I wonder if...

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Senator
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Joined: Mon Oct 09, 2006 9:39 pm
Location: San Diego, California

I wonder if...

Post by Senator »

I noticed that one consideration for the eventual attempt at removal of the "space dust" is the use of a glass knife. I wondered if anyone looked at the use of an obsidian knife instead of glass, because obsidian is by far better than glass and a great deal sharper.

Obsidian is even used in some types of modern surgery because it is up to 100 times sharper and much smoother than their standard stainless steel scalpels. It creates less trauma to the skin. According to an article in Scientific American, "It is very sharp and very smooth at the microscopic level."


It seems to me that obsidian would be a much better choice. Anyway, I am tossing this out to see what others think about the idea and perhaps catch the attention of those who will be performing this delicate removal process. I truly want very much for the end result to be absolutely successful.

Just blame the interest on my archaeology days when I was messing around with cave dwelling technology that still works today. 8)

Groundling
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Joined: Sat Aug 05, 2006 6:55 pm
Location: Oregon, USA

knife

Post by Groundling »

Hi Senator;
That reverence was to a "glass needle" not a knife.
I don't know what the dimensions might be, but overall size is likely to be more important than cutting edge.
Groundling
I have met the enemy and he is us.
Pogo

Senator
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Location: San Diego, California

Re: knife

Post by Senator »

Groundling wrote:Hi Senator;
That reverence was to a "glass needle" not a knife.
I don't know what the dimensions might be, but overall size is likely to be more important than cutting edge. Groundling


Oops sorry, I forgot needle. The picture was provided that I believe was supposed to be the glass needle was all I remembered. It looked like a very bulky triangular shaped piece of glass, resembling more a crude attempt at making a knife than a needle. I know the picture was greatly magnified, but it still looks awkward for an instrument to be used in such a delicate operation.

If it were possible to form obsidian into a durable needle of the correct proportions, I believe it would be far superior to anything of glass. Might be worth checking out. 8)

fjgiie
DustMod
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Post by fjgiie »

Just some notes on this subject:

GLASS and Obsidian

-from the great wiki-(glass)
Glass is a uniform amorphous solid material, usually produced when the viscous molten material cools very rapidly to below its glass transition temperature, without sufficient time for a regular crystal lattice to form.
Common glass contains about 70-72 weight % of silicon dioxide (SiO2). The major raw material is sand (or "quartz sand") that contains almost 100% of crystalline silica in the form of quartz. Even though it is an almost pure quartz, still it may contain a little (<1%) of iron oxides that would color the glass, so this sand is usually enriched in the factory to reduce the iron oxide amount to <0.05%. Large natural single crystals of quartz are purer silicon dioxide, and they, upon crushing, are used for the high quality specialty glasses. At last, synthetic amorphous silica (practically 100% pure) is the raw material for the most expensive specialty glasses.

http://en.wikipedia.org/wiki/Obsidian
Obsidian is a type of naturally occurring glass. Despite its dark color,obsidian consists mainly of SiO2 (silicon dioxide), 70% or more. Obsidian is mineral-like, but not a true mineral because it is not crystalline. Because of the lack of crystal structure, obsidian blade edges can reach almost molecular thinness.

From Dr. Bryan Mendez
...micromanipulators and extremely sharp glass needles to machine the aerogel, and extract tracks in tiny doorstop-shaped wedges of aerogel that we call "keystones". Keystone picture

From Dr.Anna Butterworth
One very successful technique uses a computer controlled microscope, micromanipulaters and very sharp glass needles to carefully mine out tiny volumes of aerogel containing a whole Stardust track, without damaging the surrounding collector. We call them 'keystones' and they are held by tiny microfabricated silicon handles.
My colleagues Andrew Westphal, Christopher Snead and Zack Gainsforth have produced over 100 keystones from the Stardust comet aerogel.

From Update: 25 Sep 06 - CAPTEM Recommendations
Also, the possibility of keystoning using the microscope stage for motion and a glass needle fixed to the microscope head should be evaluated.

