GB2445163A

GB2445163A - Disposable test strips and associated method for measuring viscosity and density changes in a biological fluid

Info

Publication number: GB2445163A
Application number: GB0626004A
Authority: GB
Inventors: Richard Michael Day
Original assignee: Highland Biosciences Ltd
Current assignee: Highland Biosciences Ltd
Priority date: 2006-12-28
Filing date: 2006-12-28
Publication date: 2008-07-02
Anticipated expiration: 2026-12-28
Also published as: GB2445163B; GB0626004D0

Abstract

A disposable device and method for measuring coagulation times in a fluid, typically blood within a small reaction cell, with the onset of coagulation being determined by measurement of the rate of change or the value, of the frequency of vibration or quality factor of one or more resonating beams. The device includes a lower support member and an upper support member that create a reaction cell. The device also includes at least two members joined at both ends and positioned such that the resonating areas of the members are orientated within the reaction cell. The reagents required to perform a biochemical analysis of the fluid are dispensed on at least one of the inner surfaces of the reaction cell.

Description

Disposable test strips.

Description

This invention relates to a disposable device and method for measuring the viscosity and density properties of a biological liquid More specifically, the invention relates to a disposable testing device that when used with a portable display unit is able to display the results of a coagulation assay. Such a device could be used to measure coagulation of the sample itself or a physical change in a reagent due to species within the sample. An example of an application where coagulation might need to be measured is in management of anti-clotting therapy When the body is injured, damage to the vascular vessels results in a flow of blood To preserve life, the body stops this flow of blood by a biological process known as haemostasis, which causes the formation of a blood clot or thrombosis. Whilst blood clotting is essential for the repair of wounds, thrombosis can occur anywhere within the circulatory system. Thrombosis is a major cause of death due to restricted blood flow to vital organs. A thrombosis that forms within blood vessels of the heart, lungs, brain or limbs can be particularly life threatening causing heart attacks, strokes and deep vein thrombosis Many people who have undergone surgery, suffer from heart disease or are at risk of thrombosis are prescribed drugs to prevent unwanted thrombosis formation within blood vessels An example of such a medication is Warfann. Such medications are highly potent with long-lasting effects, the half-life of this drug in the body is about 2 /2 days Overlap between maintenance doses and the effects of lifestyle and other medications mean that efficient monitoring is cntical to enables management of the dosage. Too little anti-coagulant medication can cause haemorrhaging whilst too little can result in formation of unwanted clotting.

There are a number of clinical tests that are used to routinely assess the levels of anti-coagulant agents in a blood sample One of the most common is the prothrombin time test (PT) The PT test measures how long it takes a sample of blood to clot in the presence of a clotting agent such as Thromboplastin and Ca2. The amount of anti-coagulant present is inversely proportional to the clotting time. Differences in types of Thromboplastin used results in variations in results between equipment manufacturers and labs. To overcome this, the medical field has adopted the Intemationalised Normalised Ratio (INR), to express PT. Another test is the Activated Partial Thromboplastin Test (APTT) A sample of plasma is tested by adding phospholipids, an activator (ellagic acid, kaolin or micronised silica) and Ca2t Formation of Xase and prothrombinase complexes on the surface of the phospholipids enables prothrombin to be converted to thrombin, with subsequent clot formation. The result of this test is the time for clot formation. The APTT test is used to evaluate the intrinsic coagulation pathway, which includes factors 1, II, V, VIII, IX, X, XI and XII, generally performed in a clinical laboratory. The ACT test resembles the APTT test but uses a sample of whole blood Other useful tests have been developed, including immunochemical assays for activation peptide factor IXa, anti-thrombin, Protein C and Protein S

Statement of the Invention

The object of the invention is to provide a disposable apparatus and method capable of measuring clotting times in a whole blood or plasma sample One aspect of this invention provides for a disposable test strip for use in a test meter of the type that receives a disposable test strip and a sample of body fluid and then performs an analysis of the sample to establish the blood clotting time.

Another aspect of the present invention provides a body fluid testing device that detects clotting of a body fluid by means of measuring viscosity and density, and changes in viscosity as a function of time by means of at least two resonating beams joined at both ends Another aspect of the present invention is the means of collecting the sample into the reaction cell and offering it to a resonating mechanism by means of capillary action Reagents for the body fluid coagulation assay are deposited on the inner surface of the reaction cell, and are presented such that they rapidly dissolve and mix with the sample when it Is introduced Exposure of the body fluid sample to reagents cause a controlled reaction that causes the body fluid sample to coagulate At least two resonating beams are mounted within the cell The detection principle provided by this invention is based on the tuning fork When a tuning fork is excited its tines or resonating beams resonate at a certain frequency knov as the fundamental frequency. The fundamental frequency of the tines is dependant on the length, and cross-sectional area as well as the material from which the fork is made fo = (a2 / 2ir12) * (EI/ps) 5 (where, fo is the fundamental or natural frequency, E is the Young's modulus of the material, s is the cross-sectional area of the tine or resonant beam, I is the length of the beam, I is the second moment of the cross-sectional area; a is the value determined by the node; p is the density of the material) Tuning forks can be joined at either one end or both ends The invention uses resonating beams joined at both ends acting as a double-ended tuning fork The benefit over using a single ended tuning fork, cantilever sensor or piezoelectnc crystal (cut to provide surface acoustic waves) is that the damping forces due to fixture of the resonant structures are lower in a double ended tuning fork. The density composition of a body fluid can be found by comparing the resonant beam fundamental frequency in air with the fundamental frequency when the sample has been received by the reaction cell. A further benefit of the resonating beam over a device based on a piezoelectric crystal (cut to provide surface acoustic waves) is that the amplitude of the resonant beam is larger and this amplitude is very sensitive to the density and viscosity of the surrounding medium.

