Does EMF-responsive paint exist?
December 13, 2009 5:07 PM   Subscribe

I'm looking for a material I'm not sure exists. I want a plastic (or even better, a paint) that glows (at all) in response to being in an electromagnetic field.

Please tell me...does this exist? I'm willing to accept "exists but costs eleventy-billion dollars a microgram" answers as well. Thanks!
posted by swimming naked when the tide goes out to Science & Nature (22 answers total) 4 users marked this as a favorite
Well, photons (light) are carriers of the electromagnetic force. But not all photons are visible. You may be interested in .
posted by ecsh at 5:19 PM on December 13, 2009

bad html? fluorescence:
posted by ecsh at 5:19 PM on December 13, 2009

I'm gonna say, sadly, no. I have seen chalkboard paint and even magnetic paint, both available at my local big box. But this, not so much. In the fullness of time, yes.
posted by fixedgear at 5:26 PM on December 13, 2009

Depends what you mean by "field". In response to a non-contacting EM field, or in response to application of an electric current (still a field, but with 'contact')?

For the former: Google electrofluorescence / magnetfluorescence (hint: answers are likely to be in the "exists, but costs eleventy-billion dollars a microgram" category)

For the latter: EL tape / sheet
posted by Pinback at 5:36 PM on December 13, 2009

(on lack-of-edit window: magnetofluorescence.)
posted by Pinback at 5:38 PM on December 13, 2009

What type (wavelength) of electromagnetic field?

Like ecsh, objects that glow in the presence of an EMF of the type of UV light would be fluorescent objects. Just find some phosphorous, a good proportion of laundry detergents will work. There are probably also some substances that glow when bombarded with X-ray radiation. Glow-in-the-dark paints will probably also work. They glow in the presence of visible light, just not enough for us to really see it.

If you are looking for something that glows in the presence of radio waves or other short-wave radiation, it may not be as easy to find.
posted by that girl at 5:40 PM on December 13, 2009

What part of the EM spectrum are you interested in? It's an incredibly huge range! Are you interested in radio waves, or X-rays, or the EM field from power lines, or microwaves, or what?

There is no one material that is going to fluoresce across the entire spectrum--heck, there's no material that's even consistently transparent or opaque across the whole spectrum. So you're going to have to be more specific.

Blacklight (aka Dayglo) paint is perhaps the nearest thing, but I suspect you aren't even thinking about the part of the spectrum that it's reactive to (visible and ultraviolet).
posted by xil at 5:43 PM on December 13, 2009

In the fullness of time, yes.

Unless I'm mistaken, a paint, in the traditional sense, of being some kind of chemical slathered on something else, is not going ever do it, no matter how full or empty time may be.

Possibly something involving nanotechnology, where small particles could rotate in the presence of a magnetic field and change the color of the overall paint. That might do the trick. Similarly, some kind of substrate that is electrically powered could glow in the presence of an electromagnetic field, provided, I think, that there was a change in magnetic flux (gosh I hope I'm remembering my high school physics correctly).

As far as I know, there are pigments/paints that react in the presence of heat/cold, certain frequencies of light, and the presence or absence of electric current. But I don't think there are any chemicals that react in the presence of EMF.

Now, there is this newfangled stuff called paramagnetic paint. It technically changes color in the presence of an electric current, and furthermore you have to actually send that electric field through the paint. It also doesn't glow. But that might be the closest thing so far?

Totally unrelated item found during a google search: Electrical Current and Charges & Presence of the Holy Spirit. You can't make this stuff up.
posted by Deathalicious at 5:48 PM on December 13, 2009

If you're looking to coat something in this material, those little buggers that light up when your cellphone gets/makes a call are getting smaller and smaller and come in sticker form now.
posted by msittig at 6:00 PM on December 13, 2009

Ordinary fluorescent bulbs will glow under high voltage power lines.
posted by Rhomboid at 6:18 PM on December 13, 2009 [1 favorite]

If the EM field isn't changing constantly relative to the object, then no energy is transmitted and glowing in response is impossible. (If you figure out how to do it, you've invented perpetual motion.)

If the EM field is changing, then it might be possible, but the frequency (i.e. energy) of photons emitted will be a function of how much energy the changing EM field is applying to the object. And it turns out that visible light is very energetic. It takes a lot of energy to glow in frequencies that your eyes can see. Which means that the EM field would have to be very intense, and be oscillating at a very high frequency.