Groundling
Posts: 65
Joined: Sat Aug 05, 2006 6:55 pm
Location: Oregon, USA

knife 2

Post by Groundling »

Hi Senator;
Back to the original question: The image you saw in the the background information was of a wedge of aerogell containaining a track from the comet. (or an example) The needle I refered to is the needle that the example is suspended on.
A needle of that diameter (or smaller) would have been the machine tool used to extract that wedge.
Groundling
I have met the enemy and he is us.
Pogo

Domelsmith
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Joined: Sat Oct 07, 2006 1:53 pm
Location: Temple, Texas

Post by Domelsmith »

Greetings: Concerning obsidian knives for aerogel dissection. Modern flintknappers claim that with skill and luck you can get an obsidian blade with an edge one silicon dioxide molecule wide. There are a couple of knappers (ex.-Errette Callahan in Virginia) who make obsidian blades for delicate operations like cornea surgery, and the doctors brave enough to use them say they are sharper, easier to use and cause less scarring than conventional blades. Callahan insisted on having his rotator cuff surgery done with obsidian blades. Wouldn't it be interesting if one of mankind's oldest tools were used in one of our most technologically advanced endeavors?

ZackG
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Glass Needles vs. Diamond blades

Post by ZackG »

The reason we use needles instead of blades is that blades tend to stick to the aerogel at a microscopic level. Since the aerogel is so fragile, even such a small adhesion between the blade and the aerogel causes it to tear. So, while it is possible to make a shallow cut, as soon as the blade gets a ways into the aerogel (not deep enough to cut out cometary particles), then you start to tear the aerogel instead of cut it. Ick. Glass needles have a very small surface area due to the fact that, as Anna so succinctly put it, they are very sharp. We use glass needles to poke tens of thousands of microscopic perforations in the aerogel which define the edges of our cut. If the perforations are close enough together, the fragility of the aerogel actually causes it to crumble in the immediate (microscopic) vicinity, which then looks like a cut. We get a pretty good cut this way. The method of using glass needles was a breakthrough discovered by Christopher, and it totally revolutionized the way we cut aerogel.

Another approach, which works, is to use a diamond knife with ultrasound. The ultrasound causes the diamond knife to waggle just a few microns, and it essentially pulverizes the aerogel (again, on a microscopic level). The method is inferior for cutting keystones because the shape of the diamond knife greatly restricts the motion and types of cuts you can do. It also requires higher maintenance machinery, and the manufacture of the diamond blade itself, which is always a cause for gray hairs. And any hairs in a cleanroom are a bad thing. :-)

As far as the difference between obsidian and ordinary glass, we use glass because it is easier to shape into glass needles, and purer. We have to be careful not to introduce contaminants into the samples when we cut them out, and if the glass needle leaves some glass dust inside the aerogel, well, who cares -- the aerogel is glass too! With obsidian we would have to worry about the other 30% which consists of many of the same types of elements we're trying to discover in the samples. Also the sharpness of obsidian can be reproduced with glass -- it is the glass structure of obsidian which lends itself to creating the sharp edge.

I hope that's helpful! I may try to upload some images of some glass needles at some point here.
Zack Gainsforth
Space Sciences Laboratory
UC Berkeley

renu_krs
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Joined: Fri Aug 04, 2006 12:51 am
Location: Australia

my idea

Post by renu_krs »

This is my idea about extracting the particle. mm,, what i would do is, i would try to put the aerogel collector in a vessel and apply high pressure. As the aerogel collector is fragile, high pressure might loosen the collector and release the dust particles out of it...Then we can collect the particles once we remove the pressure out of it.... But i am not sure if high pressure will damage the particles.... i hope it won't.... As i am working on anti-solvent precipitation using supercritical fluids, i got this idea into my mind....Any comments folks????

greuti
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Joined: Fri Aug 11, 2006 10:11 am
Location: Switzerland

Post by greuti »

I hope that's helpful! I may try to upload some images of some glass needles at some point here.
Yea it is, thanks for the explanations!
It would be very interesting to get some images of them. Maybe, if possible, even during using of them.

@renu_krs:
Hi, what do you mean by "loosen the collector and release the dust particles"? Do you mean the areogel shatters to a heap of thousands and thousands of glass pieces in this way, wherein you then might find dust particles? It sounds destructive :) (and contaminative) - Anyway you have to search them in the heap by microscope again since they are that small.

ZackG
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Needles

Post by ZackG »

Show and tell!