The quality factor is a measure of the "quality" of a resonant system; it is a measure of the sharpness of resonance or frequency selectivity of a resonant vibratory system. In all resonating devices the quality factor is affected by the surroundings As known by anybody skilled in the art, the quality factor of a resonant system changes according to the viscosity of the media it oscillates in However, in a double-ended tuning fork device the quality factor is significantly higher than in piezoelectric devices, giving a much wider dynamic range which allows a single sensor to provide measurement in both air and body fluids that change viscosity during a chemical reaction. As anybody skilled in the art will know that the amplitude of the resonant beam is proportional to the body viscosity; in a low viscosity fluid a resonant beam will oscillate with much higher amplitude over a narrow frequency about its fundamental, compared to a resonant beam in a high viscosity fluid. Introduction of body fluid sample into the reaction cell causes damping of the resonating beams, changes in frequency and quality factor of the resonating beam indicates blood coagulation. The resonating beams are further damped by the Increasing viscosity of the body fluid sample as it coagulates, the damping effect is measured periodically to determine the coagulation of the body fluid as a function of time As anybody skilled in the art will know the walls of the reaction vessel may be orientated closely together to form a capillary. The materials chosen to create the surfaces of the reaction cell have been selected to provide a low surface tension to allow body fluid to fill the reaction cell by capillary action. These materials are selected for enhancing liquid filling whilst not interfering with the reaction. Upon complete filling of the reaction vessel any changes in quality factor and frequency will momentarily stabilise, before further changes take place due to the chemical reaction. The fast response time of the sensor allows for the accurate identification of the time at which body fluid sample was introduced to the reaction cell Alternatively a set of electrodes could be introduced into the reaction cell that when fluid entered the cell electrical contact could be made The resonating beams are formed within a sensor element that can be of any suitable inert material and may be selected from amongst others silicon, gold, platinum or steel. The resonating beams can be formed by etching, laser treatment or by mechanical punching.

The benefit of using resonant members joined at both ends is that damping forces due to the mounting of the resonant members are essentially cancelled Out and thus do not feature in the sensor response. The resonating beams are excited and monitored by means of piezoelectric elements that may be located outside of the reaction cell This is a particular benefit as piezoelectric elements are highly sensitive to changes in temperature Electrical connections are made to these piezoelectric elements by means of patterned conductive layers that form circuits The conductive circuits can be of any suitable conductive matenal and may be selected from amongst others gold, platinum, copper or silver. The conductive layers can be patterned by several methods amongst other others laser ablation, or by screen printing. The conductive layers would serve to connect the piezoelectric elements to the edge of the sensor element A suitable edge connecting receptacle within a test meter could then form a direct electrical path to the piezoelectric elements An additional purpose of the conductive circuit would be to activate the meter in readiness to receive a sample, by means of bridging contacts within the edge connector. Alternatively, as anyone skilled in the art would know, the piezoelectric elements could be excited and! or monitored by non-contact means such as microwave amplitude reflection, light beams or radio frequency.

The separate layers of the test strip could be aligned such that no further trimming would be necessaiy. However, a plurality of devices could be produced and trimmed to size to the desired size and shape of the disposable test strip.

A meter that would accept the test strip would have the ability to display the test results, in addition the meter would apply correction factors needed to take into account any batch to batch variability associated with the disposable test strip manufacture.

Additionally the meter may include a facility to sample environmental conditions such as temperature and apply a correction factor to the measurement response. Additionally the meter would have a memory facility that would enable patients to store previous readings for comparison. The meter may perform an initial self-test on the disposable strip prior to

blood introduction "S

The invention will now be described solely by way of example and with reference to the accompanying drawings.

Brief description of the drawings

Figure 1 depicts schematically resonant beams assemblies that are suitable for measunng properties of a body fluid before and during a chemical reaction. Figure Ia shows a two beam resonant assembly, whilst Figure 1 b shows a three beam resonant assembly at two resonant nodes; Figure 2 depicts typical sensor responses of a resonant beam assembly suitable for measuring properties of a body fluid before and during a chemical reaction; Figure 3 depicts schematically a resonant beam sensing unit and an exploded view of a resonant beam sensing unit that illustrates the components therein, Figure 4 depicts schematically a test strip for determining the coagulation of body fluids and an exploded view of a test strip that illustrates the components therein;

