Imagine a ball point pen, filled not with liquid ink, but with a solid ink, similar to what solid ink printers use. A small battery powered heating element in the tip would keep enough ink liquid for the pen to operate.

In order to make heating not drain the battery too fast, the pen will need some high tech (thin) thermal insulation, probably an aerogel.

Because the ink cools as soon as it hits the paper, it doesn't smudge, even when the pen is being used by a lefty.

The prototype version would probably use crayons as their ink; production models would use something which smells less when it's hot.

Really advanced models might use some sort of solid dye sublimiation ink, and replace the ball point with a nozzle. An electronically controlled valve just above the nozzle would open only while the pen is in motion, and the nozzle is in contact with the paper.
-- goldbb, Oct 06 2009

I don't know if I'm comfortable with the idea of something that is rather hot being used to write with.
School kids'll have a field day branding each other.

Or do you mean that the heating occurs inside the pen? Thus rendering burning opportunities unlikely.
-- kaz, Oct 06 2009


Oh. And from the title I thought it would be a pen made of one stick of ink. Kind of like a pencil - but not, like a pen instead. Of ink.
-- normzone, Oct 06 2009


So... a crayon?
-- DrWorm, Oct 06 2009


//even when the pen is being used by a lefty.// Really? Because almost everything I write smudges...

Solid ink or not.
-- BouncyPaw, Oct 06 2009


Needs more lasers.
-- jutta, Oct 06 2009


I was also expecting an ink pencil. One way of achieving this is using a non-Newtonian fluid that is normally solid and a liquid when pressure is applied.
-- xaviergisz, Oct 07 2009


The halfbakery version of this would have to be some kind of highly oxidative (is that a new word?) solid that reacts with the paper leaving an ash residue that's suitably inert and non-smudging to serve as an ink.

Hey [8th] - got any oxidisers handy, perhaps one half of an hypergolic rocket fuel?
-- Custardguts, Oct 07 2009


Couldn't it work like a laser printer?
-- pocmloc, Oct 07 2009


//So... not a crayon.//

Even if it weren't a crayon, [normzone]'s concept would end up being pretty similar: a colored stick of a solid substance that puts marks on paper.
-- DrWorm, Oct 07 2009


// got any oxidisers handy //

Hmm. If the "solid" ink were mixed with microencapsulated oxidiser - hydrogen peroxide, maybe - then pressure on the tip would rupture the capsules, and the resulting reaction would melt the ink.

The trick would be to stop the reaction propagating spontaneously up the pen...... unless of course the thought of a pen suddenly exploding into flame pleases you.
-- 8th of 7, Oct 07 2009


//unless of course the thought of a pen suddenly exploding into flame pleases you.//

Well yes, it does, but that's not the point.

See I wasn't really interested in having *both* hypergolic components in the "pen" - just the oxidiser. The reducing agent would be the paper itself. But I assume you got that.

But from your idea: hey, autoigniting thermite pens. Yay!
-- Custardguts, Oct 07 2009


The logical extrapolation is to have a propelling pencil filled with a gritty matrix, and write on sandpaper treated with potassium chlorate and phosphorous.....
-- 8th of 7, Oct 07 2009


//a colored stick of a solid substance that puts marks on paper// - but that's the point: it would not leave marks on the paper, as long as it wasn't first heated. Thereby creating a mark that is non-soluble, as in: non-smearable save by a burning hand. [+]

Short number-juggling: There is about 50 micro-gram toner in one character from the laser printer, so let's double it for handwriting. Let's assume a specific heat capacity of 1kJ/(kg*K) and a heating of 100K for melting it -> 5mJ of heat per character. Assuming a 1/10th efficiency, the 1*10^4J in a standard 1.2V AA accumulator would last for 200 000 characters, which, frankly, is more than I usually write by hand over the course of a year. I like this more and more. To heat most efficiently, the lasers [jutta] demanded could be put to good use, minimizing the collateral heating: The laser sits on the back of the transparent stick, and on contact with paper it is switched on, using the stick as a waveguide. the stick-paper interface absorbs the energy , heating the stick at the point it touches the paper.
-- loonquawl, Oct 08 2009


Could heat be generated by friction of the roller?
-- Ling, Oct 08 2009


Or the heat from your fingers. (+)
-- 2 fries shy of a happy meal, Oct 08 2009


A glowing-hot writing desk?
-- pocmloc, Oct 09 2009


A thermally insulated pen, with all the heat being contained inside. On the outside of the pen, only the very tip would be hot.

The melting point of the ink would be 110F above human body temperature (so skin temp can't melt it), and would come out of the ball-point of the pen at that temperature. 110F is hot enough to be uncomfortable, but shouldn't be hot enough to cause heat injuries.

Because a ball point pen produces such a thin layer of ink, that ink should be able to cool quickly enough that it will re-solidify by the time someone touches it.

As for a crayon comparison... well, you could think of this as a high tech crayon, since the inks are, after all, waxes (just as they are in solid ink printers).

But it's a crayon with a much finer, more precise, line.
-- goldbb, Oct 11 2009


//the thought of a pen suddenly exploding into flame pleases you//
If it could make it mightier than the sword...
-- AbsintheWithoutLeave, Oct 11 2009


It can. Just sign off on the R&D budget ...
-- 8th of 7, Oct 11 2009


If the troublesome point is in applying heat, run the marked-up paper through your laser printer...or your toaster.
-- ldischler, Oct 11 2009



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