A device for detecting an analyte in a sample, which includes a radiation source adapted to generate electromagnetic radiation; a transducer capable of transducing a change in energy to an electrical signal; at least one tethered reagent on or proximal to the transducer, the tethered reagent having a binding site which is capable of binding the analyte; a chamber for holding the sample in fluid contact with transducer, wherein the chamber is adapted to contain the sample on inversion, partial inversion or agitation of the device; and a detector which is capable of detecting the electrical signal generated by the transducer.