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How Chemical Sensing Devices Work

        Science | Devices

How Chemical Sensors Help

No matter how they operate, chemical sensing devices are, without a doubt, working for you. Your home probably has at least a one detector for radon gas, smoke or carbon monoxide, depending on the laws in your state or country. Many radon sensors work by absorbing the radon itself or detecting the radioactive decay products of the lethal gas. Carbon monoxide, on the other hand, is not a radioactive material, so the detectors for this gas operate differently. One of the most common mechanisms for this chemical sensor is a riff on biology. These detectors mimic how carbon monoxide interacts with hemoglobin in blood in order to determine the presence of the gas. Another common detector in the home is a smoke detector. While some use radioactive materials to help sniff out smoke, most of the sensing in smoke detectors comes from the physical, not chemical, phenomenon of the smoke particles causing interference that is sensed by the detector.

Chemical sensing devices also have widespread use outside the home. One of the main places you'll see these devices in action is in search of biomolecules in medical settings. Biomolecule sensors are essentially specialized chemical sensors. Although they detect substances like hormones, these bodily substances are all molecules. After all, these sensors are made with many of the same guiding principles as other chemical sensors – selectivity, sensitivity and portability.

Some of the most portable biomolecule sensors you may be aware of are associated with fertility measurements: pregnancy tests and ovulation tests. Both these chemical sensors detect the presence of certain hormones in urine. In the case of pregnancy tests, the sensor looks for the hormone human chorionic gonadotropin (hCG) in urine. The stick on which the woman urinates has antibodies that are coated with a chemical that bonds to hCG. If the biomolecule is present, the test reads positive [source: Parents Magazine]. Usually these chemical sensors have a colorimetric component so that when the analyte – in this case hCG – binds, it triggers a color change in the sensor, making the readout of the results pretty foolproof.

In the clinical setting, two of the most common methods for chemical-based biomolecule detection are ELISA (enzyme-linked immunoabsorbent assay) and the Western blot. Depending on the size and type of the biomolecule in question and the information they want about the molecule, scientists and clinicians will often turn to one of these chemical sensing techniques to identify different analytes in mixtures of biomolecules [sources: ThermoFisher Scientific, Mahmood and Yang].

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