[dentstudent (OP)]

without it snapping, would you feel it?

[neilep]

If it's made from a big fat atom then you might.....!!..then again....I don't see how you could feel it !...presumably it's just the tip of the needle which is that thin yes ?...still...the shank would still be thin though....amazing !!!!

[another_someone]

I don't think the problem is merely the snapping of the needle (I assume this could not be a hollow needle, as you could not get a hole in at atom); but how would you create a rigid structure in one dimension (i.e. with only a single row of atoms) - you need a 3 dimensional structure that will hold the atoms rigidly in place.

[Heronumber0]

dentstudent - does it not depend on the threshold pressure? The closest I could come to a figure for the pressure is the somewhat mysterious 0.23 gf/cm2 from
http://www.alab.t.u-tokyo.ac.jp/~shino/research/pdf/icat01.pdf. So if you could scrape or jab the skin at that pressure, then the sensory neurones surrounding the skin pressure receptor cells (aka cutaneous mechanoreceptors) would register a 'hit'.

In a scanning tunnelling electron microscope used to scan the ordered surfaces of e.g. gold, silver etc... the stylus tip is one atom thick.  The stylus normally used by physiologists is in the magnitude of 100 micrometers wide which is thousands of times bigger.  Does this help?

[dentstudent (OP)]

Thanks for all the answers!

Hero#0, thanks too - it's a good point.

Let's make it purely hypothetical. Assume that you can make a need with a shaft 1 atom across. If you rested it against the surface of the skin, would it just slide in? Would it be small enough to fit between the nerve endings and therefore you wouldn't register any pain?

[Heronumber0]

ds - good point (no pun intended). However, only the tip would slide in, the rest of the tip would have to be bigger than one atom to support this needle surely?

[dentstudent (OP)]

ds - good point (no pun intended). However, only the tip would slide in, the rest of the tip would have to be bigger than one atom to support this needle surely?

That's why I suggested it to be purely hypothetical........How many atoms would be needed to make a viable needle?

[another_someone]

That's why I suggested it to be purely hypothetical........How many atoms would be needed to make a viable needle?

The closest we have, and probably an indication of how close we will get, is carbon nanotube, in the order of a nanometre wide.  At present, these can be up to a few millimetre long (the can be joined in composite structures, but these will not be as stiff), but I see no reason why in theory at least one could not extend a single nanotube without a clear limit.

[dentstudent (OP)]

The closest we have, and probably an indication of how close we will get, is carbon nanotube, in the order of a nanometre wide.  At present, these can be up to a few millimetre long (the can be joined in composite structures, but these will not be as stiff), but I see no reason why in theory at least one could not extend a single nanotube without a clear limit.

So, a nanometre (1/millionth metre?) across. What would its effect be when pushed into the skin? Would it be felt?

[another_someone]

So, a nanometre (1/millionth metre?) across. What would its effect be when pushed into the skin? Would it be felt?

I suspect you would not feel a thing - although one problem with structures that small, they can actually pierce a cell wall, and enter a cell.  Very useful if you are trying to do GM, as it is an alternative to using viruses as a means of having foreign genes enter a cell, but potentially carcinogenic if used without care.

[dentstudent (OP)]

I suspect you would not feel a thing - although one problem with structures that small, they can actually pierce a cell wall, and enter a cell.  Very useful if you are trying to do GM, as it is an alternative to using viruses as a means of having foreign genes enter a cell, but potentially carcinogenic if used without care.

ok, thanks. I've just had thought about mosquitos - I don't think that they inject any sort of anaesthetic when they "bite", and I only notice the bite when it starts itching. So, how wide are their probosciss (plural spelling?). Probosci? Where does the threshhold of feeling the injection commence?

[another_someone]

ok, thanks. I've just had thought about mosquitos - I don't think that they inject any sort of anaesthetic when they "bite", and I only notice the bite when it starts itching. So, how wide are their probosciss (plural spelling?). Probosci? Where does the threshhold of feeling the injection commence?

I had assumed the do anaesthetise - they certainly pump coagulants in, and vampire bats do anaesthetise.

http://www.surviveoutdoors.com/reference/mosquito.asp

When the mosquitoes sword like mouth pierces our skin we rarely feel pain. The mosquito uses an anesthetic in its saliva that is injected in the tissue. This can cause a local reaction usually of redness, and a wheel with intense itching.

Rarely do mosquito bite reactions occur in children less than 1 year old due to their levels of antibodies. The bite itself is our bodies response to antibody complexes and histamine. The bite will go away in a few days. In rare situations it may last for a couple of months.

[dentstudent (OP)]

Oh, ok. Discount that thought then......