Forgot your password?
typodupeerror
Science Technology

Black Silicon Slices and Dices Bacteria 78

Posted by samzenpus
from the cut-them-up dept.
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."
This discussion has been archived. No new comments can be posted.

Black Silicon Slices and Dices Bacteria

Comments Filter:
  • Durability? (Score:5, Interesting)

    by fuzzyfuzzyfungus (1223518) on Thursday November 28, 2013 @09:43PM (#45552313) Journal
    Does this stuff have any sort of neat catalytic effects or other cleaning mechanisms, or are the structures so tiny that bacterial polysaccharide goop won't neutralize them inside a week?
    • by Taco Cowboy (5327) on Thursday November 28, 2013 @09:52PM (#45552347) Journal

      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 ?

      • by eyenot (102141) <eyenot@hotmail.com> on Thursday November 28, 2013 @09:57PM (#45552365) Homepage

        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.

      • by fuzzyfuzzyfungus (1223518) on Thursday November 28, 2013 @11:37PM (#45552675) Journal
        If nothing else, attempting to answer that question will probably make computational fluid dynamics types cry bitter tears of computational inadequacy...

        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...
        • by Charliemopps (1157495) on Friday November 29, 2013 @01:10AM (#45552997)

          I was going to mod you up, but they don't have an option for "You just made my head assplode"

          • by fuzzyfuzzyfungus (1223518) on Friday November 29, 2013 @03:53AM (#45553385) Journal
            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...

            (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.)
            • by srussia (884021) on Friday November 29, 2013 @05:48AM (#45553851)

              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...

              • Well, that doesn't tell us anything about bugs; but if you've got a proposal that will make wings work in a vacuum with just a tweak to surface geometry... I think we can overlook the bug issue and examine that result.
                • Whew! If guys like you gravitated to automotive development I would have my Camaro Jorge Jetson by now.
            • by ihtoit (3393327)

              one word:

              Bumblebees.

              That is all.

            • by kermidge (2221646)

              "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,

              • My suspicion is that you'd need pretty alarming (by biological standards) voltages to get significant changes in the behavior of oxygen and nitrogen; and (for some vexing reason having to do with 'practicality' or such nonsense) my shoddy attempt at research was drowned out by the wealth of sources addressing the behaviors of dielectric gasses from the perspective of somebody who wants to fill his high-voltage transformer with one, so I couldn't find anything about viscosity, adsorption, etc.

                That said, w
                • 1 volt differential across 250 nano metres is a very high gradient in volts per metre... 4,000,000 V/m
                • by kermidge (2221646)

                  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

      • by jafiwam (310805)

        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

      • by Optali (809880)

        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

    • by Animats (122034) on Thursday November 28, 2013 @11:52PM (#45552719) Homepage

      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.

      • by fuzzyfuzzyfungus (1223518) on Thursday November 28, 2013 @11:58PM (#45552745) Journal
        I imagine that that's why those bugs are getting away with them. Nothing like being biological to get aggressive self-repair capabilities thrown in more or less for free... Pending nanites, no such luck on our end.

        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...)
        • by TubeSteak (669689)

          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.

        • Was reading about that the other day, the nano-spikes act to break up water droplets into smaller droplets allowing them to bounce off the surface more easily. The same principle also allows the droplets to slide off the surface more easily, useful for boats and planes. Shark skin has similar nano-scale surface geometry, allowing the shark to move faster with less energy. With dragonflies it's apparently the network of ultra-fine capillaries on the wings that does the same job as the spikes.

          As you say if
        • by martas (1439879)
          Plus, bugs don't live very long. If you only need your ship to work for a couple of weeks, there's a lot you can get away with too.
      • by Anonymous Coward

        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.

  • Can I get this for my car, to absorb radar and lidar?

    • Re:Radar (Score:5, Informative)

      by c0lo (1497653) on Thursday November 28, 2013 @10:32PM (#45552473)
      Two processes are known (so far) for the production of black silicon [wikipedia.org]: pick one.

      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]

    • by femtobyte (710429)

      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)

        by FatdogHaiku (978357) on Thursday November 28, 2013 @11:20PM (#45552637)
        Happily, I read down the thread this far instead of rushing out to get a few square meters of double sided tape and a half a million dragonfly wings... thanks for saving my time and I'm pretty sure all the dragonflies that won't have to walk home would also be appreciative.
      • "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.

  • by ffflala (793437) on Thursday November 28, 2013 @09:48PM (#45552329)

    "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.

    • by femtobyte (710429) on Thursday November 28, 2013 @09:52PM (#45552345)

      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.

      • by ffflala (793437)
        Good point, skin would have massive peaks and valleys to scale. Perhaps a fluid medium then, streamed over a sufficiently long, inclined surface.
        • What you are describing sounds like a waterslide. ;)

          • by femtobyte (710429)

            A long waterslide flowing with an abrasive grit slurry, however, might not be the most fun kind of waterslide.

      • 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)

    by Anonymous Coward

    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)

      by Anonymous Coward on Thursday November 28, 2013 @10:02PM (#45552387)

      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.

      • by c0lo (1497653)

        Source: doing a silicon surface science nanotechnology masters.

        Grateful for some links on the stability of the spikes with temperature.

      • by Shavano (2541114)

        Given their ability to kill bacteria, I have to wonder whether what you're saying about the silicon is true.

      • In addition, the asbestos crystal lattices tend to fracture linearly, which results in them remaining in the organism causing damage for a lot longer.

  • by nuggz (69912) on Thursday November 28, 2013 @10:06PM (#45552409) Homepage

    Except this only works on the bacteria on contact.
    Get a bit of slime and the surface never touches most of the bacteria.

    • by c0lo (1497653)

      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)

      .

    • But if the surface kills the bacteria when it first lands, then there's nothing to put down the slime in the first place. Biofilms arise with the bacteria, not before.
      • But can the debris from the killed bacteria build up and form a layer of detritus?
      • by khallow (566160)

        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.

    • 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.

  • by Tablizer (95088) on Thursday November 28, 2013 @10:14PM (#45552431) Homepage Journal

    "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!"

  • Pretty cool. (Score:2, Interesting)

    by Anonymous Coward

    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.

    • High efficiency solar cells and ultra-sensitive sensors are among black silicon's main uses, unfortunately it appears the material is too expensive for everyday commercial use. - WP is your friend.
  • This sounds like some cutting edge (bon mot premeditated) technology, but I swear my brain saw Blacon Slices on the first skim.
  • It would be interesting to see how this measures up with the bacteriostatic characteristics of copper and brass.
    • by Viol8 (599362)

      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.

      • Fortuitous happenstance... I see no more viable conclusion to draw than copper's early availability (literally right after sticks and stones) to my grandcesters for tool and weapon production.

One small step for man, one giant stumble for mankind.

Working...