Detailed Description of the invention

Figure Ia and lb show resonant structures that are useful for determining the density and viscosity of a liquid In Figure Ia, a substrate 101 has been machined to form two resonating beam structures (or tines) 102 and 103, attached at both ends. One beam 103 structure is fitted with a piezoelectnc element 104 which in operation causes it to oscillate at its fundamental frequency or a harmonic frequency. A second beam structure 102 being identical to the first beam element 102 oscillates in harmony and is fitted with a piezoelectric "pickup" element 105 which converts the physical movement of the second beam into a measurable signal. The oscillation nodes of the beams are indicated by the dotted line 106. The shape and geometry of the resonant beams 102 and 103, and the exact location of the piezoelectric elements 104 and 105 may be selected to obtain the best sensitivity to changes in body fluid viscosity In Figure 1 b, an alternative triple beam orientation is provided. A substrate 107 has been machined to form three resonating beam structures 108, 109, 110 On a portion of the substrate in proximity and on one side of the three resonating beam structures is a piezoelectrjc drive element 111. The three resonating beam structures are depicted at one oscillation node that would occur when the structure is driven by element 111. On a portion of the substrate in proximity and on the other side of the three resonating beam structures to the piezoelectric drive element 111, is a piezoelectric "pickup" element 112 which converts the physical movement of the second beam into a measurable signal Figure 2 provides artists representations of sensor responses of a resonant beam assembly suitable for measuring properties of a body fluid before and during a chemical reaction Figure 2a depicts the changes in natural frequency of the resonant beam assembly with respect to fluid density 201. Figure 2b depicts changes in amplitude with respect to solution viscosity. The response curve 202 relates to the amplitude of a resonant beam assembly oscillating in air, 203 relates to the amplitude of a resonant beam assembly oscillating in blood, 204 relates to the amplitude of a resonant beam assembly oscillating in a coagulated sample One skilled in the art could calculate the quality factor by measuring the frequency of the peak amplitude divided by the width of the response at half the amplitude.

Figure 3 provides a resonant beam structure suitable for measuring properties of a body fluid before and during a chemical reaction. As shown in Figure 3a, there is provided a triple beam resonant sensor assembly 300 for integration into a disposable test strip. In Figure 3b, there is provided an exploded schematic of a triple beam resonant sensor assembly for integration into a disposable test strip. A substrate 301 is patterned with three resonant structures 302, 303, and 304. These structures may be formed by any conventional method such as laser or chemical etching or stamping. A patterned insulating dielectric layer 305 is disposed onto the patterned substrate 301. This layer may be disposed by any conventional method such as screen printing, ink jet printing.

Alternatively a pre-cast film may be laminated over the substrate 301 Patterned conductive tracks 306 are disposed on the insulating dielectric layer. These conductive tracks may be disposed by any conventional method such as screen pnnting, ink jet printing and can be of any suitably conductive and chemically inert material. A pair of piezoelectric elenienis 307 are disposed onto a portion of the patterned conductive tracks 306, in close proximity to the centre resonant beam 303 A second patterned insulating dielectric layer 308 is disposed onto the patterned substrate 301, to cover the majority of the patterned conductive tracks 306 The second dielectric layer 308 is shorter to expose the ends of the conductive tracks 306. This layer may be disposed by any conventional method such as screen printing, ink jet printing A second set of patterned conductive tracks 309 are disposed over the second dielectnc layer 308 and the piezoelectric elements.

The patterned conductive tracks 306 and 309 may run the length of the substrate, as shown in Figure 3, so that electrical connection can be made between the piezoelectric elements and an external meter via a suitable connector (not shown) In Figure 4a there is a schematic that provides a disposable test strip 400 In Figure 4b, there is an exploded schematic that provides a disposable test strip 400 The disposable test strip 400 comprises, a substrate 401 Onto which is disposed a reagent layer 402.

Alternatively the reagent layer 402 could be disposed on any internal surface of the reaction cell. A first cell forming layer 403 is disposed onto the substrate. This cell forming layer may be formed using a patterned pre-cast film, or by screening printing or ink jet printing a suitable non-reactive polymeric material. A resonant assembly 404 may be laminated over the first cell forming layer. A second cell forming layer 405 is disposed over the resonant assembly 404. A polymeric film 406 is then laminated onto the top of the second cell forming layer. The purpose of film 406 is to provide a upper lid on the reaction vessel arid to protect the underlying structures of the remainder of the test strip from mechanical damage and to improve the stiffness of the disposable test strip The pattern of the first cell forming layer 403 may be of two or more pads arranged to provide a port to allow a sample of body fluid to enter the reaction cell, whilst one or both sides provide a port that may allow for side filling or air escape as liquid enters the reaction cell In operation the test strip would be inserted into a testing meter, such that the contacts on the test strip device (306 and 309 shown in Figure 3) would provide direct electrical connection to the piezoelectric elements Insertion of the test strip into the testing meter would switch on the testing meter, and prepare the system to make a measurement. A small sample of body fluid may be provided either from a tiny wound or from a dropper.

A drop of body would be contacted with the entrance to the open channel and the reaction cell 407 will fill by capillary action and displace the air within it. The change in density of the regions around the resonant beam assembly would trigger the electronics to begin analysing the body fluid sample During a known time period the analysis would be complete and the changes in viscosity and density of the sample before and dunng the reaction are measured After a suitable reaction time has passed an algorithm is used to convert the natural frequency signal and the quality factor measured into a usable test result.

