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Cannula assemblies and ambulatory infusion systems with pressure sensors made of stacked coplanar layers

  • US 8,313,468 B2
  • Filed: 03/17/2010
  • Issued: 11/20/2012
  • Est. Priority Date: 03/17/2009
  • Status: Active Grant
First Claim
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1. A cannula assembly comprising a hub and an infusion cannula, the hub comprising a pressure sensor and a fluid channel fluidly coupled to the infusion cannula, wherein the pressure sensor comprises a stack of coplanar layers comprising:

  • a top layer and a base layer, wherein at least a portion of the fluid channel is positioned between the top layer and the base layer;

    an electrode layer positioned between the top layer and the base layer and flexibly coupled to the fluid channel;

    a counter-electrode layer positioned between the top layer and the electrode layer, the counter-electrode layer and electrode layer forming electrodes of a sensing capacitor;

    wherein the top layer is in direct contact on one side with the entire length of the counter-electrode layer and the top layer is substantially the same length as the counter-electrode layer;

    a first spacer layer with a through cut-out such that an electrode cavity is formed between the top layer and the base layer such that the electrode layer extends across the electrode cavity,wherein;

    the electrode layer and the counter-electrode layer are of substantially the same length;

    the first spacer layer prior to the through cut-out is of substantially the same length as the electrode layer and the same length as the counter-electrode layer;

    the electrode, the counter-electrode, and the first spacer layer each have a uniform thickness; and

    a positive fluidic pressure of a fluid in the fluid channel flexes the electrode layer into the electrode cavity thereby modifying a capacitance of the sensing capacitor;

    wherein the electrode layer is in direct contact on one side with the entire length of the electrode cavity and in direct contact with the entire length of the first spacer layer, and the electrode layer is in direct contact on the opposing side with an electrode sealing layer; and

    wherein the electrode sealing layer is in direct contact on one side with the entire length of the electrode layer, and the electrode sealing layer is in direct contact on the opposing side with the fluid channel.

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