Audibly crushing a diatom

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Hobbyst46
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Audibly crushing a diatom

#1 Post by Hobbyst46 » Sun Jul 12, 2020 3:42 pm

I have been cleaning and processing some spring diatoms. Among them there was a single centrales, tentatively Thalassiosira (or Biddulphia), which in 3D looks like a cylindrical jar of diameter ~50um. The first image is a valve view.
I then carelessly switched into the 100X without oil, just to see... And heard a "crack"!
Why, the objective has smashed the cover slip, I thought, so either of them is shattered or scratched - so switched back into the dry 40X - and the only fractured object is the diatom...
Images are phase contrast, 40X0.75 objective, resized and cropped, adjust brightness in post processing.
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diatom (stack of 4).jpg
diatom (stack of 4).jpg (59.59 KiB) Viewed 2182 times
crushed diatom.jpg
crushed diatom.jpg (86.63 KiB) Viewed 2182 times
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Re: Audibly crushing a diatom

#2 Post by MichaelG. » Sun Jul 12, 2020 4:36 pm

That’s rather spectacular !!

Could you repeat it with a load cell in the system ? :geek:

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Re: Audibly crushing a diatom

#3 Post by Hobbyst46 » Sun Jul 12, 2020 5:58 pm

The mechanical strength of frustules has been studied, and example:
https://carabthompson.wordpress.com/201 ... oms-shell/
From which I take it that the force is of the order of 10nN (nano-newtons)... they pressed it with a fiber
The fiber I am now using to hunt the frustules and pick them up is a ~5-10um glass fiber. It flexes like a leaf spring when I press on the diatom, and does not break it.
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Re: Audibly crushing a diatom

#4 Post by MichaelG. » Sun Jul 12, 2020 6:46 pm

Thanks for the link

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Re: Audibly crushing a diatom

#5 Post by 75RR » Mon Jul 13, 2020 4:19 am

.. And heard a "crack"!
I know that awful feeling when one hears that sound. A couple of times it was a diatom ... and once an actual cover slip!
Hobbyst46 wrote:
Sun Jul 12, 2020 5:58 pm
The mechanical strength of frustules has been studied, and example:
https://carabthompson.wordpress.com/201 ... oms-shell/
Nice link. Does seem that the site has petered out, pity.
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Re: Audibly crushing a diatom

#6 Post by Hobbyst46 » Mon Jul 13, 2020 5:29 am

MichaelG wrote:...
75RR wrote:
Mon Jul 13, 2020 4:19 am
https://carabthompson.wordpress.com/201 ... oms-shell/
Nice link. Does seem that the site has petered out, pity.
"Petered out" ?? means it is not open for reading because of its age ?
Here is a citation from it {Hamm et al, Nature volume 421, pages841–843(2003)} - from the Methods section:
Glass needle tests
Diatoms were cultured at 0 °C (F. kerguelensis) and 15 °C (T. punctigera, C. granii) under moderate light intensities. Microneedles were drawn from borosilicate glass with a micropipette puller. Microneedles were of cylindrical shape and showed no visual irregularities. These microtools were mounted in a micromanipulator. Experiments were performed in a measurement chamber filled with sea water on the stage of an inverted light microscope equipped with long-distance lenses and differential interference contrast optics. Micrographs were recorded with a charge-coupled device (CCD) camera, stored on videotape, and analysed using the image processing software NIH-Image. Glass needles were calibrated with atomic force microscope (AFM) cantilevers of known spring constants, which resulted in needle deflection as linear functions of applied forces. The pressure on the diatoms was gradually increased until the cells broke. Thus, by measuring the deflection of the needle in the relaxed state and directly before the cells broke, we could determine the maximal forces the cells were able to resist. Thicker and stiffer needles, which exceeded the range where the procedure described above was practicable, were calibrated by directly relating their deflections to forces that were measured on a microbalance. On the basis of the symmetries of the diatoms, we applied pressure with a glass microneedle from three different positions: (1) along the girdle bands, (2) across the girdle bands, and (3) across the centre of the valves.


