Electrically-conductive patterns for monitoring the filling of medical devices

Abstract

A flexible diagnostic device has a measurement cell that is sandwiched between the conductive surfaces of two conductive-coated insulating layers. At least one of the conductive surfaces is scored with an insulating pattern, so that the flow of a conductive fluid sample into the cell can be monitored.

We claim:  
     
         1 . A medical diagnostic device for measuring an analyte concentration of an electrically conductive biological fluid, comprising a multilayer structure having a first layer and a second layer sandwiching an intermediate layer, 
 a) the first and second layers each comprising an insulating sheet, having a conductive surface adjoining the intermediate layer,    b) the intermediate layer being an insulating layer with a cutout, having a first end and a second end, which, together with the first and second layers, defines a flow channel to permit the sample to flow from the first end to the second end,    c) the flow channel comprising 
 (i) a dry reagent on the conductive surface of one of the layers for reacting with the sample to yield a change in an electrical parameter that can be related to the analyte concentration of the fluid and  
 (ii) an electrochemical cell, within which the electrical parameter is measured,  
   d) the conductive surface of one of the layers having a first insulating pattern scored into its conductive surface to divide the second layer into two regions, insulated from each other, whereby sample that flows across the pattern provides a conductive path from the first end to the second end.    
     
     
         2 . The device of  claim 1 , in which the first end of the cutout is at a first edge of the intermediate layer and the second end is at a second edge of the intermediate layer, opposite the first edge.  
     
     
         3 . The device of  claim 1 , in which the dry reagent is on the conductive surface of the first layer and the insulating pattern is scored into the conductive surface of the second layer.  
     
     
         4 . The device of  claim 1 , in which sample that enters the flow channel at the first end flows through the electrochemical cell, before it reaches the first insulating pattern.  
     
     
         5 . The device of  claim 1 , in which the biological fluid is blood and the analyte being measured is glucose.  
     
     
         6 . The device of  claim 1 , in which the first and second layers each comprise metallized thermoplastic sheets.  
     
     
         7 . The device of  claim 1 , in which the intermediate layer comprises a thermoplastic sheet having adhesive on both surfaces for adhering to the first and second layers.  
     
     
         8 . The device of  claim 1 , in which the reagent on the conductive surface comprises a buffer, a mediator, and an enzyme.  
     
     
         9 . The device of  claim 1 , in which the flow channel is a capillary channel and the insulating pattern scored into the conductive surface has at least one serration within the flow channel.  
     
     
         10 . The device of  claim 9 , in which the insulating pattern has at least one serration within the flow channel pointing toward each end of the channel.  
     
     
         11 . The device of  claim 1 , further comprising a second insulating pattern scored into the conductive surface of the scored layer between the first end and the first insulating pattern to divide the scored layer into three regions, insulated from each other.  
     
     
         12 . The device of  claim 11 , in which sample that enters the flow channel at the first end reaches the second insulating pattern before it flows through the electrochemical cell.  
     
     
         13 . The device of  claim 1 , further comprising electrical circuit means for detecting the flow of fluid through the flow channel.  
     
     
         14 . A method for preparing an electrically-conductive pattern comprising passing a web of a conductive-coated flexible insulator between a cutting die and anvil, in which the cutting die has a cutting element that is raised a height greater than the thickness of the conductive coating for scoring through preselected portions of the conductive coating.  
     
     
         15 . The method of  claim 14 , in which the cutting die and anvil are rollers.  
     
     
         16 . The method of  claim 14 , in which the conductive coating has a thickness in the range from about 5 to about 100 nm and the cutting element is raised about one thousand times the coating thickness.