Claims

Claims 1. A sensor for determining the density or viscosity of a

biological sample dunng a chemical reaction comprising a. a substrate; b a reagent layer disposed on the substrate, comprising materials released by the entiy of the sample into the test strip and to react with the sample, c a reaction cell forming element disposed on the substrate; d at least a pair of resonating beam members joined together at each ends, e. at least one member is fitted with a drive element that in operation causes it to oscillate; at least one member is fitted with a detector element that enables the frequency of oscillations to be measured, g. a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell, h. the reaction cell volume is less than 10 microlitres.

2. A sensor according to claim 1, where electric contacts connect the drive and detect elements to an external control unit.

3 A sensor according to claim 2, where an insulating layer over the electrical contacts prevents short circuiting.

4 A sensor according to claim I where a second reaction cell forming element is disposed on the substrate 5. A sensor according to claim 1 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell

II

6. A sensor according to claim 5 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills 7. A sensor according to claim 1, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction 8. A sensor according to claim 1, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction.

9. A sensor according to claim 1, where changes in resonant frequency are used to measure the progress of a chemical reaction A sensor according to claim 1, where changes in amplitude are used to measure the progress of a chemical reaction.

11 A sensor according to claim 1, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 12 A sensor according to claim 1, where the biological sample is blood and the reagents are those required to perform a prothrombin test 13. A sensor according to claim 1, where the reagents include enzymes that create precipitation of the biological fluid.

14. A sensor according to claim 1, where the measured density or viscosity is used to calculate the blood clotting time of the sample A sensor for determining the density or viscosity of a biological sample, before and during a chemical reaction comprising a. a substrate; b. a reagent layer disposed on the substrate, comprising materials released by the entry of the sample into the test stnp and to react with the sample; 12.

c. a reaction cell forming element disposed on the substrate; d at least a pair of resonating beam members joined together at each ends, e at least one member is fitted with a drive element that in operation causes it to oscillate; f at least one member is fitted with a detector element that enables the frequency of oscillations to be measured, g. a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell, h the reaction cell volume is less than 10 microlitres.

16. A sensor according to claim 15, where electnc contacts connect the drive and detect elements to an external control unit.

17 A sensor according to claim 16, where an insulating layer over the electrical contacts prevents short circuiting.

18 A sensor according to claim 15 where a second reaction cell forming element is disposed on the substrate.

19. A sensor according to claim 15 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell.

20. A sensor according to claim 19 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills 21. A sensor according to claim 15, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction.

22. A sensor according to claim 15, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 23. A sensor according to claim 15, where changes in resonant frequency are used to measure the progress of a chemical reaction 24. A sensor according to claim 15, where changes in amplitude are used to measure the progress of a chemical reaction 25. A sensor according to claim 15, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction.

26 A sensor according to claim 1 5, where the biological sample is blood and the reagents are those required to perform a prothrombin test.

27 A sensor according to claim 15, where the reagents include enzymes that create precipitation of the biological fluid 28 A sensor according to claim 15, where the measured density or viscosity is used to calculate the blood clotting time of the sample.

29. A sensor for determining the density or viscosity of a biological sample, during and after a chemical reaction comprising a. a substrate, b. a reagent layer disposed on the substrate, comprising materials released by the entry of the sample into the test strip and to react with the sample, c. a reaction cell forming element disposed on the substrate, d. at least a pair of resonating beam members joined together at each ends; e at least one member is fitted with a drive element that in operation causes it to oscillate, f. at least one member is fitted with a detector element that enables the frequency of oscillations to be measured, g. a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell, h. the reaction cell volume is less than 10 microlities A sensor according to claim 29, where elecinc contacts connect the drive and detect elements to an external control unit.

31. A sensor according to claim 30, where an insulating layer over the electrical contacts prevents short circuiting.

32 A sensor accorchng to claim 29 where a second reaction cell forming element is disposed on the substrate.

33 A sensor according to claim 29 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell 34, A sensor according to claim 33 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills A sensor according to claim 29, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction.

36 A sensor according to claim 29, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 37 A sensor according to claim 29, where changes in resonant frequency are used to measure the progress of a chemical reaction 38 A sensor according to claim 29, where changes in amplitude are used to measure the progress of a chemical reaction. Is

39. A sensor according to claim 29, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction.

40. A sensor according to claim 29, where the biological sample is blood and the reagents are those required to perform a prothrombin test 41 A sensor according to claim 29, where the reagents include enzymes that create precipitation of the biological fluid 42 A sensor according to claim 29, where the measured density or viscosity is used to calculate the blood clotting time of the sample 43. A sensor for determining the density or viscosity of a biological sample, before during and after a chemical reaction comprising a. a substrate; b a reagent layer disposed on the substrate, comprising materials released by the entry of the sample into the test stnp and to react with the sample, c a reaction cell forming element disposed on the substrate; d at least a pair of resonating beam members joined together at each ends, e at least one member is fitted with a drive element that in operation causes it to oscillate; f at least one member is fitted with a detector element that enables the frequency of oscillations to be measured; g a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell; h the reaction cell volume is less than 10 rnicrolitres.