I took one of our needles (yes this one was actually used, and was at the end of it's life), and put it over the word "Liberty" on a quarter. Since we have an international community, a quarter is 24 mm across, or just under 1 inch, and the word liberty is about 7 mm or roughly 1/4 inch from L to y.

So, here's the first image:

Image

Now, let's zoom in a little more on that needle point...

Image

Not close enough yet...

Image

Sorry, that's the best this microscope will do! :shock:
Zack Gainsforth
Space Sciences Laboratory
UC Berkeley

RVideo
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Joined: Wed Oct 25, 2006 5:53 am

Post by RVideo »

Sheesh. If you poke your finger with one of those, does it actually register?

greuti
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Location: Switzerland

Post by greuti »

RVideo wrote:Sheesh. If you poke your finger with one of those, does it actually register?
You would it probably register, but even less than an acupuncture needle (diameter of 0,20 - 0,30mm).

(Wow!) The size (diameter) of the needle and its tip is amazingly fine/thin! That hair's diameter, as compared to the quarter here, is circa 55 microns (0,055mm) according the size of the image (480x360 microns = pixels).

For comparison I put both images of the quarter parts (with needle and hair) together and brightened it. The diameter of the "I" and the "E" part on the quarter seems to be about the same - so I had not to resize them (right?).
So what's the diameter of the needle just around its tip?! Can't believe it that one can poke with it in the aerogel. On the other hand it shows how fragile this aerogel really is.

(click on for original size)
Image

ZackG
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Needle tip diameter

Post by ZackG »

I know that Christopher took one of our needles down to the electron microscopy lab on campus one day to look at just how sharp the tip was. He was not actually able to resolve the tip even with the electron microscope we had available. But in lieu of tracking down a better microscope, or using a different measurement technique I'd venture a guess that it is on the nanoscale. Glass knife edges are known to be commonly on the order of tens of nanometers. We're not using the same process, but I'd guess we're in the same ballpark nonetheless. For those of you who are interested here is where to go to get the materials to make microneedles: http://www.sutter.com/products/micropipette_fab.html They're selling devices for manufacturing micropipettes which are used by biologists to inject DNA into cells as part of a little upstart science by the name of genetic engineering. :lol: The micropipettes are regularly about 300 nm and they have a hole in the middle. Hence, I yield my guess that our tips are smaller than 300nm by quite a bit. Maybe 30? Maybe 100 nm? Something like that.

Yet, despite their sharpness, they DO hurt. Of course, that's probably because they're not being inserted by an acupuncture specialist, but quite by accident. :? However, they don't hurt badly -- they are much less annoying than, say, going to the doctor. One word of advice, though, if you do prick yourself using one, give up trying to find the splinter in your finger under a microscope. You just won't find it...
Zack Gainsforth
Space Sciences Laboratory
UC Berkeley

jsmaje
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Location: Manchester UK

Post by jsmaje »

The five-barrelled Pyrex micropipettes I used for my PhD way back in 1974/6 had overall tip diameters of down to 3 microns, with individual barrel diameters of about 1 micron...so I guess their wall-thicknesses must have been something like 250nm. And this was after they had in fact been broken back (for practical reasons) from the potentially-even-finer tips readily obtainable, as Zack points out.

BTW, what do you make of this from the Sutter site?
We have drawn optical fiber tips ranging from less than 10 microns to more than 5 microns (my italics).
Eh? So that's between 5-10 microns then?... :roll:

ZackG
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Post by ZackG »

jsmaje wrote: BTW, what do you make of this from the Sutter site?
We have drawn optical fiber tips ranging from less than 10 microns to more than 5 microns (my italics).
Eh? So that's between 5-10 microns then?... :roll:
Which model are you looking at? On the page I gave, about halfway down I see the P-30 will pull to 0.3 microns. I think it depends on which model you're using, how you configure it, and whether you're using hollow core needles or solid core needles. Most of the micropipette guys in biology want the needles to have a hollow core so they can inject/extract liquids through the needle. In this case, an ideal size would probably be a few microns for most purposes because the smaller the needle gets the harder it is to push liquid through it. In our case, we would rather have a solid core to get a finer point.
Zack Gainsforth
Space Sciences Laboratory
UC Berkeley

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