is there a such material

that is almost gel like

that is light sensitive and will contract and retract depending how much light goes through it?

sorry if this is a stupid question i don't no much about science

There are heat sensitive materials.. Which is similar to visible light

pretty much this, what is it for? if an electrical detector is an option, they have an extremely inexpensive furnace component called a "CAD cell". i have no idea what to go with for a "gel" system.

An eyeball. I have two of them.

Winner

That's a collection of tissues, not really a material. The muscles that contract aren't a gel.