44 A sensor according to claim 43, where electric contacts connect the drive and detect elements to an external control unit I(0 A sensor according to claim 44, where an insulating layer over the electrical contacts prevents short circuiting.

46 A sensor according to claim 43 where a second reaction cell forming element is disposed on the substrate.

47. A sensor according to claim 43 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell.

48 A sensor according to claim 47 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills.

49 A sensor according to claim 43, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction A sensor according to claim 43, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction.

51. A sensor according to claim 43, where changes in resonant frequency are used to measure the progress of a chemical reaction.

52 A sensor according to claim 43, where changes in amplitude are used to measure the progress of a chemical reaction.

53. A sensor according to claim 43, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 54. A sensor according to claim 43, where the biological sample is blood and the reagents are those required to perform a prothrombin test.

55. A sensor according to claim 43, where the reagents include enzymes that create precipitation of the biological fluid.

56 A sensor according to claim 43, where the measured density or viscosity is used to calculate the blood clotting time of the sample 57 A sensor for determining the density and viscosity of a biological sample dunng a chemical reaction comprising: a a substrate, b a reagent layer disposed on the substrate, comprising materials released by the entry of the sample into the test strip and to react with the sample, c. a reaction cell forming element disposed on the substrate; d at least a pair of resonating beam members joined together at each ends, e at least one member is fitted with a drive element that in operation causes it to oscillate, f. at least one member is fitted with a detector element that enables the frequency of oscillations to be measured; g. a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell; h the reaction cell volume is less than 10 microlitres.

58 A sensor according to claim 57, where electric contacts connect the drive and detect elements to an external control unit 59 A sensor according to claim 58, where an insulating layer over the electrical contacts prevents short circuiting.

A sensor according to claim 57 where a second reaction cell forming element is disposed on the substrate.

61 A sensor according to claim 57 vhere the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell.

62. A sensor according to claim 61 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills.

63 A sensor according to claim 57, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction.

64 A sensor according to claim 57, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction.

65, A sensor according to claim 57, where changes in resonant frequency are used to measure the progress of a chemical reaction 66 A sensor according to claim 57, where changes in amplitude are used to measure the progress of a chemical reaction 67 A sensor according to claim 57, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 68 A sensor according to claim 57, where the biological sample is blood and the reagents are those required to perform a prothrombin test.

69. A sensor according to claim 57, where the reagents include enzymes that create precipitation of the biological fluid 70, A sensor according to claim 57, where the measured density and viscosity is used to calculate the blood clotting time of the sample 71. A sensor for determining the density and viscosity of a biological sample, before and during a chemical reaction comprising a. a substrate, b a reagent layer disposed on the substrate, comprising materials released by the entry of the sample into the test stnp and to react with the sample; c. a reaction cell forming element disposed on the substrate; d. at least a pair of resonating beam members joined together at each ends, e at least one member is fitted with a drive element that in operation causes it to oscillate, f at least one member is fitted with a detector element that enables the frequency of oscillations to be measured, g a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell; h. the reaction cell volume is less than 10 microlitres.

72 A sensor according to claim 71, where electric contacts connect the drive and detect elements to an external control unit.

73. A sensor according to claim 72, where an insulating layer over the electrical contacts prevents short circuiting.

74. A sensor according to claim 71 where a second reaction cell forming element is 1 5 disposed on the substrate 75. A sensor according to claim 71 where the hydrophilic suthce is disposed on a lid forming at least a partially closed reaction cell.

76. A sensor according to claim 75 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills 77 A sensor according to claim 71, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction. 2-0

78 A sensor according to claim 71, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 79 A sensor according to claim 71, where changes in resonant frequency are used to measure the progress of a chemical reaction.

A sensor according to claim 71, where changes in amplitude are used to measure the progress of a chemical reaction.

81. A sensor according to claim 71, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 82 A sensor according to claim 71, where the biological sample is blood and the reagents are those required to perform a prothrombin test 83 A sensor according to claim 71, where the reagents include enzymes that create precipitation of the biological fluid 84 A sensor according to claim 71, where the measured density and viscosity is used to calculate the blood clotting time of the sample A sensor for determining the density and viscosity of a biological sample, dunng and after a chemical reaction comprising: a a substrate, b. a reagent layer disposed on the substrate, comprising materials released by the entry of the sample into the test strip and to react with the sample; c a reaction cell forming element disposed on the substrate; d at least a pair of resonating beam members joined together at each ends, e. at least one member is fitted with a drive element that in operation causes it to oscillate; f. at least one member is fitted with a detector element that enables the frequency of oscillations to be measured; g a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell; h. the reaction cell volume is less than 10 microlitres.

86 A sensor according to claim 85, where electnc contacts connect the drive and detect elements to an external control unit.

87 A sensor according to claim 86, where an insulating layer over the electrical contacts prevents short circuiting.

88 A sensor according to claim 85 where a second reaction cell forming element is disposed on the substrate.

89 A sensor according to claim 85 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell 90. A sensor according to claim 89 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills.