P.S. It seems that my previous citation of the force needed to break the frustules was grossly incorrect: it takes tens of nM to just deform the diatom. Crushing takes hundreds of micro-Newtons!! The diatoms are strong.
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Re: Audibly crushing a diatom

#7 Post by 75RR » Mon Jul 13, 2020 6:44 am

Hobbyst46 wrote:
Mon Jul 13, 2020 5:29 am

"Petered out" ?? means it is not open for reading because of its age ?
I was referring to the fact that there are only 5 posts on the site, all dating from 2014.
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Re: Audibly crushing a diatom

#8 Post by Hobbyst46 » Mon Jul 13, 2020 7:45 am

75RR wrote:
Mon Jul 13, 2020 6:44 am
Hobbyst46 wrote:
Mon Jul 13, 2020 5:29 am

"Petered out" ?? means it is not open for reading because of its age ?
I was referring to the fact that there are only 5 posts on the site, all dating from 2014.
The Nature 2003 article nevertheless is apparently of interest, has been cited 78 times in journals.
There is a later publication
" Size and biomechanic properties of diatom frustules influence food uptake by copepods "

By:Friedrichs, L (Friedrichs, L.)[ 1 ] ; Hornig, M (Hoernig, M.)[ 1 ] ; Schulze, L (Schulze, L.)[ 1 ] ; Bertram, A (Bertram, A.)[ 1 ] ; Jansen, S (Jansen, S.)[ 1 ] ; Hamm, C (Hamm, C.)[ 1,2 ]
View Web of Science ResearcherID and ORCID
MARINE ECOLOGY PROGRESS SERIES, Volume: 481, Pages: 41-51, DOI: 10.3354/meps10227, Published: 2013
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Re: Audibly crushing a diatom

#9 Post by 75RR » Mon Jul 13, 2020 8:28 am

Hobbyst46 wrote:
Mon Jul 13, 2020 7:45 am
75RR wrote:
Mon Jul 13, 2020 6:44 am
Hobbyst46 wrote:
Mon Jul 13, 2020 5:29 am

"Petered out" ?? means it is not open for reading because of its age ?
I was referring to the fact that there are only 5 posts on the site, all dating from 2014.
The Nature 2003 article nevertheless is apparently of interest, has been cited 78 times in journals.
There is a later publication
" Size and biomechanic properties of diatom frustules influence food uptake by copepods "

By:Friedrichs, L (Friedrichs, L.)[ 1 ] ; Hornig, M (Hoernig, M.)[ 1 ] ; Schulze, L (Schulze, L.)[ 1 ] ; Bertram, A (Bertram, A.)[ 1 ] ; Jansen, S (Jansen, S.)[ 1 ] ; Hamm, C (Hamm, C.)[ 1,2 ]
View Web of Science ResearcherID and ORCID
MARINE ECOLOGY PROGRESS SERIES, Volume: 481, Pages: 41-51, DOI: 10.3354/meps10227, Published: 2013
Not a criticism, just said it was a pity that the site was no longer active as the articles look interesting.
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Re: Audibly crushing a diatom

#10 Post by MichaelG. » Mon Jul 13, 2020 6:13 pm

.

The letter to ‘Nature’ is very interesting, and the FE modelling of Diatoms most impressive ... but I was surprised by one stated assumption [near the top of the second column] regarding the testing.
.
Assuming that the glass needle pressed on an area of 100 [square micrometres] ...
.
note: I have stated the units in text, because copy & paste corrupts the original
.
Question: On what basis did they make that assumption ?

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Re: Audibly crushing a diatom

#11 Post by 75RR » Mon Jul 13, 2020 6:53 pm

MichaelG. wrote:
Mon Jul 13, 2020 6:13 pm
.

The letter to ‘Nature’ is very interesting, and the FE modelling of Diatoms most impressive ... but I was surprised by one stated assumption [near the top of the second column] regarding the testing.
.
Assuming that the glass needle pressed on an area of 100 [square micrometres] ...
.
note: I have stated the units in text, because copy & paste corrupts the original
.
Question: On what basis did they make that assumption ?

MichaelG.
10 µm width of glass needle and assumed 10µm length of contact surface?
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Re: Audibly crushing a diatom

#12 Post by MichaelG. » Mon Jul 13, 2020 8:13 pm

75RR wrote:
Mon Jul 13, 2020 6:53 pm
MichaelG. wrote:
Mon Jul 13, 2020 6:13 pm
.
Question: On what basis did they make that assumption ?

MichaelG.
10 µm width of glass needle and assumed 10µm length of contact surface?
.

The contact patch of a motorcycle tyre on tarmac is only about the size of a credit card.
... and that’s a soft object contacting a relatively smooth, flat, surface.

A hard glass rod, contacting a complex shape made from silica would, I suggest, only make a few ‘point contacts’ [theoretically, only three] until such time as significant distortion has taken place.

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Re: Audibly crushing a diatom

#13 Post by Hobbyst46 » Mon Jul 13, 2020 8:29 pm

75RR wrote:
Mon Jul 13, 2020 6:53 pm
MichaelG. wrote:
Mon Jul 13, 2020 6:13 pm
.

