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I love LED's and am always looking to use them in new ways. Especially for cool effects. I found a great way to couple a blue LED into 1/4 inch tubing. Then by filling the tubing with fluorescent liquid, a glow tube can be created. It took a little experimentation to get right and ended up being very simple. Here is what you will need:

1. Quarter inch clear Tygon tubing (Lowe's or Home depot carries it)
2. Ultra bright blue LEDs (5mm, clear lens, narrow beam i.e. 12-15 degrees)
3. A small plastic squirt bottle similar to a condiment dispensing bottle 
4. a Fluorescent Highlighter (Available at most office supply stores)

Step 1: Preparing the Florescent Dye

The first step is to prepare the dye. Take the back off of the fluorescent highlighter. You can ether pry the ink reservoir out. It is an absorbent cylinder soaked in the dye. My first try at this I pulled it out and used a lot of the dye. I put about a teaspoon into the plastic squeeze bottle. This was way to much. It causes the light to be used quickly and not travel far down the tubing.

What ended up working best and is easiest it to place the end of the highlighter over the mouth of the squeeze bottle and let the water absorb some of the die

Step 2: Filling the Tubing

The key to t his is to fill the tubing with no air bubbles and then to seal it by pressing in the 5mm LED. They fit perfectly into the tubing and act like corks. They are actually quite hard to remove if  you realize you have air bubble later. 

1. Have your LED's standing by so you can grab one quickly
2. Hold the tubing so that the ends are even
3. Hold the nozzle of the squeeze bottle next to one end of the tubing
4. Squeeze the bottle so as to have the liquid flow out the other end of the tubing
5. Pull the bottle away and stop squeezing. If you stop squeezing first, the bottle sucks liquid back out of the tube.
6. Push an LED into one end of the tube to seal it.

Step 3: Sealing the Tubing

Now we have to get the next LED into the tubing without air bubbles. Do this by dripping a few extra drops of liquid into the open end until it is completely full. Now press the second LED into the tube to seal it.

Step 4: Testing

For testing purposes I used a CR2032 battery just like an LED "Throwie" uses. It is perfect to test and depending on your final use can power the LED Glow tube for costumes etc. You can get these pretty cheap from Dealextreme: http://www.dealextreme.com/details.dx/sku.751

Step 5: Use and Final Thoughts

These are not quite as bright as a glow stick in the first few minutes. They are brighter than the glow necklaces that are sold at a lot of events. What is really cool is that  you get the green glow and some blue leaks through also. The glow definitely drops off further away form the LED but by lighting both ends it makes up for it. The other cool thing for me is that it looks different than EL wires and chemical glow sticks. Begging the question of just what is it? 

Interestingly, I started out with UV leds and found that they do work but are not as effective at florescence es as the the blue LED's. Mine are 470nm and my UV ones were 405um. Also the minimal amount of die needed was a surprise.  I tried an orange and pink fluorescent highlighters too but they were no where near as bright.

I am wiring mine up with 330Ohm resistors so I can power them from 12 volts for a couple Halloween projects. They can be directly connected to the little CR2032 batteries and will last for a couple days, although at reduced brightness. 

What projects can you put these into?