91 A sensor according to claim 85, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction.

92 A sensor according to claim 85, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 93. A sensor according to claim 85, where changes in resonant frequency are used to measure the progress of a chemical reaction 94. A sensor according to claim 85, where changes in amplitude are used to measure the progress of a chemical reaction. 2z

A sensor according to claim 85, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 96. A sensor according to claim 85, where the biological sample is blood and the reagents are those required to perform a prothrombin test.

97. A sensor according to claim 85, where the reagents include enzymes that create precipitation of the biological fluid.

98 A sensor according to claim 85, where the measured density and viscosity is used to calculate the blood clotting time of the sample.

99. A sensor for determining the density and viscosity of a biological sample, before during and after a chemical reaction compristng a a substrate; b a reagent layer disposed on the substrate, comprising materials released by the entry of the sample into the test strip and to react with the sample; c. a reaction cell forming element disposed on the substrate, 1 5 d at least a pair of resonating beam members joined together at each ends, e at least one member is fitted with a drive element that in operation causes it to oscillate, f at least one member is fitted with a detector element that enables the frequency of oscillations to be measured; g a hydrophilic surthce disposed on the sensor that enables the sample to fill the reaction cell; h the reaction cell volume is less than 10 microlitres.

100. A sensor according to claim 99, where electric contacts connect the drive and detect elements to an external control unit 101. A sensor according to claim 100, where an insulating layer over the electrical contacts prevents short circuiting.

102 A sensor according to claim 99 where a second reaction cell forming element is disposed on the substrate.

103 A sensor according to claim 99 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell 104. A sensor according to claim 103 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills.

105 A sensor according to claim 99, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction 106 A sensor according to claim 99, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a 1 5 chemical reaction.

107 A sensor according to claim 99, where changes in resonant frequency are used to measure the progress of a chemical reaction.

108. A sensor according to claim 99, where changes in amplitude are used to measure the progress of a chemical reaction.

109. A sensor according to claim 99, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction.

A sensor according to claim 99, where the biological sample is blood and the reagents are those required to perform a prothrombin test 111. A sensor according to claim 99, where the reagents include enzymes that create precipitation of the biological fluid 1 12 A sensor according to claim 99, where the measured density and viscosity is used to calculate the blood clotting time of the sample.

113. A sensor for determining the density or viscosity of a biological sample during a chemical reaction comprising a. a substrate; b a reagent layer disposed on at least one of the resonating beams; c a reaction cell forming element disposed on the substrate; d at least a pair of resonating beam members joined together at each ends; e. at least one member is fitted with a drive element that in operation causes it to oscillate; f at least one member is fitted with a detector element that enables the frequency of oscillations to be measured; g a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell, h the reaction cell volume is less than 10 microlitres 114 A sensor according to claim 113, where electric contacts connect the drive and detect elements to an external control unit 115. A sensor according to claim 114, where an insulating layer over the electrical contacts prevents short circuiting.

1 16 A sensor according to claim 113 where a second reaction cell forming element is disposed on the substrate 117 A sensor according to claim 113 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell.

118 A sensor according to claim 117 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills.

119. A sensor according to claim 113, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction.

A sensor according to claim 113, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 121 A sensor according to claim 113, where changes in resonant frequency are used to measure the progress of a chemical reaction 122 A sensor according to claim 113, where changes in amplitude are used to measure the progress of a chemical reaction.

123. A sensor according to claim 113, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 124. A sensor according to claim 113, where the biological sample is blood and the reagents are those required to perform a prothrombin test.

125. A sensor according to claim 113, where the reagents include enzymes that create precipitation of the biological fluid.

126. A sensor according to claim 113, where the measured density or viscosity is used to calculate the blood clotting time of the sample 127. A sensor for determining the density or viscosity of a biological sample, before and during a chemical reaction comprising a. a substrate; b a reagent layer disposed on at least one of the resonating beams, z'7 c. a reaction cell forming element disposed on the substrate, d. at least a pair of resonating beam members joined together at each ends, e. at least one member is fitted with a drive element that in operation causes it to oscillate, f at least one member is fitted with a detector element that enables the frequency of oscillations to be measured, g a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell, h. the reaction cell volume is less than 10 microlitres.

128. A sensor according to claim 127, where electric contacts connect the dnve and detect elements to an external control unit.

129. A sensor according to claim 128, where an insulating layer over the electrical contacts prevents short circuiting.

130. A sensor according to claim 127 where a second reaction cell forming element is disposed on the substrate.

131 A sensor according to claim 127 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell.

132 A sensor according to claim 131 where there is at least one means of sample entiy to the reaction cell and at least one means of air escape as the reaction cell fills.

133 A sensor according to claim 127, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction. Z7

134. A sensor according to claim 127, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction A sensor according to claim 127, where changes in resonant frequency are used to measure the progress of a chemical reaction 136. A sensor according to claim 127, where changes in amplitude are used to measure the progress of a chemical reaction.

