What is a chemical sensor?

Fundamentals
The chemical properties of a substance can be detected and measured with chemical sensors (Getty Images)

A chemical sensor is a device that measures and detects chemical qualities in an analyte (the scientific term for a chemical substance being observed) and converts the sensed chemical data into electronic data. Chemical sensors are used in myriad applications, such as medical, automotive, nanotechnology and home detection systems (i.e. carbon monoxide detectors).  

There are many different types of chemical sensors—which are specifically designed for their intended functions)—but they all share two components: receptors and transducers. The receptor is the component of the chemical sensor that comes into physical contact with the analyte. Depending on the sensor, the receptor interacts with the analyte in distinct ways. For instance, some receptors trigger chemical reactions with the analyte as a whole, while others can single out specific molecules. The latter (sensors that target molecules in an analyte) are referred to as more “selective.”  

Chemical Sensor Diagram
Chemical Sensor Diagram (ResearchGate)

The second component held in common with all chemical sensors is the transducer. Transducers are responsible for intaking the chemical information of the interaction between the receptor and analyte and converting it into corresponding electrical information. This information is then sent to a computer or a mechanical component. The transducer may increase or decrease resistance, trigger an audible alarm, or present the data on a screen (interface). 

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A perfect example of a commonly used chemical sensor in action is a breathalyzer. When people consume alcohol, they exhale an amount of alcohol molecules directly proportional to the amount they drink. A breathalyzer is a chemical sensor that is specifically designed to measure a person's blood alcohol content (BAC), often to determine whether or not they are safely capable of driving a vehicle. When the alcohol molecules interact with the receptor, they encounter another chemical substance contained in the receptor (namely: sulfuric acid, potassium dichromate, silver nitrate and water). This triggers a chemical reaction, and when the chemical difference between the two chambers (one not affected by the reaction) is perceived, an electric signal is produced and it indicates via screen or needle the suspect’s BAC.

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