Jules
are these normal led or gree led?
They are blue LED's. I also tried UV but the blue worked better <br> <br>Jules
Wow, seems like there's a lot of debate online in general about the best combination of light source and fluid for different colours and maximum illumination. I've noticed it seems to be common to finely sand the tubing in order to frost it and further diffuse the light so I'm going to give that a try as well.<br/><br/>For those considering different colour options with UV-sensitive liquids, this page has a decent list of substances with different colour results under UV:<br/><br/>http://chemistry.about.com/cs/howthingswork/f/blblacklight.htm
Thanks for that link. I need to update this with some more info. I bought one of those commercial water safety dye markers that is pure florescene. Want to try mineral oil too. It would be good to find a suspension particle for the liquid that would alleviate the need to sand the inside of the tubing.<br><br>Jules
<p>I have heard that titanium dioxide can work well to diffuse the light, have you come across this? Also I am thinking of using a similar project inside a piece of copper piping with various holes and grooves in it, do you think this would work or would the copper just absorb the light?</p>
<p>If the copper tubing is straight, I would use some frosted tubing inside it and a really bright LED. The titanium dioxide will diffuse the light but not really fluoresce. Give it a try and post some pics!</p><p>Jules</p>
Will do thanks for the advice
<p>I was actually going to make some just like these... before ever seeing this instructable. I was just looking for how to secure the LED.</p>
That is the beauty of this project. The LED's press fit into the tubing, sealing the liquid inside.<br><br>Jules
<p>Do you have anything that might hold it in better? It needs to be able to take some motion.</p>
<p>Honestly, I thought UV should do even better, but if you say it's not, I'm rethinking a project of mine that I'm doing. Anyhow, I believe, if you put more dense liquid (more marker juice), that UV should do the best, especially if you want to hide the light source, but the pipe would have to stay straight. Now I have that fluid in a glass bottle for quite a long now, 4-5 years or so, and it never changed, so the main problem I see in things like these is that it has to be evenly lit at all times. Unless, if you perhaps could make the tube reflect it more, which is kinda impossible, due to the fact that you have to see through it, but definitely oils come in mind as an option, also testing different densities of the juice.</p>
Yea, I have wanted to try mineral oil or something. Just never got around to it. But... Halloween is right around the corner. Might have to bust out some LED's...<br><br>Jules
<p>I have a 5 gallon bucket of white mineral oil. If I could use it for this effectivly that would be awesome.</p>
<p>Definitely try it, all in all this is great! I'm working on a pretty big prop with lots of details, and am trying out different diffusers. Right now, all this glowing liquid parts, have to be in glass or plastic containers, that are not so elastic, so I could keep them straight and lit evenly. They probably won't be full of liquid, so it looks as an exotic fuel of some sort (that it's obvious as a liquid). On the other hand, if it's only about the glow effect, I'd go with acrylic rods, sanded down (set aside that I can't find any in my area), also, as a diffuser plexiglass, and different white/milky rubbers and acrylics :)</p>
<p>Can i use water instead the fluorescent thing... Will it still glow?</p>
If the water is &quot;cloudy&quot; you will get light. With out the fluorescing agent, it wont really glow, it will light up. <br><br>Jules
<p>Why is it important to use a fluorescent dye? Isn't that simply changing the colour of the light? What if the tube contains just water/oil and no dye?</p><p>I noticed you talked about using mineral oil, presumably because of its high refractive index. If fluorescein (available in powdered form on eBay) does not dissolve in oil maybe you'd have more success with glycerol which I think is somewhat polar and also has a high refractive index.</p>
The fluorescent die is doing more than changing color. It is emitting light in all directions. Without that or diffuser in the liquid, the tube ends up acting more like a light pipe. IT carries the light from one end to the other without emitting it out of the tubing so it &quot;glows&quot;. It has been a while but I need to revisit this project and maybe do an update.<br><br>Thanks,<br><br>Jules
<p>I was hoping to make something with RGB LEDs that would be colour-customisable. Is this unachievable due to the need for a dye?</p>
<p>Give it a shot, might work!</p>
I have 3w n 10w uv leds, might try this out
Cool. Post pictures if you do.<br><br>Jules
Sweet,,gives me plenty of ideas, thanks
I saw an instructable for an infinity of mirrors with a light tunnel. I can see this being applied to give a more solid tunnel of light. ELs would work too without the risk of leakage/mold. <br>https://www.instructables.com/id/cool-DIY-infinite-LED-tunnel/
<p>Kinda new here, if you have a link, please if you'd share, I'd be grateful!</p>
cool much cheaper than el wire.. <br>
Thank you!
Great idea,congrat! <br> I need something smilar now for one m new projects. Question is how long that fluid is fluorescent? The chemical rods are just for short time, the EL wires for a few months maybe...What do you think about this? <br>Thanks
THe fluid remains fluroescent a long time. THe problem I have seen is the tube dries up after a year or so. What I need to try (And it is on my to do list) is dissolving the fluoresene in mineral oil or the like. <br><br>Jules
...that already exists. I once bought a canister of that stuff on ebay. The vendor said, it's generally used by Airbus to find tiny cracks in airplane wings. I used it as paint, but it's volatile and nearly gone after a month or so. <br>You can also buy Fluorescein as a dry powder. And check out this instructable; might come in handy, if you want to make sumthin bright, i guess: https://www.instructables.com/id/Building-a-Lightsaber/
Hey Jules, <br>Is there anyway i can get in contact with you? <br>Im looking at using this idea in a product im making and would be intrested in any new developments or better solutions to use in the tubes for my product <br>Thanks Elliott, Chaspudz@gmail.com
Great instructable! I love these. I was looking for something like that. I will make this so they flash to my music then wire a bunch of them around my room. Thanks again for this great ible.
You are welcome!
i love this idea. i used this concept in something i made, thanks for the inspiration. i posted it if you want to take a look. <br> <br> have fun
Thanks! I just got a couple ten watt Blue LED emitters that I am hoping to have time to get to for this one on steroids. Check it out here: http://www.dealextreme.com/p/10w-180lm-445-447nm-blue-light-led-emitter-9-11v-100875<br><br>Jules
Is there a better way of securing the batteries so they can be added and removed easier? I would be looking to swing these about for light painting but would be worried the battery would fly out as well.
If you solder wires to the LED, you can run them back to a battery in your pocket and only sing the tubing part. Also if you use a nine volt battery, you need to add a 200-300 ohm resistor in series.<br><br>Have fun!<br><br>Jules
Oops. I didn't read the next page yet.
Couldn't you use UV Leds?
ok ill be hounest im lighting up my deadmau5 helmet and i cant figure out the resistor i need to wire 12 white leds too what even portable power sorce i need i need help i have a on off switch 12 white leds and the toobing <br>
If you are using a white led each one drops about 3.5 volts and you want about 20ma to each so you need a resistor that would be (your supply voltage -3.5) divided by .020 amps. In a nut shell 200-330 ohms for 10-12 volts and about 75-100 ohms for 5-6 volts.<br><br>Post a pic when you are finished!<br><br>Jules
soo what battery should i use
so for the blue color you used what?
Come to think of it, couldn't you use use EL Wire to illuminate the water? It would be so much brighter!
If your using UV led's, have you considered using tide detergent? I work on a tech crew and we have these 18&quot; UV cannons that we shine at a wall which we painted with tide. the effects are pretty sweet. The only problems i forsee is coming up with a diluted solution that doesnt creat suds...
who can send me The PDF Format of this Project please
How long it the tube in the last and second to last pic on step 5????????
how long is the biggest one?
about 18&quot; but the glow isn't even across the tube, it falls off away from the LED<br><br>Jules
so how long can the tube be without the glow dimming?

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Bio: I started taking things apart when I was 6 started putting them back together at 8 and they actually worked again when I was 10 ... More »
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