The letter to ‘Nature’ is very interesting, and the FE modelling of Diatoms most impressive ... but I was surprised by one stated assumption [near the top of the second column] regarding the testing.
.
Assuming that the glass needle pressed on an area of 100 [square micrometres] ...
.
note: I have stated the units in text, because copy & paste corrupts the original
.
Question: On what basis did they make that assumption ?

MichaelG.
10 µm width of glass needle and assumed 10µm length of contact surface?
Good, but still assuming...
The diameter of their needle appears to be ~18um;
And the frustule is elastic, so it flexes whether pressed from the valve or the girdle...
Plus the surface is rough on the micro-scale, not totally smooth;
Bewildering question, Michael ! I adopt Glen's answer, for simplicity and accuracy !
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Re: Audibly crushing a diatom

#14 Post by 75RR » Mon Jul 13, 2020 8:30 pm

MichaelG. wrote:
Mon Jul 13, 2020 8:13 pm
A hard glass rod, contacting a complex shape made from silica would, I suggest, only make a few ‘point contacts’ [theoretically, only three] until such time as significant distortion has taken place.
Given that this was a destruction test, I would say that significant distortion had taken place.
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Re: Audibly crushing a diatom

#15 Post by MichaelG. » Mon Jul 13, 2020 8:46 pm

75RR wrote:
Mon Jul 13, 2020 8:30 pm
MichaelG. wrote:
Mon Jul 13, 2020 8:13 pm
A hard glass rod, contacting a complex shape made from silica would, I suggest, only make a few ‘point contacts’ [theoretically, only three] until such time as significant distortion has taken place.
Given that this was a destruction test, I would say that significant distortion had taken place.
... but they were calculating the applied loads, in Newtons per [area], so the instantaneous load which initiates the cracking should start very high, and rapidly reduce as the contact area increases.

Not worth worrying about it though ... it was just a thought.

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Re: Audibly crushing a diatom

#16 Post by 75RR » Mon Jul 13, 2020 8:59 pm

MichaelG. wrote:
Mon Jul 13, 2020 8:46 pm
... but they were calculating the applied loads, in Newtons per [area], so the instantaneous load which initiates the cracking should start very high, and rapidly reduce as the contact area increases.

Not worth worrying about it though ... it was just a thought.
Mine was just a suggestion ... I wonder if it would be possible to contact the participants in the test.
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Re: Audibly crushing a diatom

#17 Post by MichaelG. » Mon Jul 13, 2020 9:04 pm

I might try that ... but as it was published in 2003, they may have all moved-on by now.

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Re: Audibly crushing a diatom

#18 Post by MichaelG. » Thu Jul 16, 2020 7:51 pm

UPDATE:

I found the ‘corresponding author’ Dr. Christian Hamm, and eMailed him [more in hope than expectation]
.
Dear Dr. Hamm

I am an amateur microscopist with a broad interest in mechanics.

A friend on the ‘microbehunter’ forum recently posted a link to your 2003 letter in Nature

viewtopic.php?f=10&t=9865

We found this very interesting and informative; but I posed a question [at post #10], to which we have not yet found a satisfactory answer ...

I would be most grateful if you could advise.
.
I am delighted to say that he responded very promptly and helpfully:
.
Hi Michael,

thank you for the very interesting discussion! In fact, your description of the cracking noise is most interesting, we have not heared it in this form, but in our system, we used micrmanipulators and a screen to monitor the mechanical tests, so the distance to the cracking diatoms was, most likely, higher. Although it is possible to generate very annoying noises with surprisingly little effort, your observation underlines that substantial energy is required to destroy a frustule. And the picture of the frustule which broke in many places suggests that the stress has been high in many places at the same time, which indicates a good stress distribution/ energy dissipation (as is wanted in a crash box of a car).

Concerning the forces, both values which you mentioned are correct, in these experiments, we reached > 700 µN for the intact diatoms, the girdle bands were deformed much more easily (at ca 36 nm), these single girdle bands were mainly used to get a first impression on the material properties, in this case the e-modulus, of the diatom silica.

I may have to apologize for the 100µm2 assumption - this is a very rough estimate - the purpose was only to transform the minute forces into something which is easier to relate to - such as pressure. As has been supposed in your discussion, the background was the observation that just before failure, the needle appeared to be (visibly) in contact with a patch which had a length of ca 10µm, and for an estimate, we found it was not too unrealistic to use the same length for the other dimension of the contact area. Of course, if you do not have FULL contact because of complex surface structures in some diatoms, pressure would be higher. Anyway, the reliable (measured) values are the ones for the forces.

Although the study is now quite old, there has been not too much progress concerning the knowledge on total diatoms as mechanical systems. However, very interesting results have been published on the material properties of diatoms (Topal et al., 2020, Vorland, 2014) and on diverse other aspects. We have focussed on technology transfer for the last ca. 15 years, but since we founded a startup (ELISE GmbH), we have now the ressources for serious activities in fundamental reserach again.

all the best for your future observations and experiments!

