objects that react physically to light?

nlaham

Does anyone know or have heard of any object that will react or change physically to light (and not necessarily because of temperature)?

I know materials expand and contract with temperature, but do any materials or objects change their physical form by light or radiation alone? I thought photovoltaic cells, or even pigment in ones skin, but that seems more of a chemical reaction than a physical one.

Sunflowers?? Haha just kidding, but for real. Anything out there today of this nature.

gb7nash

Any plant that makes use of photosynthesis:

http://en.wikipedia.org/wiki/Photosynthesis

nlaham

Anything non-biological?

gb7nash

Well.... there's always the hexbug.

http://www.insectkits.com/contents/en-us/d59_crab.html

As far as something not manmade and not biological, I can't think of anything.

nlaham

haha! I might have to buy one of those.

Although the hexbug is powered by solar cells, which is a chemical reaction right? Either way, nothing actually moves in the PV cells (except the electrons I suppose)

vinniewryan

There are UV curable materials, but they would only get harder with more light introduced (until fully cured).

Andy Resnick

I think you are splitting hairs- a substance can only 'react' to light if it absorbs the energy. The electromagnetic energy can be converted into a number of other forms: heat, chemical, electrical, etc.

http://en.wikipedia.org/wiki/Photochromism
http://en.wikipedia.org/wiki/Vitamin_A
Vampires

gb7nash

Best answer yet.

Lsos

Light hitting an object puts a pressure on that object. It's a very small pressure, but it's there. So you can say that all objects will accelerate or strain when having a light shone on them.

nlaham

HAH! I said non-biological.

Lsos, you don't happen to know any simplified equations off hand that relate the pressure or acceleration to radiation? Not that I could really use them for practical purposes but now I am just more curious then anything.

SpectraCat

On the molecular level, there are many molecules that undergo conformational changes (i.e. changes in their shapes) when they absorb light of a particular frequency ... actually the mechanism of vision works this way. The retinal moeity of the rhodopsin protein absorbs a photon and changes it's conformation, which is the initiation step of the signalling cascade that lets your brain know a vision receptor was stimulated.

These types of molecules are sometimes incorporated into nanotechnology designs as light-activated sensors/switches, but I am not aware of any macroscopic systems that behave in this way, and meet the criteria you have established.

DaveC426913

LOTS of materials break down in the long-term presence of light. Textiles, plastics and dyes readily come to mind.

Usually, it's the UV light that does the most damage.

Oxygen gas breaks down into monatomic oxygen. Lots of chemical reactions in the atmo around ozone that happen in the presence of light...

pallidin

My clear vote is for Nitinol.(memory metal)
Though shinny, if coated black and hit with sufficient light, especially IR, a dramatic physical transformation takes place.

SpectraCat

Isn't that a heating effect though? I though the OP wanted to rule those out ... although as Andy Resnick pointed out, this is largely a semantic difference for macroscopic samples of molecules.

pallidin

Yes indeed. But doesn't IR qualify as a photon-enabled trigger of physical transformation in this case?
Perhaps that's not what OP intended though, as you say.