137. A sensor according to claim 127, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 138 A sensor according to claim 127, where the biological sample is blood and the reagents are those required to perform a prothrombin test.

139 A sensor according to claim 127, where the reagents include enzymes that create precipitation of the biological fluid.

140. A sensor according to claim 127, where the measured density or viscosity 1 5 is used to calculate the blood clotting time of the sample 141. A sensor for determining the density or viscosity of a biological sample, during and after a chemical reaction comprising a. a substrate, b a reagent layer disposed on at least one of the resonating beams; c a reaction cell forming element disposed on the substrate, d. at least a pair of resonating beam members joined together at each ends, e. at least one member is fitted with a drive element that in operation causes it to oscillate; 2% f. at least one member is fitted with a detector element that enables the frequency of oscillations to be measured, g. a hydrophilic sur1ce disposed on the sensor that enables the sample to fill the reaction cell; h. the reaction cell volume is less than 10 microlitres 142 A sensor according to claim 141, where electric contacts connect the drive and detect elements to an external control unit.

143. A sensor according to claim 142, where an insulating layer over the electrical contacts prevents short circuiting.

144 A sensor according to claim 141 where a second reaction cell forming element is disposed on the substrate A sensor according to claim 141 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell 146. A sensor according to claim 145 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills 147. A sensor according to claim 141, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction 148. A sensor according to claim 141, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction.

149. A sensor according to claim 141, where changes in resonant frequency are used to measure the progress of a chemical reaction. 2 I

A sensor according to claim 141, where changes in amplitude are used to measure the progress of a chemical reaction.

151 A sensor according to claim 141, where changes in the qualityfactor of the resonating structures are used to measure the progress of a chemical reaction.

1 52. A sensor according to claim 141, where the biological sample is blood and the reagents are those required to perform a prothrombin test.

153 A sensor according to claim 141, where the reagents include enzymes that create precipitation of the biological fluid 154 A sensor according to claim 141, where the measured density or viscosity is used to calculate the blood clotting time of the sample 155. A sensor for determining the density or viscosity of a biological sample, before during and after a chemical reaction comprising a. a substrate; b. a reagent layer disposed on at least one of the resonating beams; c a reaction cell forming element disposed on the substrate; d at least a pair of resonating beam members joined together at each ends; e at least one member is fitted with a drive element that in operation causes it to oscillate; f. at least one member is fitted with a detector element that enables the frequency of oscillations to be measured, g. a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell; h the reaction cell volume is less than 10 microlitres.

1 56. A sensor according to claim 155, where electric contacts connect the drive and detect elements to an external control unit.

157. A sensor according to claim 156, where an insulating layer over the electrical contacts prevents short circuiting.

1 58. A sensor according to claim 155 where a second reaction cell forming element is disposed on the substrate.

159. A sensor according to claim 155 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell.

A sensor according to claim 159 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell tills 161 A sensor according to claim 155, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction.

162. A sensor according to claim 155, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 163. A sensor according to claim 155, where changes in resonant frequency are used to measure the progress of a chemical reaction 164 A sensor according to claim 155, where changes in amplitude are used to measure the progress of a chemical reaction.

A sensor according to claim 155, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 66. A sensor according to claim 1 55, where the biological sample is blood and the reagents are those required to perform a prothrombin test 167. A sensor according to claim 155, where the reagents include enzymes that create precipitation of the biological fluid 168 A sensor according to claim 155, where the measured density or viscosity is used to calculate the blood clotting time of the sample 169 A sensor for determining the density and viscosity of a biological sample during a chemical reaction comprising a. a substrate, b. a reagent layer disposed on at least one of the resonating beams; c a reaction cell forming element disposed on the substrate; d at least a pair of resonating beam members joined together at each ends; e at least one member is fitted with a drive element that in operation causes it to oscillate; f. at least one member is fitted with a detector element that enables the frequency of oscillations to be measured; g a hydrophilic surfce disposed on the sensor that enables the sample to fill the reaction cell, Ii the reaction cell volume is less than 10 microlitres.

A sensor according to claim 169, where electric contacts connect the drive and detect elements to an external control unit.

171. A sensor according to claim 170, where an insulating layer over the electrical contacts prevents short circuiting 172. A sensor according to claim 169 where a second reaction cell forming element is disposed on the substrate.

173. A sensor according to claim 169 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell 174 A sensor according to claim 173 where there is at least one means of sample ently to the reaction cell and at least one means of air escape as the reaction cell fills 175. A sensor according to claim 169, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction 176. A sensor according to claim 169, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 177 A sensor according to claim 169, where changes in resonant frequency are used to measure the progress of a chemical reaction.

178 A sensor according to claim 169, where changes in amplitude are used to measure the progress of a chemical reaction.

1 79 A sensor according to claim 169, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction 180. A sensor according to claim 169, where the biological sample is blood and the reagents are those required to perform a prothrombin test.

181 A sensor according to claim 169, where the reagents include enzymes that create precipitation of the biological fluid.

182. A sensor according to claim 169, where the measured density and viscosity is used to calculate the blood clotting time of the sample.