Christian

P.S. I have a profile on Google Scholar if you were interested in my publications
.

What a pleasure it is to deal with people like this !

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Re: Audibly crushing a diatom

#19 Post by 75RR » Thu Jul 16, 2020 7:57 pm

MichaelG. wrote:
Thu Jul 16, 2020 7:51 pm
What a pleasure it is to deal with people like this !
Very true! Restores ones faith in people :)
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Re: Audibly crushing a diatom

#20 Post by Hobbyst46 » Thu Jul 16, 2020 8:13 pm

Thanks 75RR and MichaelG for the discussion and consultation,
Nice to know that the tiny hobby experiment is being appreciated by a professional in the field.
And that our combined thinking about the contact area was rational.

BTW: in another very recent post I presented photos of diatoms of the same type together with what I believe to be a girdle - or half-gridle - a semi-circular ribbon band. These bands are very thin, quite transparent, and flexible. They are as abundant as the centric frustules. They strongly cling to the fiber, so are easily picked up from the storage slide, and difficult to place on the target slide. I Wonder how they will look when finally mounted, in the future.
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Re: Audibly crushing a diatom

#21 Post by MichaelG. » Thu Jul 16, 2020 10:53 pm

Too many 'projects'

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Re: Audibly crushing a diatom

#22 Post by 75RR » Fri Jul 17, 2020 3:17 am

Neat links!

Have downloaded Nanomaterials + Armor: Why, When and How :)
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Re: Audibly crushing a diatom

#23 Post by MichaelG. » Sat Jul 18, 2020 5:54 am

Too many 'projects'

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Re: Audibly crushing a diatom

#24 Post by 75RR » Sat Jul 18, 2020 7:25 am

MichaelG. wrote:
Sat Jul 18, 2020 5:54 am
You may also like : https://www.researchgate.net/publicatio ... _Existence

MichaelG.
Thanks for that.

By the way, just uploaded a video that shows what diatoms have to put up with.
Last edited by 75RR on Sun Jul 19, 2020 3:50 pm, edited 1 time in total.
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Re: Audibly crushing a diatom

#25 Post by Sabatini » Sun Jul 19, 2020 3:47 pm

Very interesting, thanks for the information.

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Re: Audibly crushing a diatom

#26 Post by Charles » Tue Jul 21, 2020 10:56 pm

I would think that different species will have different mechanical strength. Some frustules I can push a glass needle through and others can break my glass needle. No wonder they can last for thousands of year and come out cleaned like they first died and floated to the bottom of the water column.

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Re: Audibly crushing a diatom

#27 Post by KurtM » Wed Jul 22, 2020 1:08 am

I would think that different species will have different mechanical strength.
I agree absolutely, Charles. I've studied the Cylindrotheca genus of diatoms in part because they're so lightly silicified that most cleaning processes, even the gentler ones, dissolve them utterly and leave no trace! Even as living things the frustules are so delicate they're flexible, and often bend in the process of making "raw" slides of unprocessed specimens. On the other end of the spectrum is something like Auliscus, which is built like an ashtray (remember ashtrays?) and sports something like a 14:1 thickness ratio.
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Re: Audibly crushing a diatom

#28 Post by Hobbyst46 » Wed Jul 22, 2020 8:48 am

Charles wrote:
Tue Jul 21, 2020 10:56 pm
I would think that different species will have different mechanical strength.
Same as my (relatively short-term) experience.
Some frustules I can push a glass needle through and others can break my glass needle...
My glass fiber is uniformly thick (5-10um) - and very long - ~3mm. Not because I preferred it, just what I accomplished. Some authors recommend a short and pointed needle, and your inspiring posts and videos, Charles, indeed demonstrate its effectiveness in the right hands. My first move towards a diatom is try to attach it from above, so it hangs from the fiber tip. When that goal is achieved, the diatom remains intact. Otherwise, sometimes scraping leads to fracture of the diatom.

However, many of them, especially the short (<50um) pennates, strongly cling to the slide. I tried breathing on them to increase humidity and lower electrostatic forces, but to no avail. Then I use the fiber as a spade or blade, press under the diatom and apply lever action. Result : (1) golf-ball effect - diatom jumps and flies and lands elsewhere; or (2) amazing flexing of the fiber, it almost becomes a semi-circle, the diatom stands its ground and I give up; or (3) fracture of the diatom.
The remedy is a ground-glass donor slide instead of an ordinary smooth transparent one. Seems to better the situation, at least somewhat.
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