Ink jet printhead with suspended heater element

1. An ink jet printhead comprising:

a substrate;

a plurality of chambers supported by the substrate for receiving therewithin bubble forming liquid;

a nozzle aperture formed in a surface of each chamber;

a beam suspended within each chamber, the beam comprising at least an outer heating loop and an inner heating loop, wherein the beam heats at least part of the bubble forming liquid to a temperature above its boiling point to form a gas bubble therein, thereby causing ejection of a drop of the bubble forming liquid through the nozzle aperture corresponding to the beam.

2. The ink jet printhead according to claim 1 , wherein the substrate includes a planar support surface and each chamber comprises:

a planar nozzle plate configured to be parallel to, and spaced apart from, the planar support surface of the substrate; and

depending side walls extending between the support surface and the planar nozzle plate.

3. The ink printhead according to claim 2 , wherein the beam is parallel to both the planar support surface and the planar nozzle plate.

4. The ink jet printhead according to claim 2 , wherein the at least one nozzle plate is less than 10 microns thick.

5. The ink jet printhead according to claim 1 , wherein the ink jet printhead is configured to print on a page and to be a page-width printhead.

6. The ink jet printhead according to claim 1 , wherein each heating loop has two opposite planar sides and is configured such that the gas bubble formed is formed at both of the sides of the heating loop.

7. The ink jet printhead according to claim 1 , wherein each heating loop is substantially covered by a conformal protective coating applied substantially to all sides of the heating loop simultaneously such that the coat is seamless.

8. The ink jet printhead according to claim 1 , wherein each chamber includes an inlet in fluid communication with a supply of bubble forming liquid, wherein as a result of the drop of the bubble forming liquid being ejected, a change of pressure within the chamber is created, thereby causing a portion of the supply of bubble forming liquid to be drawn within the respective chamber.

9. The ink jet printhead according to claim 1 , wherein the beam is suspended so as to be immersed within the bubble forming liquid within the chamber.

10. The ink jet printhead according to claim 1 , wherein the beam is suspended above the bubble forming liquid contained within the chamber.

11. The ink jet printhead according to claim 1 , wherein each chamber receives a supply of bubble forming liquid at an ambient temperature, wherein each heating loop is configured such that the energy required to be applied thereto to heat said part of the bubble forming liquid to cause ejection of said drop is less than the energy required to heat a volume of said bubble forming liquid equal to the volume of the said drop, from a temperature equal to said ambient temperature to said boiling point.

12. The ink jet printhead according to claim 1 wherein the bubble which each heating loop is configured to form is collapsible and has a point of collapse, and wherein each heating loop is configured such that the point of collapse of the bubble formed thereby is spaced from that heating loop.