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What Is an Optode?

Alex Newth
Alex Newth

An optode is an optical sensing device capable of measuring many aspects of a substance — commonly airborne or submerged — if a user points the device at the substance. Three parts are required to make an optode work; one is a polymer that captures the substance to be measured. A chemical or energy signal is applied to the captured substance to cause a reaction, based on what is being measured. After the reaction occurs, electronic components calculate the reaction and make a numerical or colorful representation. The optode is capable of measuring many values, such as phosphorescence, absorption and oxygen, and most measurements involve light.

For a reaction to occur, the optode must first capture a substance. This can be done by pointing the device at a substance, but this is unreliable. Without something to keep the substance captured, it can escape the device, leading to inaccurate readings. Instead, a polymer is used that bonds with the substance and forces it to remain in the device. When measurements are calculated, the polymer does not affect the reaction.

Woman holding a disc
Woman holding a disc

After the substance is captured, another substance must be exposed to it to cause a reaction. This second substance is determined by what the optode measures and what the captured substance is. Some optodes may skip a reacting substance in favor of using an energy or light source that will cause a reaction based on the amount of energy, though these units are uncommon.

Once the reaction occurs, it must be represented to the user so he or she understands the measurement. This is performed by the electrical components inside the optode. By collecting information from the reaction, the electronics create either a colorful or numerical representation. For example, the device may emit red light to show a reaction has high phosphorescence. Numerical representations are more precise, but this pushes up the device’s cost and may not be practical, depending on what is being measured.

An optode is capable of measuring many substances and reactions, but the most common measurement is light-based. For example, if someone needs to know how much light a substance absorbs or repels, then this device can measure the exact amount. Another common use for this device is to check the amount of oxygen in water, based on its concentration and saturation. For easy data retrieval, most optode units can be connected to a computer, which instantly receives the measurements and readings.

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