Methods, materials and apparatus for improving control and efficiency of layer-by-layer processes
The disclosure provides materials, apparatuses, and methods for making multilayer coatings with a high degree of efficiency and control. In some aspects, for example, coatings are described having multiple layers of nanoparticles and a polyelectrolyte, wherein the nanoparticles form tightly packed monolayers. The interface between monolayers may include polyelectrolyte material. One or more aspects of such monolayers and interfaces are controllable.
1. A method for depositing a film on a substrate, the method comprising:
(a) depositing a first deposition solution comprising a first deposition material on a substrate to form a first monolayer of said first deposition material;
(b) applying a rinse solution to the first monolayer for a period of time t rinse to form a rinse layer to remove excess first deposition material, wherein t rinse ≦10 seconds;
(c) reducing the thickness of said rinse layer to form a residual rinse layer having a thickness of between 0 microns and 5 microns; and
(c) either:
i) depositing a second deposition solution comprising a second deposition material on said residual rinse layer for a period of time t dep to form a second monolayer of said second deposition material, where said residual rinse layer has a non-zero thickness; or
ii) depositing said second deposition solution comprising said second deposition material on said first monolayer for a period of time t dep to form said second monolayer of said second deposition material, where said residual rinse layer is absent;
wherein t dep ≦−10 seconds;
wherein said first monolayer and said second monolayer form a bilayer.
2. The method of claim 1 , comprising repeating steps (a), (b), (c), and (d) to form a layer by layer assembled film comprising a plurality of bilayers.
3. The method of claim 1 , wherein the residual rinse solution is less than 5 microns but greater than 500 nm in thickness.
4. The method of claim 1 , wherein the first deposition solution and the second deposition solution are applied via a spray process.
5. The method of claim 1 , wherein the formed half bilayer exhibits less than 3% variation in thickness over an area of at least 16 square inches.
6. The method of claim 1 , wherein steps (b) and (c) are repeated z times to further remove unbound deposition material, wherein:
each repeat allows unbound first deposition material to diffuse away from the coating layer; and
each repeat is independently carried out for a period of time t rinse _ x , where z is an integer index.
7. The method of claim 1 , wherein t dep +t rinse <10 seconds.
8. The method of claim 1 , wherein reducing the thickness of said rinse layer comprises application of an air knife, squeegee, nip roller, heat, vacuum, translational movement, ultrasonic energy, magnetic field, electric field, or a combination thereof to said rinse layer.
9. The method of claim 1 , wherein reducing the thickness of the rinse layer is enhanced by addition of one or more additives to the rinse solution.
10. The method of claim 1 , wherein:
the formed bilayer exhibits less than 3% variation in thickness over an area of at least 16 square inches.
11. The method of claim 1 , wherein:
the second deposition solution is deposited via a spray process.
12. The method of claim 1 , wherein:
depositing a second solution comprises depositing said second solution with a thickness (d dep ), wherein d dep is given by:
C s /( C B ·eff)≧ d dep ≧( C s /C B )
and wherein t dep is given by:
t dep >C s 2 /( C B 2 ·D )
wherein:
C s is a desired 2-dimensional concentration per unit area of said second deposition material in said second monolayer;
C B is the bulk concentration per unit volume of said second deposition material in the second deposition solution;
d dep is the thickness of the layer of deposition solution on the surface;
eff is the transfer efficiency of deposition material and is greater than 0.03; and
D is the diffusion coefficient of the second deposition material in the second deposition solution.
13. The method of claim 1 , wherein the first deposition material comprises a polyelectrolyte and the second deposition material comprises nanoparticles.
14. The method of claim 1 , wherein reducing the thickness of said rinse layer comprises removing the rinse layer.
15. The method of claim 12 , wherein C s is the surface concentration based on randomly packed spheres where the areal coverage is between 0.45 and 0.54.