SPNs Might Change the World, So What Are They?

Slow it down, Hank

I worked with a type of hydrogel in my one summer of actual benchtop research at Miami University twenty-some years ago, and I certainly never would have imagined them to have the properties described in today's video. I was just looking at the ability of the get to absorb and subsequently release transition metal ions, so I wasn't exploring their mechanical properties, admittedly.

SPNs, in case you were wondering, are supramolecular polymer networks, networks of polymer chains held together by - according to this video - non-covalent bonds like intermolecular forces like hydrogen bonds.

Halfway through the video, Hank makes a turn to a possible application of a particular SPN that was used to help paralyzed rats to regrow nerve cells and allow them to 'walk' again. That's a long way from human trials, but the initial study sounds amazingly promising.

5 Ways Biology Is Transforming Buildings

Evolution has reached some pretty outstanding solutions to environmental challenges. It's sort of the ultimate in the fail fast philosophy of engineering. Every mutation is an iteration, and natural selection easily sorts out which designs to pursue. And natural selection has come up with some pretty ingenious solutions.

This video goes through five of those natural solutions and how material scientists are trying to mimic those solutions.

• "Sweat gland cement" - looks at cement blends that contain reinforcing fibers and APP-PER-EN. As the temperature of the modified cement rises, the fibers melt (absorbing energy) then the APP-PER-EN foams and releases gasses to put out fires. Weirdly I can't find anything on the web searching for that APP-PER-EN and cement. I'd appreciate a link to more info if anybody can find it.
• "Polar bear heating" - considers the white fur/black skin combination of polar bear coats. The black skin absorbs heat allowing them to maximize the absorption of heat energy, even leaving them invisible to infrared cameras. German scientists are using a similar idea to adjust the thermal absorption of heat energy for passive solar heating.
• "Homeostasis facades" - are based around muscle fibers expand and contract to regulate heat in the muscles. The facades would be two layers of glass with polymer between them that would expand - blocking sunlight - as they heat up and contract - allowing more sunlight in - as they cool.
• "Mantis shrimp cement" - sees Purdue scientists studying mantis shrimp claw material with its linear structure formed in spiral layers that work as crack arresters. The scientists used a 3d printed concrete structure and printed the layers in spirals similar to the mantis shrimp claw material.
• "Fish scale glass" - takes a look at laminated glass being made more similarly to how fish scales overlap each others. They etched two layers of laminated glass and laminated them together with the diagonal layers flipped to create a diamond-like pattern that makes the glass much stronger than leaving the etchings in the same direction.

Scientists made LEDs 60% brighter by copying firefly lanterns

Source - https://www.pnas.org/content/109/46/18674

I fully recognize that the above image is a bit detailed. I'd rather embed the video I think is here, about halfway down the page. It worked when I first viewed the article a few months ago, but by the time I got around to posting, the video seems to have died.

Such is life, eh?

Speaking of 'such is life', the article today - written for popular consumption from Gizmodo or the original research from Proceedings of the National Academy of Sciences or even a middle ground from phys.org- shows a great example of biomimcry. A team of Korean scientists wondered why firefly bulbs were so bright, so they headed to the electron microscope to check out the structures of the light-producing organs.

Turns out the organs were shingled, allowing light to transmit from the top and also the edge of the surface. When the scientists mimicked the structure, their LED was 60% brighter than an equivalent using an unshingled structure.

Technically, "[t]he bioinspired OLEDs clearly showed side-enhanced super-Lambertian emission with a wide-viewing angle" (from acs.org).

I would've said that first, but it's such a simple sentence, I wasn't sure you'd read onward if I opened with that.

Material Uses Insect Technology to Stay Dry Under Water

Let's start with the basics, shall we?

In general water is bad for the long-term durability of most surfaces - especially metal surfaces.

Water molecules hold together pretty well. I've even seen (and highly endorse) magnets that show this.

Water molecules have some volume, especially when they hold to other water molecules.

(Now, the tougher step...)

If you can make bumps...pores...posts...something on the surface of a material that leaves spaces too small for water drops (clumps of water molecules) to go into, the surface of the material will stay dry.

Seriously...like forever dry...not from a coating that will eventually wear off...permanently dry (or at least for four months as the early research shows)...

Left column: (top) Polymer/HFS (NC1) composite coating on aluminum substrate, (bottom) silicon square microposts. Middle column: (top) zinc oxide nanorods on silicon substrate, (bottom) silicon nanowire forest. Right column: (top) silicon microgrooves, (bottom) silicon nanograss.

