GB2366384A

GB2366384A - Simultaneous or sequential measurement of viscous and dielectric material properties using the same sensor element

Info

Publication number: GB2366384A
Application number: GB0021150A
Authority: GB
Inventors: Christopher Barnes; Malcolm John Joyce; Simon Nigel Port; Dean Christopher Ash
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-08-30
Filing date: 2000-08-30
Publication date: 2002-03-06
Anticipated expiration: 2020-08-30
Also published as: GB0021150D0; GB2366384B

Abstract

A method and device for visco-dielectric sensing uses the same sensor element 1, preferably with piezo-electric properties, which has both visco-elastic and dielectric response to a coating or immersion loading a test material 2 to be sensed. An oscillator 3 is driven by a variable voltage source 4 such that the sensing element is excited. An output function from the device allows analysis of parameters having varying weighings and power law dependence. The parameters that can be sensed include the viscosity, h the density, p , the dielectric constant, e , and the surface interaction factor, SF. The output function can involve the impedance, amplitude, frequency or phase. The surface of the sensor may be treated physically or chemically prior to loading of the test material to determine surface wetting or binding forces or to give deposition selectivity. The device may find application in the petrochemical, drinks, food or drug industries.

Description

<Desc/Clms Page number 1> A VISCO-DIELECTRIC SENSING METHOD AND DEVICE This invention relates to a visco-dielectric sensing method and device in which the sensor is a single element capable of responding to or measuring simultaneously or sequentially both the viscous and dielectric properties of a material in any phase.

A single sensor element preferably with piezo -electric property is employed, preferably though not exclusively quartz. Piezo -electric elements have an electrical equivalent circuit which exhibits series and parallel resonance . Their mechanical properties giving rise to the series resonance and their static capacitance giving rise to the parallel resonance . Traditionally such elements have been employed as frequency generators in radio receivers and transmitters or as clocks in digital circuits and computers. They have also been exploited as so called quartz crystal microbalances , where thin films of solid material load the piezoelectric element surface , and in chemical sensors and liquid viscosity monitors. In all the above cases the series resonant mode has been exploited. In this series resonant mode there is no sensitivity to the material dielectric properties whereas in the parallel resonant mode these become significant.

According to the first specific embodiment of this present invention and advantageously for improved material characterization and certain diagnostic applications ,

there is provided a visco-dielectric sensing method and device in which the sensor is a single element is capable of responding to or measuring simultaneously or sequentially both the viscous and dielectric properties of a material in any phase said method comprising the steps of firstly material loading a single sensor element which has preferably piezo -electric properties and secondly exciting the said single sensor element either sequentially at both its series and parallel resonant frequency points or at fixed operating points in between the two or such that it is sequentially stepped or swept across the full frequency width by voltage sweep between the two said resonant points or over a significant part of the range of the said width thereof so as then , in either of the above cases of multiple frequency operation to finally measure the response of the said element this action extracting by direct monitoring of the circuit impedance or by direct or radiative monitoring of the frequency ,amplitude and phase associated with the oscillatory wave-form therefrom or any combination of the three aforesaid wave-form parameters thereof, information concerning both the viscous and dielectric makeup of the said loading material, said information being acquired either sequentially or simultaneously from said single sensor element and where the said material is either in a steady state thermal equilibrium with its surroundings or where it is in a temporal thermally induced or other induced change of state , phase or flux and where the said information obtained allows for the qualitative or quantitative assessment of some characteristic of the physical and /or chemical makeup of the said loading material and/or its ability to interact with or flow upon ,leave by evaporation and/or deposit sub-phase material upon, the surface of the said sensor

element ,governed by such factors as for example; volatility , surface tension , Van der Waals interactions , chemical binding or bonding, molecular weight and size ,density , viscosity , dielectric constant , surface roughness, evaporation dynamics , etc . Further according to this present invention the said loading material can cover all sides and parts of the said sensor element or alternatively only one side or part of the said sensor element is covered and in this second case dielectric coupling from the loading material to the remaining parts of the sensor element may be by or via the fixed static capacitance of the sensor element material itself.

The second specific embodiment of this present invention is a device to bring about the method of visco-dielectric sensing described above, comprising means to coat ,immerse or otherwise deposit the loading material or film or droplet thereof or sub-phase therefrom onto the said sensor element to bring about the said loading and further comprising means to bring about said sequential series and parallel excitation or said sequential or swept excitations at operating points in between by means of voltage steps or sweep and means to monitor the circuit impedance or directly or radiatively monitor the said wave-form frequency ,amplitude or phase or any combination thereof and finally comprising means to extract said viscous and dielectric information therefrom so as to yield the said qualitative or quantitative assessment of said material characteristic and/or any of its surface interactions, as more specifically referred to in the first specific embodiment above , therefrom and /or be used to quantify the amount/type of any sub-phase deposited therefrom .

