1 , wherein said releasing comprises exposing the substrate to an ultrasound.
21. The method of claim 1 , further comprising depositing a protective layer on the surface of the substrate.
22. A method of making porous particles comprising:
providing a substrate having a surface;
forming a first porous layer in the substrate by electrochemical etching using a first current density;
patterning one or more particles on the substrate, wherein the first porous layer is formed before the patterning;
forming in the substrate a second porous layer having a porosity larger than that of the first porous layer by electrochemical etching using a second current density higher than the first current density; and
releasing the patterned one or more particles from the substrate, wherein the releasing comprises breaking the second porous layer, and wherein the released one or more particles contain at least a portion of the first porous layer.
23. A method of making porous particles comprising:
providing a substrate having a surface;
forming a first porous layer in the substrate by electrochemical etching using a first current density, wherein said forming the first porous layer comprises forming pores of a predetermined profile in said first porous layer;
patterning one or more particles on the substrate;
forming in the substrate a second porous layer having a porosity larger than that of the first porous layer by electrochemical etching using a second current density higher than the first current density; and
releasing the patterned one or more particles from the substrate, wherein the releasing comprises breaking the second porous layer, and wherein the released one or more particles contain at least a portion of the first porous layer.
24. A method of making porous particles comprising:
providing a substrate having a surface;
forming a first porous layer in the substrate by electrochemical etching using a first current density;
patterning one or more particles on the substrate;
forming in the substrate a second porous layer having a porosity larger than that of the first porous layer by electrochemical etching using a second current density higher than the first current density; and
releasing the patterned one or more particles from the substrate, wherein the releasing comprises breaking the second porous layer, wherein the released one or more particles contain at least a portion of the first porous layer, and wherein a pore size in the first porous layer is no more than 100 nm.