Method for sensing a chemical

1. A method for detecting an analyte in a sample, comprising the steps of:

providing a transducer having a pyroelectric or piezoelectric element and electrodes which is capable of transducing a change in energy to an electrical signal, a first reagent immobilised on the transducer, the first reagent having a binding site which is capable of binding the analyte or a derivative of the analyte,

exposing the sample to the transducer thereby allowing the analyte or a derivative of the analyte to bind to the first reagent to form a first reagent-analyte complex immobilised on the transducer, the binding creating a new reagent-analyte binding region on the first reagent-analyte complex;

introducing a second reagent, which does not bind to the first reagent in isolation and does not bind to the analyte in isolation, wherein the second reagent has a label attached thereto which is capable of absorbing the electromagnetic radiation generated by a radiation source to generate energy by non-radiative decay, the second reagent having a binding site which is capable of selectively binding to the new reagent-analyte binding region created on the first reagent-analyte complex, and thereby immobilising the second reagent and label on the transducer;

irradiating the sample with electromagnetic radiation;

transducing the energy generated by the label into an electrical signal;

detecting the electrical signal; and

using a time delay between the irradiation of the sample and the generation of the electrical signal to determine the presence of label immobilised on the transducer to thereby indicate the presence of analyte in the sample.

2. A method as claimed in claim 1 , wherein the first and second reagents are antibodies.

3. A method as claimed in claim 1 , wherein the label is selected from a carbon particle, a coloured-polymer particle, a dye molecule, an enzyme, a fluorescent molecule, a metal particle, a haemoglobin molecule, a magnetic particle, a nanoparticle having a non-conducting core material and at least one metal shell layer, a red blood cell, and combinations thereof.

4. A method as claimed in claim 1 , wherein the first reagent is adsorbed on to the transducer.

5. A method as claimed in claim 1 , wherein the transducer is located in a sample chamber.

6. A method as claimed in claim 5 , wherein the chamber is a well.

7. A method as claimed in claim 5 , wherein the transducer is integral with the chamber.

8. A method as claimed in claim 1 , wherein the sample contains suspended particles.

9. A method as claimed in claim 1 , wherein the sample is whole blood.

10. A method as claimed in claim 1 , wherein irradiating the sample comprises generating, by the radiation source, a series of pulses of electromagnetic radiation, and detecting the electrical signal comprises detecting, by a detector, only the electrical signal generated by the transducer up to a selected time delay between each pulse of electromagnetic radiation from the radiation source and the generation of the electrical signal.

11. A method as claimed in claim 1 , wherein the method is carried out without removing the sample from the transducer between the steps of exposing the sample to the transducer and irradiating the sample.

12. A kit comprising:

(i) a device for detecting an analyte in a sample comprising a transducer having a pyroelectric or piezoelectric element and electrodes which is capable of transducing a change in energy to an electrical signal, a first reagent immobilised on the transducer, the first reagent having a binding site which is capable of binding the analyte or a derivative of the analyte to form a first reagent-analyte complex immobilised on the transducer, the binding creating a new reagent-analyte binding region on the first reagent-analyte complex, a source of electromagnetic radiation, and a detector for detecting the electrical signal; and

(ii) a second reagent, which does not bind to the first reagent in isolation and does not bind to the analyte in isolation, wherein the second reagent has a label attached thereto which is capable of absorbing the electromagnetic radiation to generate energy by non-radiative decay, the second reagent having a binding site which is capable of selectively binding to the reagent-analyte binding region created on the first reagent-analyte complex formed between the first reagent and the analyte or the derivative of the analyte and thereby immobilising the second reagent and label on the transducer.

13. A kit as claimed in claim 12 , wherein the first and second reagents are antibodies.

14. A kit as claimed in claim 13 , wherein the label is selected from a carbon particle, a coloured-polymer particle, a dye molecule, an enzyme, a fluorescent molecule, a gold particle, a haemoglobin molecule, a magnetic particle, a nanoparticle having a non-conducting core material and at least one metal shell layer, a red blood cell, and combinations thereof.

15. A kit as claimed in claim 13 , wherein the first reagent is adsorbed on to the transducer.

16. A kit as claimed in claim 13 , wherein the device further comprises a sample chamber and the transducer is located in the sample chamber.

17. A kit as claimed in claim 16 , wherein the chamber is a well.

18. A kit as claimed in claim 16 , wherein the transducer is integral with the chamber.

19. A kit as claimed in claim 13 , further comprising a controller configured to control the radiation source to generate a series of pulses of electromagnetic radiation, and wherein the detector is configured to detect only the electrical signal generated by the transducer up to a selected time delay between each pulse of electromagnetic radiation from the radiation source and the generation of the electrical signal.