The invention will now be more particularly described by reference to the drawing in which figure 1 shows the fundamental operation and principal component parts of the device . In figure 1 , 1 is the said single sensor element, 2 is the loading material on or surrounding the element 1 , 3 is the specialist oscillator capable of exciting 1 in its series or parallel resonant mode or at various operating points in between. 4 is the stepped or swept voltage supply and 5 is the output function F(O) . F(0) may be the circuit impedance, Z(w) , the frequency ,w, the phase

or the amplitude, A , related to the oscillation wave-form , but in all these cases , F(O) has at least quadruple functionality with different multiplying coefficients ; a, b ,d, and g and power-law dependencies; 1, m, n, and o respectively , upon the viscosity

the material density

and upon the material dielectric constant and upon a

surface factor, S.F. By manual or automatic adjustment of 4, 3 will become excited at various frequencies between Fs , that of series resonance and Fp , that of parallel resonance and at each successive frequency the relative weightings and power law dependencies of the quadruple dependent variables of F(O) vary in a unique material and surface dependent manner and thus material characterization and /or identification is possible based upon the calculated or observed functionality of this variation. Finally referring to figure 1 , 6 is an optional heating or cooling stage either in contact with 1 or very close to 1 . The present invention in both its specific embodiments is ideally but not exclusively suited to the characterization of small quantities films, sessile layers or droplets preferably though not exclusively mixtures or impure organic solvents such as for example water adulteration of petrol ,

differentiation of DERV from gas oil and kerosene etc and also has perceived uses in the food ,drinks, drugs and isomers in pharmaceutical industry as well as the alcoholic liquor industry for instance, wines ,spirits including for example whisky and whiskey blend checking and differentiation .

There are also uses in determining the age of motor oil whose visco- dielectric properties alter with aging due to thinning by inclusion of unburned fuel and increased electrical conductivity due to inclusion of carbon and metallic particulates. Another aspect of the present invention is that the surface of 1 may be physically and /or chemically modified prior to material loading either to investigate effects of surface wetting and binding forces and/or to encourage selective deposition of solid or liquid chemical sub-phases from the loading material .

Another aspect of the present invention is its use with the optional cooling or heating stage present . When a cooling stage is employed this reduces the evaporation rate when the loading material or part thereof is a small volume , thin layer or film or droplet of volatile solvent in order to lengthen the transient period of study for evaporation dynamics and surface interactions. When the heating stage is employed the reverse effect is achieved bringing about an increase in the evaporation rate of small quantities of non-volatile or low volatility loading materials or parts thereof such as for example, but not exclusively use of the present invention with oils and beverages to advantageously encourage speedier deposition of sub-phase material for quantification o; analysis. Finally those skilled in the art will note that there are further uses of this present invention not explicitly described herein which are nevertheless protected by the scope of the present claims as laid out herein below.

Claims

CLAIMS 1. A visco-dielectric sensing method comprising the steps of loading and exciting a single sensor element is capable of responding to or measuring simultaneously both the viscous and dielectric properties of a material loaded thereupon and measuring the said response.
2. A visco-dielectric sensing method comprising the steps of loading and exciting a single sensor element is capable of responding to or measuring sequentially both the viscous and dielectric properties of a material loaded thereupon and measuring the said response.
3. A sensing method as in claim 1 above in which the said single element is piezoelectric or has piezoelectric properties .
4. A sensing method as in claim 2 above in which the said single element is piezoelectric or has piezoelectric properties .
5. A visco-dielectric sensing method as in claims 3 or 4 above comprising the steps of firstly material loading the single sensor element secondly exciting the said single sensor element sequentially at both its series and parallel resonant frequency points thereof so multiple frequency operation allows extraction of by direct monitoring of the circuit impedance or by direct or radiative monitoring of the frequency ,amplitude and phase

<Desc/Clms Page number 7>

associated with the wave-form therefrom or any combination of the three aforesaid wave-form parameters thereof ,information concerning both the viscous and dielectric makeup of the said loading material, where the said material is either in a steady state thermal equilibrium with its surroundings or where it is in a temporal thermally induced or other induced change of state , phase or flux and where the said information obtained allows for the qualitative or quantitative assessment of some characteristic of the physical and /or chemical makeup of the said loading material and/or its ability to interact with or flow upon ,leave by evaporation and/or deposit sub-phase material upon , the surface of the said sensor element ,governed by such factors as for example; volatility , surface tension , Van der Waals interactions, chemical binding or bonding, molecular weight and size density, viscosity , dielectric constant , surface roughness, evaporation dynamics , etc., further accordingly, the said loading material can cover all sides and parts of the said sensor element or alternatively only one side or part of the said sensor element is covered and in this second case dielectric coupling may be by fixed static capacitance of the piezoelectric material itself to the uncovered parts of the sensor element .
6. A method as in claim 5 above wherein the said waveform is oscillatory .
7. A method as in claim 5 or 6 above wherein the said piezoelectric element is excited at some fixed operating points in between the series and parallel resonant points .