See those scanning electron micrographs (SEM) above? They're from an article on Nature's website. Each surface was tested to see how long it would resist being wetted when immersed in water (then in water that had been thoroughly degassed - to make sure it wasn't gas bubbles being trapped that resulted in the lack of wetting).

Left: Wetted surface with 25 μm pillar spacing. Middle: Wetted surface with 5 μm pillar spacing. Right: Dry surface with sub-micron pillar spacing. Abbreviations: Frozen water (H₂O), Silicon substrate (Si)

And there you can see their results. Make the pillars wide enough to leave 25 microns of space, get a wet surface...5 microns, still wet...less than one micron, dry...forever dry...perfectly dry.

There's a nice summary of the article on IFLScience's website, but you do, as always, run into the issue of that F in the web address...

Superfast clotting agent could save many lives

I have to admit that I found this story from the not-school-appropriately-named I F*&(ing Love Science website. It's honestly way more entertaining and informative than I want it to be because I can't ever share these links on my class Facebook page - which I hate.

That's I hate not being able to share the links.

Not that I hate my class Facebook page. I don't. I actually like it a fair bit.

The video shows an in-development product designed to clot blood nearly instantly. It's apparently a polymer made of plant-derived polymers extracted from plant cell walls - like Lego blocks according to the company's co-founder and CEO.

Xylem from plants can be used to filter water

Sometimes mother nature does it best.

The need for clean, cheap, disease-free drinking water is one of the greatest health needs in the world. Scientists have tried all sorts of materials but invariably run into issues with cost, durability, availability, scaleability, or something along those lines. This article reports on research into using xylem from coniferous trees was able to remove 99.9% of bacteria in samples of water.

It's not an area that we usually discuss in materials science because we're not necessarily building anything from the xylem, but being able to take advantage of a natural material's natural properties is every bit as important as being able to adapt that material for our use.

Mechanical Engineers Discovered How the Arapaima Becomes Piranha-Proof

A recent article in Advanced Engineering Materials that has been reported all over the place on the web looked at the scales of Arapaima gigas, a freshwater fish that lives in the Amazon River and is able to successfully defend itself from the bite of the piranha.

Researchers found that the scales of the arapaima are brilliantly constructed with an incredibly hard, outer and inner, mineralized layers sandwiched around much more flexible, collagen fibers stacked in opposite directions providing a marvelous flexibility.

The video above mentions (at about 0:38) the possibility of extending this concept to produce flexible ceramic materials.

Nature, man, she continues to reveal amazing secrets.

Here are four different reports on the research though the original article is thankfully not behind a subscription wall:

• Jacobs School (where the research is being conducted)
• livescience.com
• sciencemag.org
• neatorama.com

How honeycombs can build themselves

Image source - http://www.huffingtonpost.com/2013/07/17/honeycombs-build-themselves-physics-bees_n_3611825.html

A recent article in the Journal of the Royal Society Interface explored the physical reasons behind the creation of the classic beehive hexagons, whether they were intentionally created by the bees to be hexagons or whether the hexagons arose naturally from the physical forces at work within the beehive.

Apparently in this case physics beats biology...

Karihaloo and his colleagues seem to have clinched this argument with their study. The team interrupted honeybees making a comb by smoking them out of the hive, and found that the most recently built cells have a circular shape, whereas those just a little older have developed into hexagons. The authors say that the worker bees that make the comb knead and heat the wax with their bodies until it reaches about 45 ^oC — warm enough to flow like a viscous liquid.

Stupid physics...

Surgery without stitches

Again scientists look to the natural world for an ideal material, this time looking at crabs to mimic the chitin attachment between the crab's shell and underlying musculature. This material - surgilux - is a "thin polymer film based on chitin" that 'melds' to the flesh when heated via infrared light.

According to Dr John Foster in the video, the melding is simple, cost-effective, anti-microbial, non-scarring, and non-dependent on the surgeon's skill level.

Silk - If spiders and worms can do it, why can't we?

Biomimetics is a fascinating field in which scientists take inspiration from the natural world to improve out technologies. Here a video from the National Science Foundation looks at one of the major struggles that scientists are trying to overcome in making artificial spider silk - particularly at the difficulty in storing liquid spider silk until it is solidified after it comes through the spinnerets.