Chemistry: molecular biology and microbiology – Apparatus – Including measuring or testing
Patent
1992-04-22
1994-03-22
Wityshyn, Michael G.
Chemistry: molecular biology and microbiology
Apparatus
Including measuring or testing
435291, 422 8205, 422 8212, 374 31, 374117, C12M 140, C12M 134
Patent
active
052963748
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an apparatus for assessing a property of a medium, particularly but not exclusively a fluid medium.
BACKGROUND OF THE INVENTION
A known form of apparatus for assessing a property of a fluid comprises an optical fiber coated near its tip with an enzyme or antibody. When the coated tip is contacted with the fluid, enzyme-catalyzed reactions create localized heating and expansion of the fiber and the rate of expansion, ana hence the rate of reaction, is measured by comparing the fiber length with that of an adjacent reference fiber using interferometry. The known apparatus is not temperature stable and operation depends on the expansion of an optical fiber which is a disadvantage where space is limited.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new and improved form of apparatus for assessing a property of a medium in which the aforementioned disadvantages are obviated or substantially mitigated. This is achieved by using an apparatus wherein localized heating, created for example by a chemical reaction, causes the resonant frequency of a vibrating member to change, the change in frequency being an assessment or measure of the property.
According to the present invention there is an apparatus for assessing a particular property of a medium, comprising at least one vibratile element located within a closed chamber and mounted on a structure part of which structure forms said chamber, means for delivering excitation energy to said vibratile element to cause the element to vibrate at its resonant frequency, means for monitoring and detecting the vibration frequency of the vibratile element, and sensor means mounted on an exterior surface of the chamber structure to enable contact with the medium, the sensor means being thermally activated when contacted with a medium having the particular property whereby to change the temperature of the chamber and hence the resonant frequency of the vibratile element, which change as monitored and detected by the monitoring and detecting means provides an assessment o the presence of the particular property of the medium.
The property of the medium may be temperature, biomass, pH or dissolved gas content. Alternatively the property may be the presence in the medium of a natural or synthesized chemical or biological species e.g. an antibody, an antigen, or a barbiturate capable of being conjugated with a sensor means which includes an enzyme.
The energy is preferably light but may alternatively be electrical or ultrasound.
The vibratile element may be fabricated from a semi-conductor wafer and when optical excitation is used may be disposed relative to an optical fiber delivery means to form a Fabry-Perot cavity so that the element is self-oscillating when the energy is continuous or the element may be maintained in resonant oscillation, (without forming a cavity with the delivery means by a feedback drive system applied to the delivery means.
Furthermore, when the delivery means delivers electrical energy a pattern of conductive electrodes having tracks linking the delivery means and collecting means may overlie the vibratile element and be so arranged as to stimulate the vibratile element into resonant oscillation and detect the oscillations using electrostatic and/or electromagnetic forces. Where this arrangement is used the vibratile element is made of conductive material and may or may not be current carrying.
The substrate of the structure may be N type locally N.sup.+ doped and contact may be made by virtue of a metallization applied to the N.sup.+ contact diffusion which in turn may be positively charged. A further metallization which is negatively charged may be in contact with a P.sup.+ doped layer of which the vibratile element forms part. The metallization may be connected to a voltage source through a silica post having disposed on its surface metal tracks which at the supply end are in contact with the voltage source and at the other end are connected to said N+ and P+ lay
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Mosbach et al. "Thermal bioanalyzers in flow streams enzyme thermistor devices" Analytical Chem., vol. 53, No. 1 (Jan. 1981) pp. 83;84;86;89-91, 94.
Xie et al. "A versatile thermal biosensor" Sensors and Actuators, vol. 19, No. 1 (Aug. 1989) pp. 53-59.
Culshaw Brian
Turner Anthony P. F.
Beisner William H.
University of Strathclyde
Wityshyn Michael G.
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