Ink property sensing on a printhead

Patent metadata

Field	Value
Publication number	US-2016339696-A1
Application number	US-201415114967-A
Country	US
Kind code	A1
Filing date	Jan 31, 2014
Priority date	Jan 31, 2014
Publication date	Nov 24, 2016
Grant date	—

Abstract

Ink property sensing on a printhead is described. In an example, a substrate for a printhead includes a cap layer having bores. Chambers are formed beneath the cap layer in fluidic communication with the bores. Fluid ejectors are disposed in at least a portion of the chambers. At least one ion-sensitive field effect transistor (ISFET) is disposed in a respective at least one of the chambers. An electrode is disposed in each of the chambers having an ISFET and capacitively coupled to said ISFET through a dielectric.

First claim

What is claimed is:

1 . A substrate for a printhead, comprising:
a cap layer having bores: chambers formed beneath the cap layer in fluidic communication with the bores; fluid ejectors disposed in at least a portion of the chambers; at least one ion-sensitive field effect transistor (ISFET) disposed in a respective at least one of the chambers; and an electrode disposed in each of the chambers having an ISFET and capacitively coupled to said ISFET through a dielectric.

2 . The substrate of claim 1 , wherein each ISFET comprises:
source and drain diffusion regions in the substrate; a gate region patterned using at least one conductive layer formed on the substrate; and wherein the dielectric includes at least one dielectric layer electrically isolating the gate region from the respective chamber.

3 . The substrate of claim 2 , wherein the at least one conductive layer includes a polysilicon layer and at least one metal layer.

4 . The substrate of claim 2 , wherein the gate region includes a metal region formed in a top-most conductive layer of the at least one conductive layer, the metal region being capacitively coupled with the respective electrode.

5 . The substrate of claim 1 , wherein each electrode is formed on the cap layer above the respective ISFET.

6 . The substrate of claim 2 , wherein each electrode is formed on the dielectric surrounding the ISFET.

7 . A printhead, comprising:
a plurality of nozzles formed in an orifice plate; a plurality of chambers formed in a barrier layer beneath the orifice plate, the plurality of chambers being in fluidic communication with the plurality of nozzles; ink ejectors disposed in at least a portion of the plurality of chambers; and at least one ink property sensor disposed in a respective at least one of the plurality of chambers, each ink property sensor comprising an ion-sensitive field effect transistor (ISFET) capacitively coupled to an electrode through a dielectric.

8 . The printhead of claim 7 , wherein the ISFET of each ink property sensor comprises a floating-gate capactively coupled to the respective electrode through at least one layer of the respective dielectric.

9 . The printhead of claim 7 , wherein the electrode of each ink property sensor is formed on the orifice plate above the respective ISFET.

10 . The printhead of claim 7 , wherein the electrode of each ink property sensor is formed on the respective dielectric surrounding the respective ISFET.

11 . A method of sensing ink properties on a printhead, comprising:
coupling a source of an ion-sensitive field effect transistor (ISFET) formed in a chamber of the printhead containing ink to a reference voltage; coupling a voltage to an electrode in contact with the ink in the chamber, where the electrode is capactively coupled to a gate of the ISFET and the voltage is selected to establish a selected voltage between a drain and the source of the ISFET; and measuring drain-to-source current of the ISFET.

12 . The method of claim 11 , further comprising:
obtaining measurements of the drain-to-source current over a plurality of iterations; and measuring changes in the drain-to-source current over the plurality of iterations.

13 . The method of claim 12 , further comprising:
deriving on concentration measurements from the changes in the drain-to-source current over the plurality of iterations.

Assignees

• Hewlett Packard Development Co Lp

Inventors

• Ge Ning
• Ghozeil Adam L
• Ho Chaw Sing

Classifications

• B41J2/17566

  Ink level or ink residue control · CPC title

• B41J2/1433 Primary

  Structure of nozzle plates · CPC title

• B41J2/195 Primary

  for monitoring ink quality · CPC title

• B41J2/14153

  Structures including a sensor · CPC title

• B41J29/38

  Drives, motors, controls or automatic cut-off devices for the entire printing mechanism · CPC title