Piezoelectric resonator

Abstract

A piezoelectric resonator for use in a sensor arrangement for detecting or measuring an analyte in a medium, comprises a quartz crystal plate, face. The first crystal surface is provided with a first electrode, which has a surface area of less than 15 mm 2 and the second crystal surface is provided with a second electrode. The first electrode may have a rectangular surface shape. A flow cell for use in an apparatus for detecting or measuring an analyte in a medium, comprises walls that form a sensing chamber together with the resonator, and inlet and outlet openings for leading a fluid through the sensing chamber. A part of the resonator constitutes one of the walls of the sensing chamber and is arranged such that the first electrode is situated inside the sensing chamber.

1 . A thickness shear mode piezoelectric resonator for use in a sensor arrangement for detecting or measuring an analyte in a medium, comprising: 
 a quartz crystal plate having a first crystal surface and a second crystal surface, wherein    said first crystal surface comprises a first electrode having a surface area of less than 15 mm 2 ;    said second crystal surface comprises a second electrode.    
   
   
       2 . The resonator of  claim 1 , wherein the surface area of the first electrode is less than 10 mm 2 .  
   
   
       3 . The resonator according to  claim 1 , wherein the surface area of the first electrode is at least 0.05 mm 2 .  
   
   
       4 . The resonator according to  claim 1 , wherein the surface area of the first electrode is smaller than the first crystal surface.  
   
   
       5 . The resonator according to  claim 1 , wherein the distance from the sensing electrode edge to the crystal edge is at least 0.2 mm.  
   
   
       6 . The resonator according to  claim 1 , wherein the first electrode has a rectangular-shaped surface, having a first side and a second side.  
   
   
       7 . The resonator according to  claim 1 , wherein the first side is at least 0.1-10 times as long as the second side.  
   
   
       8 . The resonator according to  claim 1 , wherein 
 the first crystal surface is provided with a first contacting area connected to the first electrode; and    the second crystal surface is provided with a second contacting area connected to the second electrode.    
   
   
       9 . The resonator of  claim 8 , wherein 
 the first electrode has a first side and a second side; and    the first contacting area is connected to the second side of the first electrode.    
   
   
       10 . The resonator according to  claim 1 , wherein the first crystal surface and the second crystal surface are flat.  
   
   
       11 . The resonator according to  claim 1 , wherein the quartz crystal is an inverted mesa.  
   
   
       12 . The resonator of  claim 11 , wherein 
 the quartz crystal plate comprises a first recess having a wall and a bottom surface and a first electrode in the first recess;    the area of the bottom surface is larger than the first electrode; and    the first electrode is arranged in the recess such that there is a distance between the electrode and the recess wall.    
   
   
       13 . The resonator of  claim 11 , wherein the shortest distance from the electrode to the recess wall is at least 0.01 mm.  
   
   
       14 . A flow cell for use in an apparatus for detecting or measuring an analyte in a medium, comprising: 
 a sensing chamber comprised of walls;    a resonator according to  claim 1;  and    inlet and outlet openings for leading a fluid through the sensing chamber, wherein    one of the walls of the sensing chamber consists of a part of the resonator; and    the first electrode of the resonator is inside the sensing chamber.    
   
   
       15 . The flow cell of  claim 14 , wherein a cross sectional area of the sensing chamber perpendicular to a flow direction is less than 2.5 times a cross sectional area of the inlet and outlet openings.  
   
   
       16 . The flow cell of  claim 15 , wherein the cross sectional area of the sensing chamber perpendicular to the flow direction is the same as the cross sectional area of the inlet and outlet openings.  
   
   
       17 . The flow cell according to  claim 14 , wherein the sensing chamber has a volume of less than 2 μl.  
   
   
       18 . The flow cell according to  claim 14 , wherein 
 the flow cell comprises a flow cell element;    the flow cell element includes an outwardly open recess;    the outwardly open recess has a bottom surface and walls    the bottom surface and walls constitute the walls of the sensing chamber not constituted by the resonator;    the resonator is a replaceable part; and    the resonator is held against the flow cell element by a pressing force to cover the recess and form the flow cell.    
   
   
       19 . The flow cell according to  claim 14 , wherein 
 the flow cell comprises a flow cell element;    the flow cell element includes an outwardly open recess;    the outwardly open recess has a bottom surface and walls    the bottom surface and walls constitute the walls of the sensing chamber not constituted by the resonator and    the resonator is attached to the flow cell element by an adhesive to cover the recess and form the flow cell.    
   
   
       20 . The flow cell according to  claim 18 , wherein 
 the flow cell element comprises a contact surface against which the resonator is to be held    the contact surface is plane-parallel to the bottom surface of the outwardly open recess and encircles the recess; and    the recess has a geometrical shape that corresponds to a geometry of the first electrode.    
   
   
       21 . The flow cell according to  claim 18 , wherein the shortest distance from the electrode to the recess walls is at least 0.01 mm.  
   
   
       22 . A sensor arrangement for detecting or measuring an analyte in a medium, comprising a flow cell according to  claim 14 .  
   
   
       23 . A method of sensing or measuring: comprising using a thickness shear mode resonator according to  claim 1  to sense or measure.  
   
   
       24 . The method according to  claim 23 , wherein the resonator is used to sense or measure of liquid samples.  
   
   
       25 . The resonator according to  claim 1 , wherein the surface area of the first electrode is 1-5 mm 2 .  
   
   
       26 . The resonator according to  claim 4 , wherein the first electrode has a surface area that is 0.1-90% of the crystal area.  
   
   
       27 . The resonator according to  claim 5 , wherein the distance from the sensing electrode edge to the crystal edge is at least 1 mm.  
   
   
       28 . The resonator according to  claim 27 , wherein the distance from the sensing electrode edge to the crystal edge is at least 2 mm.