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8. A Method as in claim 5 or 6 above except in that the said element is excited by being sequentially stepped or swept across the full frequency width between the series and parallel resonant points by means of a voltage step or sweep . 9. A method in claim 5 or 6 and 8 above with voltage steps or sweep between two operating points over a significant part of the frequency width range between the series and parallel resonant points . 10. A device to bring about the method of visco-dielectric sensing described in any of claims 1-9 above , comprising means to coat ,immerse or otherwise deposit the loading material or film or droplet thereof or sub-phase therefrom onto the said sensor element to bring about said loading further comprising means to bring about said sequential series and parallel excitation or said sequential or swept excitations at operating points in between by means of voltage steps or sweep and means to monitor the circuit impedance or directly or radiatively monitor the said wave-form frequency ,amplitude or phase or any combination thereof and finally comprising means to extract said viscous and dielectric information therefrom so as to yield the said qualitative or quantitative assessment of said material characteristic and/or its surface interactions therefrom and /or be used to quantify the amount/type of any sub-phase deposited therefrom upon the surface of the said sensor

<Desc/Clms Page number 9>

element. 11. A device as in claim 10 above wherein the oscillator output function F(O) has at least quadruple functionality with different weightings and power-law dependencies upon the material density

the material viscosity the material dielectric constant ,

and a surface factor, S.Fand wherein by manual or automatic adjustment of a voltage supply , the oscillator will become excited at various frequencies between Fs , that of series resonance and Fp , that of parallel resonance and at each successive frequency the relative weightings and power law dependencies of the quadruple dependent variables of F(O) vary in a unique material and surface dependent manner and thus material characterization and /or identification is possible based upon the calculated or observed functionality of this variation . 12 A method as in any of claims 1-9 above for the characterization of mixtures or impure organic solvents such as for example water adulteration of petrol , differentiation of DERV from gas oil and kerosene etc. 13. A device as in either of claims 10 or 11 above for the characterization of mixtures or impure organic solvents such as for example water adulteration of petrol ,

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differentiation of DERV from gas oil and kerosene etc . 14. A method as in any of claims 1-9 above for use with characterization of alcoholic liquor for instance, whiskey blend checking and differentiation. 15. A device as in either of claims 10 or 11 above for use with characterization of alcoholic liquor for instance , whiskey blend checking and differentiation 16 . A method as in any of claims 3-9 above wherein the surface of the piezoelectric element has been physically and /or chemically modified prior to material loading to facilitate investigation of effects of surface wetting and binding forces, 17 . A device as in claim 10 or 11 above wherein the surface of the piezoelectric element has been physically and /or chemically modified prior to material loading to facilitate investigation of effects of surface wetting and binding forces, 18 . A method as in claim 16 above wherein said modification is to encourage selective deposition of solid or liquid chemical sub-phases from the loading material. 19. A device as in claim 17 above wherein said modification is to encourage selective deposition of solid or liquid chemical sub-phases from the loading material. 5

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20 . A device as in any of claims 10,11 ,17 or 19 for use with drugs in the pharmaceutical industry. 21. A device as in any of claims 10,11 ,17 or 19 for use with isomers in the pharmaceutical industry. 22. A device as in any of claims 10,11,13,15, 17,19,20 or 21 wherein a cooling stage is employed in contact with or close to the sensor element to reduce evaporation of a volatile solvent when the same is the loading material or some part thereof . 23. A device as in any of claims 10,11,13,15, 17,19,20 or 21 wherein a heating stage is employed in contact with or close to the sensor element to increase evaporation of a non-volatile or low volatility material when the same is the loading material or some part thereof as for example with an oil . 24. A device as in claim 23 but for use with a beverage . 25. A device as in claim 24 but for use with an alcoholic beverage . 26. A device as in claim 25 but where the alcoholic beverage is whiskey. 27. A device as in claim 25 but where the alcoholic beverage is whisky. 28. A device as in claim 23 for use with motor oil. 29. A device as in claim 23 for use with DERV , gas oils and /or kerosene.

