Black Silicon Slices and Dices Bacteria 78
Zothecula writes "Originally discovered by accident in the 1980s, black silicon is silicon with a surface that has been modified to feature nanoscale spike structures which give the material very low reflectivity. Researchers have now found that these spikes can also destroy a wide range of bacteria, potentially paving the way for a new generation of antibacterial surfaces."
Durability? (Score:5, Interesting)
They found similar structure on insects' wings (Score:5, Interesting)
From the TFA:
" ... the wings of the cicada Psaltoda claripennis could shred certain types of rod-shaped bacteria ... "
... the wings of the Diplacodes bipunctata or Wandering Percher dragonfly were even more deadly, killing both rod-shaped and spherical bacteria ... "
"
I am very curious.
Since the structures on the WINGS of the insects, do they have some yet-to-be-discovered aero-dynamic functionality, apart from their ability to shred bacteria ?
Re:They found similar structure on insects' wings (Score:5, Interesting)
If these are particularly small wings, I suppose that all of these nano spikes might provide some kind of static energy lift similar to what was recently discovered in spiders.
Re:They found similar structure on insects' wings (Score:5, Interesting)
The silicon structures they were looking at were in the 500nm range, the dragonfly ones ~240nm. That's a huge amount of additional surface area, and on a scale where interaction with gas molecules will probably owe a vexing and deeply unhelpful amount to causes that we normally leave to the chemists, rather than idealized fluid behavior or largely ideal gas kinetic behavior...
Re:They found similar structure on insects' wings (Score:5, Funny)
I was going to mod you up, but they don't have an option for "You just made my head assplode"
Re:They found similar structure on insects' wings (Score:5, Interesting)
(If it turns out that the bugs are capable of using cell membrane potentials to selectively induce dielectric polarization of the air passing over selected parts of the wing surface, or something else verging on plain cheating, I say we back away slowly and let them take over.)
I'll have a go (Score:5, Funny)
I wish the best of luck to whoever gets to model the behavior of a mixed (mostly) nonpolar gas interacting with a dense, more or less randomly packed, array of 240nm spikes, composed of some sort of complex biological polymer arrangement, at the boundary of the (already complex enough) interaction between an insect wing and the surrounding fluid.
Let us suppose a perfectly spherical spike in a vacuum...
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one word:
Bumblebees.
That is all.
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"If it turns out that the bugs are capable of using cell membrane potentials to selectively induce dielectric polarization...."
A most wonderful wicked question. I'm wondering, given what their metabolism is like, if they'd really need to flap their wings at all - or just do so for added effect, flying like a normal winged critter.
Depending on how this pans out, not only do we get nifty new knowledge about an area of which we mostly know nothing, but end up with great biocide wipes and, make it big enough,
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That said, w
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Well, you got the science on me; I had just been doing so old-fart musing via still-surviving gee-whiz enthusiasm and pulled some stray bits out of my, um, odd niches of shelving in the mustier parts of brain. Just now I've come from Wikipedia and a quick half-hour of reading this and that; turns out O2 has a Van der Waals radius of 152pm. If there might be any interaction at, say, the tip of a spike and the adjacent bits of atmosphere, beats me. It's been too long since I've used any of this stuff, so c
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From the TFA:
" ... the wings of the cicada Psaltoda claripennis could shred certain types of rod-shaped bacteria ... "
" ... the wings of the Diplacodes bipunctata or Wandering Percher dragonfly were even more deadly, killing both rod-shaped and spherical bacteria ... "
I am very curious.
Since the structures on the WINGS of the insects, do they have some yet-to-be-discovered aero-dynamic functionality, apart from their ability to shred bacteria ?
My first thought was "I wonder how the structure changes the reflection of sound?"
Maybe the wings are deadened for sound in defense against bats. (Which would create massive selective pressure, bats are extremely efficient predators of insects.)
I could understand how even the smallest bacterial infection on an insect wing could compromise it's owner, but it seems like those structures would be everywhere, because a bacterial infection ANYWHERE can compromise it's owner. So why wouldn't the same structur
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the scales of the sharks do: They create micro-turbulences that act as a sort of physical anti-friction layer, AFAIK this properties were used by the aircraft industry already.
So that these structures may have a similar function in the insect's wings
Durability - big problem with many exotic surfaces (Score:4, Interesting)
Durability of an exotic surface structure can be a problem. An example is ultra-hydrophobic coatings. (Now available at retail as Rust-Oleum NeverWet.) They really do repel liquids so thoroughly that coated surfaces can't even get muddy. But they seem to wear out quickly. There are YouTube videos showing that stuff working for ten minutes, then failing. But maybe someone will come up with an improved coating that's tougher.
"Paint-on solar cells" also fall into this category.
Re:Durability - big problem with many exotic surfa (Score:5, Interesting)
Marine anti-fouling coatings have similar trouble: they've tried to make less toxic ones, with specially crafted surface geometry that resists mooring by marine organisms; but the minute it starts to wear out, boom, stuff growing. Even the ones that are laced with ghastly organometallic biocides eventually leach enough to lose effectiveness and have to be stripped and re-applied.
(though, speaking of anti-fouling coatings, if microspike-structures are aerodynamic enough for insect wings and brutally biocidal, I suspect that the world's marine shipping industry would fight like dogs to give you their money if you could paint this stuff on...)
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the world's marine shipping industry would fight like dogs to give you their money if you could paint this stuff on...
There's two ways to do it:
1. http://en.wikipedia.org/wiki/Reactive_ion_etching [wikipedia.org]
2. Pulsed lasers
AFAIK, this only works on silicon, which doesn't strike me as something that's durable enough for marine applications.