183. A sensor for determining the density and viscosity of a biological sample, before and during a chemical reaction comprising.

a. a substrate; b. a reagent layer disposed on at least one of the resonating beams, c a reaction cell forming element disposed on the substrate, d at least a pair of resonating beam members joined together at each ends, e. at least one member is fitted with a drive element that in operation causes it to oscillate; f at least one member is fitted with a detector element that enables the frequency of oscillations to be measured; g. a hydrophilic surfice disposed on the sensor that enables the sample to fill the reaction cell; h. the reaction cell volume is less than 10 microlitres 184. A sensor according to claim 183, where electric contacts connect the drive and detect elements to an external control unit.

185. A sensor according to claim 184, where an insulating layer over the electrical contacts prevents short circuiting 186. A sensor according to claim 183 where a second reaction cell forming element is disposed on the substrate 187 A sensor according to claim 183 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell.

188 A sensor according to claim 187 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills. tf-

189 A sensor according to claim 183, where a change in resonant frequency is used to detect when the sensor is filled with sample and mdicate the start of a chemical reaction 190. A sensor according to claim 183, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 191 A sensor according to claim 183, where changes in resonant frequency are used to measure the progress of a chemical reaction 192 A sensor according to claim 183, where changes in amplitude are used to measure the progress of a chemical reaction 193 A sensor according to claim 183, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction.

194 A sensor according to claim 183, where the biological sample is blood and the reagents are those required to perform a prothrombin test 195 A sensor according to claim 183, where the reagents include enzymes that create precipitation of the biological fluid.

196 A sensor according to claim 183, where the measured density and viscosity is used to calculate the blood clotting time of the sample 197 A sensor for determining the density and viscosity of a biological sample, during and after a chemical reaction comprising a. a substrate; b. a reagent layer disposed on at least one of the resonating beams; c. a reaction cell forming element disposed on the substrate; d. at least a pair of resonating beam members joined together at each ends, e at least one member is fitted with a drive element that in operation causes it to oscillate; f. at least one member is fitted with a detector element that enables the frequency of oscillations to be measured; g a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell, h the reaction cell volume is less than 10 microlitres.

198 A sensor according to claim 197, where electric contacts connect the drive and detect elements to an external control unit.

199 A sensor according to claim 198, where an insulating layer over the electrical contacts prevents short circuiting.

200. A sensor according to claim 197 where a second reaction cell forming element is disposed on the substrate.

201, A sensor according to claim 197 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell.

202. A sensor according to claim 201 where there is at least one means of sample ently to the reaction cell and at least one means of air escape as the reaction cell fills.

203. A sensor according to claim 197, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a chemical reaction 204 A sensor according to claim 197, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction 205. A sensor according to claim 197, where changes in resonant frequency are used to measure the progress of a chemical reaction.

206. A sensor according to claim 197, where changes in amplitude are used to measure the progress of a chemical reaction.

207. A sensor according to claim 197, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction.

208. A sensor according to claim 197, where the biological sample is blood and the reagents are those required to perform a prothrombin test 209 A sensor according to claim 197, where the reagents include enzymes that create precipitation of the biological fluid.

210. A sensor according to claim 197, where the measured density and viscosity is used to calculate the blood clotting time of the sample 211. A sensor for determining the density and viscosity of a biological sample, before during and after a chemical reaction comprising: a. a substrate, b a reagent layer disposed on at least one of the resonating beams, c. a reaction cell forming element disposed on the substrate, d at least a pair of resonating beam members joined together at each ends; e at least one member is fitted with a drive element that in operation causes it to oscillate, f. at least one member is fitted with a detector element that enables the frequency of oscillations to be measured, g a hydrophilic surface disposed on the sensor that enables the sample to fill the reaction cell; h. the reaction cell volume is less than 10 microlitres.

212 A sensor according to claim 211, where electric contacts connect the drive and detect elements to an external control unit.

213. A sensor according to claim 212, where an insulating layer over the electrical contacts prevents short circuiting 214. A sensor according to claim 211 where a second reaction cell forming element is disposed on the substrate.

215. A sensor according to claim 211 where the hydrophilic surface is disposed on a lid forming at least a partially closed reaction cell 216 A sensor according to claim 215 where there is at least one means of sample entry to the reaction cell and at least one means of air escape as the reaction cell fills.

217 A sensor according to claim 211, where a change in resonant frequency is used to detect when the sensor is filled with sample and indicate the start of a 1 5 chemical reaction.

218. A sensor according to claim 211, where a change in amplitude is used to detect when the sensor is filled with biological sample and indicate the start of a chemical reaction.

219. A sensor according to claim 211, where changes in resonant frequency are used to measure the progress of a chemical reaction.

220. A sensor according to claim 211, where changes in amplitude are used to measure the progress of a chemical reaction.

221. A sensor according to claim 211, where changes in the quality factor of the resonating structures are used to measure the progress of a chemical reaction.

222. A sensor according to claim 211, where the biological sample is blood and the reagents are those required to perform a prothrombin test 223. A sensor according to claim 211, where the reagents include enzymes that create precipitation of the biological fluid.

224 A sensor according to claim 211, where the measured density and viscosity is used to calculate the blood clotting time of the sample