Question: what do crystals do as a job within the sensor?

Lynne Thomas answered on 20 Jun 2014:

Crystals are special things as they are a regular arrangement of atoms and molecules into a grid much like a three dimensional brick wall. Most solids are crystals so very cheap common things like salt and sugar through to expensive gems like diamonds, but also things like your mobile phone battery, the hard drive in your computer, the metal that makes your car or the drug molecules you take to relieve a headache like paracetamol or aspirin. The timing device in watches is a single crystal of quartz and its vibrates very regularly when you apply a voltage across it making it reliable as a time-keeper.

It is a combination of both the type and number of atoms and molecules in the crystal and also the arrangement of them that gives a material it’s properties. Think about diamond and graphite for example. Both are made of carbon, just carbon on its own but diamond is very hard and colourless whereas graphite is soft and grey. In diamond the carbon atoms are connected strongly in three-dimensions but in graphite they are only strongly connected in two-dimensions.

I’m making materials which change colour when you heat them or squeeze them so they could act as temperature or pressure sensors. The way that they do this is not just a matter of what molecules I have made, but also how they are arranged in the crystal. So the sensors wouldn’t work if they weren’t crystals!