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As you say if
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You fight wearing out by making internal structure such that it sheds in layers which reveal new surface-like layers beneath them as they fall off. For that, you need to design connection points between layers to most probably fail (to be weakened) first. Like a bed of sharp nails connected by its fine points to another bed of nails above, and that one with another one above it ... etc.
Radar (Score:2)
Can I get this for my car, to absorb radar and lidar?
Re:Radar (Score:5, Informative)
Then, I'd suggest you research some methods to deal with the increase of temperature in your car, due to the absorbtion of light in the spectral range 350–1150 nm (near infrared to near UV) - you'll need to dissipate approx 1 kW for each square meter of absorbing surface [wikipedia.org]
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You could power the car with it. ;-)
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You could power the car with it. ;-)
Using the car's interior as the working volume for the expansion of hot gases... that would be an idea!
Re:Radar (Score:4, Interesting)
I see potential for ultra-efficient solar hot water.
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Wrong size scale for radar, which would require ~ 1 cm scale features (which might be difficult to combine with reasonable aerodynamic efficiency). Or, you need to specially shape your entire car --- like the crazy angular surfaces of funny-shaped stealth aircraft --- to avoid any surfaces with a direct reflection path back to the transmitter. I suppose a super-black car might confound lidar; even if it didn't, at least it would look pretty cool. Until some truck sideswipes you at night because they didn't
Re:Radar (Score:5, Funny)
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"Wrong size scale for radar, which would require ~ 1 cm scale features (which might be difficult to combine with reasonable aerodynamic efficiency)"
Embed the whole thing in radar-transparent plastic or similar material.
Might still be too heavy for aircraft.
sounds like tiny little bacteria-stabbing spikes (Score:4, Interesting)
"This structure generates a mechanical bacteria killing effect which is unrelated to the chemical composition of the surface," says Professor Crawford, who is Dean of the Faculty of Life and Social Sciences at Swinburne.
Very low level abrasive... I wonder if and how that might serve as a soap.
Re:sounds like tiny little bacteria-stabbing spike (Score:5, Informative)
Soap also serves as a pretty good soap. I suspect the fine size scale of these structures, on a rigid silicon backing, would't be too good at reaching into very much of the rugged mountainous topography (on a bacteria's scale) of human skin.
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What you are describing sounds like a waterslide. ;)
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A long waterslide flowing with an abrasive grit slurry, however, might not be the most fun kind of waterslide.
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Even when they're not used for cleaning hands materials like this are useful for keeping surfaces cleaner to reduce germ transmission. I've read that simple brass and other copper alloys also have similar properties [copper.org] and there was a brief campaign to use it for things such as door handles in hospitals. Brass would most likely be much more economical to produce and has the added benefit of being very easy to recycle.
a concern (Score:2, Interesting)
As it wears down or chips away over time, can the nano particle surface become airborne and become inhaled having similar issues like asbestos?
Re: a concern (Score:5, Interesting)
In short: no.
Essentially the problem with asbestos was the very high aspect ratio and (obviously) bio-incompatibility.
Black Silicon spikes don't have anywhere near this kind of aspect ratio and are comparatively biocompatible.
Source: doing a silicon surface science nanotechnology masters.
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Source: doing a silicon surface science nanotechnology masters.
Grateful for some links on the stability of the spikes with temperature.
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Given their ability to kill bacteria, I have to wonder whether what you're saying about the silicon is true.
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In addition, the asbestos crystal lattices tend to fracture linearly, which results in them remaining in the organism causing damage for a lot longer.
Useless against biofilms (Score:5, Informative)
Except this only works on the bacteria on contact.
Get a bit of slime and the surface never touches most of the bacteria.
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Except this only works on the bacteria on contact.
Get a bit of slime and the surface never touches most of the bacteria.
Most of the biofilms are... guess what... bacteria. The smoothness of the surface may even promote the formation of a bacteria nanofilm.
Citation [swinburne.edu.au] at about 4:12 (warning: mp4 - aprox 17 minutes).
At about 10 mins: some models of cycada wings surface; most interesting: starting about 11 mins, SEM imaging showing "impaled" bacteria, the "impaling" process (takes about 4 mins in real life)
.
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But if the surface kills the bacteria when it first lands, then there's nothing to put down the slime in the first place.
It's a chicken and egg problem with the egg already present. We already have many bacteria ready to die on whatever adverse surfaces are out there and we won't run out.
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Except this only works on the bacteria on contact. Get a bit of slime and the surface never touches most of the bacteria.
Is there anything that biofilms don't regard with contempt? Short of sustained incineration and (maybe) a switch to all-fluorine atmosphere, those suckers seem to be nigh-unstoppable.
Heard it all before (Score:5, Funny)
"It slices!, it dices! and chops and grinds for all your bacteria processing needs! No more fuss and muss! No more missing mitochondria! And all this can be yours for 4 low monthly payments of just $39.99! It's a limited offer, so get yours nooowwww!"
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Me too...
Probably because I'm not American, and thus didn't grow up with Mays infomercials.
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Note, should be "limited time" offer. Now you know why I'm not in marketing.
Pretty cool. (Score:2, Interesting)
Can this structure of silicon also be used for other things?
Such as battery anode? Massive surface area would be highly useful.
Inside solid caps? Letting us shrink caps even smaller and still keep the same values.
How about solar cells? Something that provides very low light back is absorbing all it can. And massive surface area would be useful.
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Clarification after rereading TFS (Score:2)
Nosocomial Implications? (Score:2)
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Well quite. The victorians used them everywhere in hospitals and so -unwittingly - created places that were for the time pretty damn clean. But then a plain old metal isn't hi-tech and 21st century gee-wiz so regardless of being cheap and effective its unlikely to be trumpeted by the kool kids and researchers with an eye on the next grant payment.
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