Maintenance valve for fluid ejection head

1. An ejection chip comprising:

a substrate that comprises one or more fluid channels and one or more fluid ports, each fluid port being in communication with at least one of the one or more fluid channels;

a flow feature layer disposed over the substrate, the flow feature layer comprising one or more flow features each in communication with at least one of the one or more fluid ports;

a nozzle plate disposed over the flow feature layer, the nozzle plate comprising one or more nozzles each in communication with at least one of the one or more flow features;

one or more fluid paths defined by the one or more fluid channels, the one or more fluid ports, the one or more flow features, and the one or more nozzles; and

one or more valves that change or decrease a gap greater than a clearance spanning a corresponding fluid port of the one or more fluid ports to the clearance upon actuation.

2. The ejection chip of claim 1 , wherein the one or more valves are disposed under the substrate.

3. The ejection chip of claim 1 , wherein the one or more valves are disposed over the substrate.

4. The ejection chip of claim 1 , wherein the one or more valves change or decrease the gap to the clearance to impede flow of fluid through select fluid paths of the one or more fluid paths during a maintenance operation.

5. The ejection chip of claim 1 , wherein the one or more valves change or increase the clearance to the gap to permit fluid flow through select fluid paths of the one or more fluid paths during a jetting operation.

6. The ejection chip of claim 1 , wherein at least one of the one or more valves change or increase the clearance to the gap to selectively permit fluid flow at the one or more fluid ports.

7. The ejection chip of claim 1 , wherein the one or more valves comprise a bimetallic valve.

8. The ejection chip of claim 7 , wherein the bimetallic valve comprises a plurality of materials each having a different coefficient of thermal expansion.

9. The ejection chip of claim 8 , further comprising a heater that heats the bimetallic valve.

10. The ejection chip of claim 7 , wherein the bimetallic valve extends substantially across at least one of the one or more fluid ports.

11. The ejection chip of claim 10 , wherein the bimetallic valve extends entirely across at least one of the one or more fluid ports.

12. The ejection chip of claim 1 , wherein at least one of the one or more valves may be a piezoelectric valve or an electrostatic valve.

13. An ejection chip comprising:

a substrate that comprises one or more fluid channels, one or more fluid ports each in communication with at least one of the one or more fluid channels, and one or more fluid chambers;

a flow feature layer disposed over the substrate, the flow feature layer comprising one or more flow features each in communication with at least one of the one or more fluid ports;

a nozzle plate disposed over the flow feature layer, the nozzle plate comprising one or more nozzles each in communication with at least one of the one or more flow features,

one or more fluid paths defined by the one or more fluid channels, the one or more fluid ports, the one or more flow features, and the one or more nozzles; and

one or more valves that change respective gaps between the one or more fluid channels and the one or more fluid chambers of the substrate.

14. The ejection chip of claim 13 , wherein the one or more valves comprise flexible membranes.

15. The ejection chip of claim 14 , wherein the flexible membranes are formed of an elastomer.

16. The ejection chip of claim 14 , further comprising a pneumatic channel that creates a pressure differential along at least one of the one or more fluid paths.

17. The ejection chip of claim 14 , wherein the flexible membranes engage a wall along at least one of the one or more fluid paths.