Needles for measurement of body fluid analytes such as glucose

Abstract

Microneedles for analysis of analytes in body fluids may be manufactured from robust materials such as stainless steel by laser cutting at least the basic needle configuration, applying a coating to electrically insulate and/or assure biocompatibility of the needle, and forming electrodes on the needles via lithography or other processes (preferably after treatment of the coated areas at which the electrodes are to be applied). Preferably, the needles have a depression formed therein from which the electrodes extend, and which contains a sensing medium which produces a measurable output in response to the local concentration of the analyte of interest. Thus, when a needle is inserted into the skin such that the depression and its sensing medium encounters body fluids, analyte measurements can be obtained via the electrodes.

What is claimed is: 
     
         1 . A sensor comprising:
 a needle with an insertable portion that is entirely insertable into a body, the insertable portion having a tip, an end opposite the tip, a length measured from the tip to the end opposite the tip, a width measured in a direction perpendicular to the length that is less than the length, and a thickness measured in a direction perpendicular to both the length and the width, wherein the thickness at a free end of the tip is substantially the same as the thickness of at least part of the end opposite the tip; and   a plurality of electrodes each extending from the end opposite the tip towards the tip, wherein at least one of the electrodes has an electrode terminal with a portion closer to the tip than to the end opposite the tip that is attached laterally to the insertable portion.   
     
     
         2 . The sensor of  claim 1 , further comprising a sensing medium configured to generate a response when exposed to one or more specific analytes, wherein the sensing medium covers at least a portion of the electrode terminal. 
     
     
         3 . The sensor of  claim 2 , wherein the insertable portion of the needle defines a depression for holding the sensing medium. 
     
     
         4 . The sensor of  claim 3 , wherein the electrode terminal is also located in the depression. 
     
     
         5 . The sensor of  claim 2 , wherein one of the specific analytes comprises glucose. 
     
     
         6 . The sensor of  claim 2 , wherein the needle comprises a biocompatible metal. 
     
     
         7 . The sensor of  claim 1 , further comprising a mounting tab that extends from the end opposite the tip in a direction away from the tip, the mounting tab having a width greater than the width of the insertable portion, wherein each electrode extends from the insertable portion of the needle to the mounting tab. 
     
     
         8 . The sensor of  claim 1 , wherein the electrodes are adhered laterally to the insertable portion of the needle. 
     
     
         9 . The sensor of  claim 1 , wherein the electrodes are embedded into the insertable portion of the needle. 
     
     
         10 . The sensor of  claim 1 , wherein the electrodes are inseparable from the insertion portion of the needle. 
     
     
         11 . The sensor of  claim 1 , wherein the electrodes are integrally formed with the insertable portion of the needle during manufacture of the insertable portion. 
     
     
         12 . The sensor of  claim 1 , wherein the insertable portion is solid at the end opposite the tip and is free from any recesses that extend axially towards the tip. 
     
     
         13 . A method of manufacturing a sensor comprising a needle with an insertable portion that is entirely insertable into a body, the insertable portion having a tip, an end opposite the tip, a longitudinal axis extending between the tip and the end opposite the tip, a length measured from the tip to the end opposite the tip, a width measured in a direction perpendicular to the longitudinal axis that is less than the length, and a thickness measured in a direction perpendicular to both the length and the width, wherein the thickness at a free end of the tip is substantially the same as the thickness of at least part of the end opposite the tip, and a plurality of electrodes each extending from the end opposite the tip towards the tip, wherein at least one of the electrodes has an electrode terminal with a portion closer to the tip than to the end opposite the tip, the method comprising:
 forming a first part of the insertable portion of the needle; and   applying the electrodes laterally to the first part of the insertable portion of the needle in a direction transverse to the longitudinal axis.   
     
     
         14 . The method of  claim 13 , wherein applying the electrodes laterally to the first part of the insertable portion of the needle comprises adhering the electrodes from a lateral direction onto the first part of the insertable portion of the needle. 
     
     
         15 . The method of  claim 13 , wherein forming the first part of the insertable portion of the needle comprises forming a first insulating layer, and wherein applying the electrodes comprises applying the electrodes on the first insulating layer. 
     
     
         16 . The method of  claim 13 , wherein a depression is formed in the first part of the insertable portion of the needle prior to applying the electrodes, and wherein the electrodes are applied such that the electrode terminal is located in the depression. 
     
     
         17 . The method of  claim 13 , further comprising reinforcing at least some portions of the plurality of electrodes to enhance conductivity and/or increase structural robustness of the at least some portions of the electrodes. 
     
     
         18 . A method of manufacturing a sensor comprising a needle with an insertable portion that is entirely insertable into a body, the insertable portion having a tip, an end opposite the tip, a longitudinal axis extending between the tip and the end opposite the tip, a length measured from the tip to the end opposite the tip, and a width measured in a direction perpendicular to the longitudinal axis that is less than the length, and a plurality of electrodes each extending from the end opposite the tip towards the tip, wherein at least one of the electrodes has an electrode terminal with a first portion closer to the tip than to the end opposite the tip, the method comprising:
 forming a first insulating layer of the insertable portion of the needle;   applying the electrodes laterally onto the first insulating layer of the insertable portion of the needle in a direction transverse to the longitudinal axis; and   forming a second insulating layer over only part of the electrodes without covering at least the first portion of the electrode terminal of the at least one electrode.   
     
     
         19 . The method of  claim 18 , wherein the forming of the second insulating layer comprises forming the second insulating layer over the first portion of the electrode terminal and then forming a depression to expose at least the first portion. 
     
     
         20 . The method of  claim 18 , further comprising reinforcing at least some portions of the plurality of electrodes that are not covered by the second insulating layer to enhance conductivity and/or increase structural robustness of the at least some portions of the electrodes.