Methods of making a printhead

1. A method of forming a printhead, comprising:

providing a body of silicon material,

forming in the body of silicon material at least a portion of a flow path in which fluid is to be pressurized, and

forming in the body of silicon material at least a portion of a deaerator partition between a first region and a second region that are connected by a passageway, the deaerator partition being configured to remove gases or bubbles from the fluid, the first region characterized by a first air pressure and the second region characterized by an air pressure different from the first air pressure.

2. The method of claim 1 , wherein the partition comprises a single layer.

3. The method of claim 1 , wherein the partition comprises two or more layers.

4. The method of claim 1 , wherein a diameter of the passageway is between about 200 nanometers and about 800 nanometers.

5. The method of claim 1 , also comprising roughening a wall of the passageway to form a microstructured surface.

6. The method of claim 1 in which forming the at least a portion of the deaerator partition comprises etching the silicon material to reduce a thickness of the body of the silicon material.

7. The method of claim 1 in which the silicon material comprises a silicon layer and a silicon dioxide layer.

8. The method of claim 7 in which forming the at least a portion of the deaerator partition comprises

etching the silicon layer to the silicon dioxide layer.

9. The method of claim 1 in which the body of silicon material comprises a wetting layer and a silicon layer and forming the at least a portion of the deaerator partition comprises etching the silicon layer to the wetting layer.

10. The method of claim 1 also comprising forming a polymer layer on the body of the silicon material.

11. The method of claim 10 comprising forming the polymer layer by depositing a polymer or a monomer.

12. The method of claim 10 also comprising forming one or more channels through the polymer layer.

13. The method of claim 11 , comprising forming the channels by laser drilling.

14. The method of claim 11 , comprising forming the channels by etching.

15. The method of claim 1 , wherein the first region is in connection with the flow path and the second region is to be connected to a vacuum.

16. The method of claim 1 in which the passageway includes a non-wetting surface.

17. The method of claim 16 , wherein the non-wetting surface is on a side closest to the second region, and the passageway further includes a wetting surface on a side closest to the first region.

18. The method of claim 1 , wherein the passageway is further configured to allow gases and air bubbles to move from a liquid in the first region to the second region when the second region is connected to a vacuum and the vacuum applies a vacuum pressure, P v , in the second region while still preventing liquid from entering the second region.

19. The method of claim 18 , wherein the passageway is cylindrical and has a radius, R, defined by an equation:

R

≤

2

⁢

⁢

(

γ

lv

)

P

v

where γ lv , is a surface energy of a liquid-vapor interface.

20. The method of claim 18 , wherein the passageway is cylindrical and each has a radius, R, defined by an equation:

R

≤

2

⁢

⁢

(

γ

sl

-

γ

sv

)

P

v

where γ sl is a surface energy of a liquid-solid interface, and γ sv is a surface energy of a solid-vapor interface.

21. The method of claim 18 , wherein P v is about 1 atmosphere or less, then a radius of the passageway is about 5 microns or less.

22. The method of claim 1 , wherein the first and second regions and the passageway are configured to prevent a liquid in the first region from entering the second region.