Liquid displacement assembly including a fluidic sealing structure

1. A liquid displacement assembly which comprises

a first displacement member;

a second displacement member, the first and second displacement members together defining a volume in which liquid is received, at least one of the first and second displacement members being movable with respect to the other to displace liquid from the volume; and

a sealing formation positioned on each displacement member, the sealing formations being shaped so that a fluidic seal is interposed between the sealing formations when the liquid is received in the volume, each sealing formation having a liquid adhesion surface positioned between side surfaces of the sealing formation and directed towards a plane of reference oriented substantially orthogonally with respect to a direction of relative displacement of the sealing formations, the sealing formations being spaced from each other to define a region in which a meniscus can be formed so that opposed edges of the meniscus adhere to respective adhesion surfaces of the sealing formations and the sealing formations being shaped so that each liquid adhesion surface is interposed between the side surfaces of each respective sealing formation and the plane of reference.

2. A liquid displacement assembly as claimed in claim 1 , which is the product of MEMS-based fabrication process carried out on a wafer substrate.

3. A liquid displacement assembly as claimed in claim 2 , in which the first displacement member includes a wall member that is substantially orthogonal with respect to the substrate, the sealing formation being positioned on the wall member to extend angularly with respect to the wall member so that an included angle of the sealing formation relative to the wall member is less than or equal to 90 degrees.

4. A liquid displacement assembly as claimed in claim 2 , in which the first displacement member includes a wall member that is substantially orthogonal with respect to the substrate, the sealing formation being positioned on the wall member and having a re-entrant transverse profile.

5. A liquid displacement assembly as claimed in claim 4 , in which the sealing formation has a transverse profile that defines a first section that extends outwardly from the wall member, and a second section that extends from the first section towards the substrate.

6. A liquid displacement assembly as claimed in claim 5 , in which the wall member, the first section and the second section are substantially at right angles to each other, with a free end of the second section defining a liquid adhesion surface.

7. A liquid displacement assembly as claimed in claim 2 , in which the second displacement member includes a roof having an ink ejection port defined therein and a wall member that is positioned on the roof member to extend towards the substrate, the sealing formation of the second liquid displacement member being defined by a free end of the wall member.

8. A liquid displacement assembly as claimed in claim 2 , in which the first liquid displacement member includes sidewalls and a roof arranged on the wafer substrate, the roof defining a liquid ejection port, and the second displacement member includes an ejection member that is displaceable towards and away from the substrate to eject liquid from the liquid ejection port.

9. A printhead chip for an ink jet printhead, the printhead chip including

a substrate; and

a plurality of nozzle arrangements positioned on the substrate, each nozzle arrangement comprising

a static ink ejection member positioned on the substrate;

an active ink ejection member, the static and active ink ejection members together defining a nozzle chamber in which ink is received, and the active ink ejection member including a roof that defines an ink ejection port, the active ink ejection member being displaceable towards and away from the substrate to reduce and subsequently enlarge the nozzle chamber so that ink in ejected from the ink ejection port; and

a sealing formation positioned on each ink ejection member, the sealing formations being shaped so that a fluidic seal is interposed between the sealing formations when ink is received in the nozzle chamber, each sealing formation having a liquid adhesion surface positioned between side surfaces of the sealing formation and directed towards a plane of reference oriented substantially orthogonally with respect to a direction of relative displacement of the sealing formations, the sealing formations being spaced from each other to define a region in which a meniscus can be formed so that opposed edges of the meniscus adhere to respective adhesion surfaces of the sealing formations, the sealing formations being shaped so that the liquid adhesion surfaces are interposed between the side surfaces and the plane of reference.

10. A printhead chip for an ink jet printhead, the printhead chip comprising

a substrate; and

a plurality of nozzle arrangements positioned on the substrate, each nozzle arrangement comprising

sidewalls and a roof that are arranged on the substrate, the sidewalls and the roof defining a nozzle chamber with an ink ejection port defined in the roof;

an ink ejection member that is positioned in the nozzle chamber, the ink ejection member being displaceable towards and away from the roof to eject ink from the ink ejection port and the ink ejection member extending through the sidewalls to be connected to an actuator positioned outside of the nozzle chamber; and

at least one sealing formation positioned on the ink ejection member and at least one complementary sealing formation positioned on at least one of the sidewalls and the roof, the sealing formations being shaped so that a fluidic seal is interposed between the, or each sealing formation and the, or each, complementary sealing formation when ink is received in the nozzle chamber, each sealing formation having a liquid adhesion surface positioned between side surfaces of the respective sealing formation and directed towards a plane of reference oriented substantially orthogonally with respect to a direction of relative displacement of the sealing formations, the sealing formations being spaced from each other to define a region in which a meniscus can be formed so that opposed edges of the meniscus adhere to respective adhesion surfaces of the sealing formations, the sealing formations being shaped so that the adhesion surfaces are interposed between the respective side surfaces and the plane of reference.