Optode

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.

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.

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.

An optode is capable of measuring many substances and reactions, but the most common measurement is light-based.