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Amendments to the claims have been filed as follows AMENDED CLAIMS 1. A visco-dielectric sensing method comprising the steps of firstly material loading a sensor element which has piezoelectric properties and secondly exciting the said element sequentially at both its series and parallel resonant frequency points so. as multiple frequency operation allows extraction of information concerning both the viscous and dielectric makeup of the said loading material, said extraxtion by monitoring of the circuit impedance at each said frequency point or by direct or radiative monitoring at each same said frequency point of the frequency ,amplitude and phase associated with the wave-form therefrom or any combination of the three aforesaid wave-form parameters thereof and in either case where the said material is either in a steady state thermal equilibrium with its surroundings or where it is in a temporal thermally induced or otherwise induced change of state , phase or flux and where the said information obtained allows for the qualitative or quantitative assessment of some characteristic of the physical and /or chemical makeup of the said loading material and/or its ability to interact with or flow upon ,leave by evaporation and/or deposit sub-phase material upon, the surface of the said sensor element ,governed by such factors as for example; volatility, surface tension , Van der Waals interactions, chemical binding or bonding, molecular weight and size density, viscosity, dielectric constant, surface roughness, evaporation dynamics , etc., further accordingly, the said loading material can cover all sides and parts of the said sensor element or alternatively only one side or part of the said sensor element is covered and in this second case dielectric coupling may be by fixed static capacitance of the piezoelectric material itself to the uncovered parts of the sensor element .

<Desc/Clms Page number 13>

2.A method as in claim 1 above wherein said sensor element is of the type which has traditionally been employed in quartz crystal microbalances . 3. A method as in claim 1 or 2 above wherein the said waveform is oscillatory. 4. A method as in claim 2 or 3 above wherein the said piezoelectric element is excited at some fixed operating points in between the series and parallel resonant points . 5. A Method as in claim 2 or 3 above except in that the said element is excited by being sequentially stepped or swept across the full frequency width between the series and parallel resonant points by means of a stepped or swept voltage supply. 6. A method in claim 2 or 3 and 5 above with voltage steps or sweep between two operating points over a significant part of the frequency width range between the series and parallel resonant points .

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7. A device to bring about the method of visco-dielectric sensing described in any of claims 1-6 above, comprising means to coat ,immerse or otherwise deposit the loading material or film or droplet thereof or sub-phase therefrom onto the said sensor element to bring about said loading further comprising means to bring about said sequential series and parallel excitation or said sequential or swept excitations at operating points in between by means of voltage steps or sweep and means to monitor the circuit impedance or directly or radiatively monitor the said wave-form frequency ,amplitude or phase or any combination thereof at each said operating point and finally comprising means to extract said viscous and dielectric information therefrom so as to yield the said qualitative or quantitative assessment of said material characteristic and/or its surface interactions therefrom and /or amount/type of any sub-phase deposited therefrom upon the surface of the said sensor element. 8. A device as in claim 7 above wherein the oscillator output function has at least quadruple functionality with different weightings and power-law dependencies upon the material density , the material viscosity ,the material dielectric constant , and a surface factor, .and wherein by manual or automatic adjustment of a voltage supply , the oscillator will become excited at various frequencies between Fs , that of series resonance and Fp , that of parallel resonance and where at each successive frequency the relative weightings and power law dependencies of the said dependent variables vary in a unique material and surface dependent manner and thus material characterization and /or identification is possible based upon the calculated or observed functionality of this variation .

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9. A device as in either of claims 7or 8 above for the characterization of mixtures or impure organic solvents such as for example water adulteration of petrol , differentiation of DERV from gas oil and kerosene etc .
10. A device as in either of claims 7 or 8 above for use with characterization of alcoholic liquor for instance, whiskey blend checking and differentiation
11 A device as in claim 7 or 8 above wherein the surface of the piezoelectric element has been physically and /or chemically modified prior to material loading to facilitate investigation of effects of surface wetting and binding forces,
12. A device as in claim l 1 above wherein said modification is to encourage selective deposition of solid or liquid chemical sub-phases from the loading material .
13 . A device as in any of claims 7,8 ,11 or 12 for use with drugs in the pharmaceutical industry.

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14. A device as in any of claims 7,8,11 or 12 for use with isomers in the pharmaceutical industry.
15. A device as in any of claims 7-14 wherein a cooling stage is employed in contact with or close to the sensor element to reduce evaporation of a volatile solvent when the same is the loading material or some part thereof.
16. A device as in any of claims 7-15 wherein a heating stage is employed in contact with or close to the sensor element to increase evaporation of a non-volatile or low volatility material when the same is the loading material or some part thereof as for example with an oil .
17. A device as in claim 16 but for use with a beverage.
18. A device as in claim 17 but for use with an alcoholic beverage .
19. A device as in claim 18 but where the alcoholic beverage is whiskey.
20. A device as in claim 18 but where the alcoholic beverage is whisky.
21. A device as in claim 16 for use with motor oil.
22. A device as in claim 16 for use with DERV , gas oils and /or kerosene 23 . A device as in claim 16 for use with water adulterated petrol .