It would require a field that would put an MRI machine to shame. As strong as the MRI fields are, they only cause radio waves, which are several orders of magnitude less energetic than visible light. The field you need would probably be instantly lethal, assuming anyone could even figure out how to produce it.
posted by Chocolate Pickle at 7:03 PM on December 13, 2009

Thanks for all the answers. What I was hoping for was something like paint on household electrical wiring that would (even softly) glow when current was passing through the wire...without the "paint" being connected to a power source. Something about the same light amount as this. But, as CP says above, this amount of power may be considerably more than can be provided by the wiring's EMF. I wish it was otherwise, but c'est la vie.
posted by swimming naked when the tide goes out at 8:40 PM on December 13, 2009

Perhaps you could use a wire as an antenna to pick up energy from the wire by induction, connected to an LED (or something like the linked nightlight). Not paint, but it would be 'wireless' (or at least not directly plugged in). I'm not sure how much energy you can feasibly pick up that way though.
posted by alexei at 9:04 PM on December 13, 2009

For 23 bucks at Amazon you can get a non-contact voltage tester: It "senses the steady state electrostatic field produced by ac voltage through insulation without requiring contact to the bare conductor." I've never had an excuse to buy one, but I think it might not do what you want, because (I think) it senses a "hot" AC wire even if there's no current being drawn.
posted by Dave 9 at 10:32 PM on December 13, 2009

Some interesting stuff here too. Someone suggests that you might be able to use a compass.
posted by Dave 9 at 11:03 PM on December 13, 2009

The non-contact liveness testers are capacitively coupled and they depend on being held by a person (big charge reservoir). They do draw a minute amount of current despite the lack of contact, due to the capacitive effect. Doesn't work with DC.

I'm very intrigued by msittig's answer. What are these things of which you speak?
posted by polyglot at 11:17 PM on December 13, 2009

If you mean one of these, they contain a non-trivial amount of circuitry to receive radiation in the right band and power up an LED.

This on the other hand, I dunno (talk about a content-free article!). Probably the same, but with better-hidden electronics.
posted by polyglot at 11:22 PM on December 13, 2009

Yeah, every teenage girl in Tokyo has five of those hanging from her phone.
posted by rokusan at 1:06 AM on December 14, 2009

If you just want to indicate the presence of current in the wire, perhaps you could use slightly thinner-than-normal wiring and some heat-sensitive paint? If you don't mind a fire hazard, that is. (And a slow response time.)
posted by caaaaaam at 1:36 AM on December 14, 2009

From, of all places, the Wikipedia page for "paint", emphasis mine.
Electrochromic paints change color in response to an applied electric current. Car manufacturer Nissan has been reportedly working on an electrochromic paint for use in its vehicles, based on particles of paramagnetic iron oxide. When subjected to an electromagnetic field the paramagnetic particles change spacing, modifying their color and reflective properties. The electromagnetic field would be formed using the conductive metal of the car body.[4] Electrochromic paints can be applied to plastic substrates as well, using a different coating chemistry. The technology involves using special dyes that change conformation when an electric current is applied across the film itself. Recently, this new technology has been used to achieve glare protection at the touch of a button in passenger airplane windows.
Subsequent searches online for "electrochromic paint" yields all sorts of nifty info.

So while applicability to your own purposes is pretty unlikely, and this is a very strong field we're talking about here (not ambient EM), I think the technical answer to your question is "Yes, this exists."
posted by rokusan at 2:30 AM on December 14, 2009

I don't know about paint, but you can buy small sheets of film that respond visually to magnetic fields.

I have one, it's not the most dramatic thing, but it does a decent job of showing the profile of a magnetic field.

You could also do iron filings suspended in a liquid, sitting next to the wire.

I like alexei's idea very much. If you had an LED with a coil that could pick up the field and light the LED, you could move it around the wire and create a visualization of the field by taking a very long-exposure picture of the LED as it moves, just like this phenomenal visualization of the shape of RFID fields.
posted by fake at 3:23 AM on December 14, 2009

AC wiring has two opposed magnetic fields that cancel each other out. It decreases the amount of flux you are going to have to detect.

That is why when you want to use a non-contact current meter, you have to split the power cord in half and put the sensor around ONE of the leads. It doesn't matter which one. By definition, (unless there's a ground fault), the current out has to equal the current in.

Super-conductive quantum interference devices (SQUIDs) are highly sensitive magnetic flux sensors, capable of seeing magnetic flux from your brain, but you have to cool them to near absolute zero.

Problem #1 in visualizing any unseen force is gaining access to it or its associated analogue.

I don't see doing this passively or parasitically, which is what you are apparently looking for. I see MANY ways of doing it with additional parts.
posted by FauxScot at 5:15 AM on December 14, 2009

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