Half a croissant, on a plate, with a sign in front of it saying '50c'
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sharpest knife ever

cuts through almost anything
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the blade is very thin, and yet within a network of tubes duct to the 'cutting edge'. through these, a continuous flow of gaseous hydrofluoric acid is fed. you will remember from high school chemistry this stuff will dissolve just about anything - thus breaking the chemical bonds that hold together whatever it is you want to cut. as a bonus, the surfaces subsequently cut will be left with a thin, teflon-like coating, easing the passage of the rest of the knife.
philmckraken, Jun 07 2004

h\Hydrofluoric acid poisoning http://www.nlm.nih..../article/002499.htm
The ingestion symptoms sound like too much trouble [Klaatu, Oct 05 2004, last modified Oct 21 2004]

[link]






       so it wouldn't dissolve the knife?
etherman, Jun 07 2004
  

       Where does the "thin, teflon-like coating" come from?
[etherman]: Not necessarily; the knife could be made from a type of plastic which is not attacked by hydrofluoric acid.
angel, Jun 07 2004
  

       You probably wouldn't want to eat your sandwiches afterwards!
MikeOliver, Jun 07 2004
  

       Dissolving something with acid is not the same as cutting it. While you could, presumably, eat through most anything given time, sharpness is usually associated with speed of cutting.   

       In terms of cutting edges that eat rather than slice through things, there are plenty out there that are plenty fast - laser light, high-pressure water, sand, etc.   

       While a high-pressure stream of HFl would no doubt couple mechanical with chemical erosion, I really don't think you would want to wield such a device manually.
DrCurry, Jun 07 2004
  

       Run it on plain air or water and mix fine sand into that. That way you cut by sand blasting. Gives your food a crunchy, beachy texture.
kbecker, Jun 07 2004
  

       Isn't hydrofluoric acid, the flouride ion part, particularly toxic?
bristolz, Jun 07 2004
  

       Also takes a high toll on the fine china. Not for carving the Thanksgiving roast goose.
jurist, Jun 07 2004
  

       Why not frikken laser beams? Give a sandwich that toasted edge to it.
sartep, Jun 08 2004
  

       Many of the objections here seem to based on the assumption that this knife would be used to cut food, although this is not implicit in the idea.
angel, Jun 08 2004
  

       HF is extremely toxic--even a small amount of skin contact can kill from the absorbed fluoride. (And it's interesting to look at the MSDS for a fluoride toothpaste: "Skin Contact: Using appropriate personal protective equipment, remove contaminated clothing and flush exposed area with large amounts of water. Obtain medical attention if skin reaction occurs, which may be immediate or delayed."
ldischler, Jun 08 2004
  

       thank you [angel]; that's why this is not in the 'cutlery' section (what are you others eating that would require the 'sharpest knife ever'? ewww...) this is a delicate lab tool for use by someone with gloves & goggles (or more likely a robot). the by-products of reaction with fluorine are very stable fluoride compounds: the 'teflon-like coating'... the HF flow is carefully controlled to release only as much as is required, into as small width as possible but giving a reasonable rate of 'cutting'. what i am clumsily groping for is a 'molecular knife'; something that cuts in a manner more sophisticated than brute force. ultimately i suppose you could use some type of atomic-force microscope, to displace individual atoms to each side. this would be maximally 'sharp', if perhaps a trifle slow
philmckraken, Jun 08 2004
  

       A molecular knife in the sense of what is currently used in AIDS research or the more fanciful type as portrayed in Snowcrash?
bristolz, Jun 08 2004
  

       *quickly googles 'snowcrash'*... sorry [bristolz] i haven't read it (what kind of nerd am i?). can it be more entertaining than the halfbakery?
philmckraken, Jun 08 2004
  
      
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