March 14, 2011

toothpaste diode

One day I was reading the back of a toothpaste tube and realized that the secant ingredient was Hydrated silica which is nothing more then silicon oxide mixed with water. So I started to wounder if I making a from it transistor would be a possibility. I thought it might be easier to start with something simpler. So I decided I'd make a diode. The detailed of why this worked is after the photos. If you just want to see the photos and don't care about the chemical proses involved then all you need to know is I smeared toothpaste on a peace of chrome and lit it on fire with a propane torch. After testing I found that I had to add a 10 k resistor in series with the diode because the breakdown voltage was so low that my multimeter  was braking it down. The diode layer is thin and can be scratched off easily resulting in a fun hunt for a new diode spot. I did this once and it took half an hour to find another spot that worked as well as the first one. This diode is probably only useful for crystal radios as anything else would have to much voltage. 

Its showing 0 conductivity the line on the meeter
just extends past that point. 

Here you can see the 10 k ohm reading from the resistor the
 diode itself had almost no readable resistance. 
My toothpaste contained  13 ingredients:
Water, Hydrated Silica, Glycerin, sorbital, PVM,MA copolymer,
 flavor, sodium lauryl sulfate, cellulose gum, sodium hydroxide,
 propylene glycol, carrageenan, sodium saccharin, dye, and fluoride. 
If I lit this on fire then most of it would burn off leaving me with mostly silica and sodium covered in ash.

So it was pointed out that when bonded sodium looses its outer electron and thus will become a p-type semiconductor. So this explanation is now all BS. Anybody know whats making th n-type semiconductor?

Hear's the scientific bit that makes it work:
Sodium is negatively charged so if I debond it with heat it will stick in the Silicon giving me an n-type semiconductor. Witch is half of a diode. I'm not positive but I now think that it is the Sodium Iauryl Sulfate steeling electrons from the shakedown of other chemicals and becoming negatively charged that is forming the n-type semiconductor. To form the other half I needed a P-type semiconductor so I looked around my desk and found a peace of chrome.(the chrome might not be necessary as the Sodium might make the P-type semiconductor) Chrome is positivity charged so if I got some of it to mix with the Silicon then I would get my P-type semiconductor.  Luckily for me the toothpaste contained Sodium Hydroxide AKA Lye. Lye reacts with chrome and is often used as a dechromeing agent. As it oxidizes the chrome it creates heat witch burns off the lye. Now there is a thin layer of chrome doped silicon under a layer of sodium doped silicon all rapped up under a layer of soot  which can easily be cleaned off. After cleaning you are left with a peace of metal with a thin layer of silicon on it with spots that work as a diode, spots that are non conductive, and spots that are always conductive. 

Note: I'm not a chemist nor do I necessarily know what i'm talking about if you know I'm wrong let me know and I'll consider revising this. 


  1. Can you do a diagram of forward voltage versus forward current? What is the maximum forward current for this type of diode?

    When will your diode go into production and can you deliver quantities >1000?

  2. . I agree a toothpaste diode is not a hack, but it is a build, and very notable one. This is innovative.

  3. It changes the experience completely!! I agree that red, sparkly toothpaste is definitely just freakin' weird.

  4. I'm going to recreate this as a chemistry project.
    I will thoroughly cover the process I take to make a successful project, as well as provide a decent explanation (to the best of my knowledge) of what happens chemically, and why this works.

    This is so I could give you more information, and to see if what you think is correct or not.
    It's always good to have a project like this!

    Thank you for the post and the share, and I will contact you with more information as I go.

  5. If the teeth along with dental hygiene usually are not healthy along with in good shape it's not at all recommended to use one of the best whitening toothpaste solutions.
    Always check with your dentist if you're unsure. While whitening toothpastes are great to brighten your laugh,
    to keep it doing this you ought to maintain consistent and suitable brushing practices.
    This in reality is since important if not more important versus toothpaste itself.