New material that can absorb and release enormous amounts of energy | Hacker News Reader

New material that can absorb and release enormous amounts of energy

phys.org

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I was hoping it would be called Astrophage...

ref: https://en.wikipedia.org/wiki/Project_Hail_Mary

I was hoping for Vibranium :)

This is also the first thing I thought of when reading the title.

Did you get to the horrible destruction and millions of people dying part?

Not that astrophage wouldn't be cool!

I actually wish the book had been more about it… the post launch part of that book was honestly the least interesting writing I’ve ever read from Andy Weir.

I also still can’t get over using a hand cranked winch instead of using the entire ship as a capstan while performing a barbecue roll. (Hopefully that a winch is involved is not too much of a spoiler for anyone)

I agree! The whole progress of what must have happened as the world is pushed into "dark" ages. There is a book in there!

btw. I'd recommend all the Expanse books if you're interested in how the whole civilisation manages a catastrophe.

Source pub, with some videos of the loading response:

https://www.pnas.org/content/119/1/e2118161119

This is the comment referencing flubber that you're looking for. Flubber!

Exactly why I came to the comments. Tbh, the "idea" of flubber is pretty futuristic. Imagine shoes that can bounce/return your running impact which could improve your speed by some real significant factor.

I mean, springs would do that. Maybe a latch with slightly delayed release mechanism would work better to time the energy release for optimal running. But unless you want to violate conservation of energy (like flubber presumably does) then springs would get you there.

There are, in fact, such shoes, and they do provide what has been called an unfair advantage in track sports.

That is actually already a thing, and yes they do provide a significant advantage.

Other people point out shoes, but there's also these contraptions that are basically springs / elastics inspired by kangaroos; I had to google a few times, but their common name seems to be "jumping stilts" [1]. There's also more compact variants, jumping boots, that look like leaf springs underneath skeeler / ice skating boots [2]

[1] (no affiliation) https://www.amazon.com/Air-Trekkers-Exercise-Entertainment-P...

[2] https://www.amazon.com/Jumping-Shoes/s?k=Jumping+Shoes

The actual paper: https://www.pnas.org/content/119/1/e2118161119

Intersting material.

More interesting to me is the Army being willing to sponsor research simultaneously with a Chinese institution...

Often it is done simply to get reports. The research is likely going to happen anyway in a lot of these areas. Signing a deal to give some money commits the researchers to give reports used to monitor the program.

I was surprised to see that, too. It is a rare combination, perhaps a hopeful one if there are problems that funding agencies in both countries see as important-enough to fund alongside their frequently-presumed competitor.

However, a closer read suggests that the author did the work at UMass Amherst, then took a professorship in Shenzhen.

at Harbin not Shenzhen

It's the Shenzhen campus of HIT.

Interestingly, in 2018 Wuhan lab applied for US DARPA grant to produce a bat coronavirus chimera.

https://www.newsweek.com/darpa-denies-funding-defuse-wuhan-i...

https://theintercept.com/2021/09/23/coronavirus-research-gra...

Not quite the same, but got me thinking: Could we theoretically power and refuel car in the following way:

- Take a cube of X elastic material and squish it really dense with a big machine.

- Power the car via the pressure of the material trying to expand.

- Once it's nearly depleted (fully expanded), take it to another squishing station.

I imagine you couldn't store anywhere near enough power that way today, but then that's also the kind of problem the linked material is trying to solve, right?

https://en.wikipedia.org/wiki/Compressed_air_car

Compressed air energy storage is already a thing!

The energy stored is limited by the tensile strength of the container. The best capacity for a unit weight is from laminated carbon fibre tanks, but this still doesn’t even approach the energy density of ordinary hydrocarbon fuels.

You’ll find that there’s lots of interesting ways to store energy — like flywheels or chemical cells — but one way or another they’re all inherently limited by chemical bond strengths.

Fundamentally all energy storage is some sort of stored “tension” in chemical bonds that can be released to do useful work.

The reason fuels are so good is that this release needs a second component (oxygen) that is kept separated. This makes high energy densities safe.

No separation — like with compressed gas — means that the energy storage is a bomb waiting to go off. It would be too dangerous to use.

Thanks, yeah that makes complete sense. Plus I would imagine the more energy density you need, the heavier your enclosure has to be, always partially negating the benefit!

Precisely. Any attempt to "optimise" the specific energy of a storage approach will inevitably bring it closer to closer to the point where it explosively disintegrates.

This is why it's a bit hilarious to see how upset people are about lithium batteries occasionally exploding. That's... sort of the point! They've been optimised until the safety margin (=weight) is a low as possible. You want safe batteries? Carry around something the size and weight of a brick!

Ditto with all possible kinetic energy recovery system (KERS) designs. You can have weight-efficient or safe, but not both.

Lithium batteries typically explode because the electrolytes we use are highly flammable. It's actually entirely incidental to the amount of energy stored in the battery. A Li-ion battery with a different electrolyte material could have the same energy density, but a greatly reduced risk of fires and explosion.

Only somewhat - batteries tend to explode when damaged (punctured, squished, etc) when they short internally, or when they get a thermal runaway.

Putting armor, heat sinks, etc. on them does make them safer. Adding battery safety circuitry (charge control, overcurrent protection) also helps. It also adds weight. Unarmored lipo batteries are notoriously dangerous for a reason, and it’s not the electrolyte.

Compressed gas is not too dangerous to use. It is an energy density problem. There are prototype vehicles that fill the same niche as current EVs.

Failure rates for automotive Li batteries are quite low. In the range of 0.001 per 100K vehicles.

I'm aware, and compressed gas storage containers are equally low if not lower. They also fail in a way that is safer than batteries fail. The tanks are engineered to split and the limited, usually zero, shrapnel is redirected downward.

What really limits compressed air as a vehicle energy store is the inability to reasonably run climate control off of it.

And the incredibly low round trip efficiency - heat production then loss to the environment as part of compression is pretty brutal on that front.

Excellent analysis, thank you, but this line is a little strange:

> The reason fuels are so good is that this release needs a second component (oxygen) that is kept separated. This makes high energy densities safe.

Don't fuel tanks (for internal combustion engines, for example) typically also contain oxygen? You make it sound like a full tank is safer than a half-empty tank.

I assume you're actually saying that for safety we want the reactants to be stable at common atmospheric temperatures and pressures, and we don't want reactants that spontaneously combust on contact with air or common materials (including each other).

They don't contain nearly enough oxygen to liberate all the stored energy.

Also, especially since gas tanks are no longer directly open to the atmosphere, I wouldn't be surprised if the oxygen concentration was too low most of the time for combustion to be possible.

In principle we could calculate the weight of oxygen in half a fuel tank's worth of air, and work out how much energy that would release if it was used in combustion with the fuel there.

In practice, though, you're right, that we'd have to think about the oxygen concentration, which would immediately start dropping as the fuel burned. Also, it's not easy to calculate what temperature the tank would reach, and for how long, and whether that would cause it to rupture.

For reference, though, the testing process for fuel tanks can include: "the tank being exposed to a pan of raging petroleum coming through specifically designed firebricks to intensify the effect of the naked flame. The tank has to be capable of securely containing diesel during the test for 90 seconds."

https://corillaplastics.co.uk/rotationally-moulded-diesel-fu...

  > You make it sound like a full tank is safer than a half-empty tank.

Back when I was working as a Ford tech, I was told that a full tank is a fire hazard. An empty tank is an explosion hazard.

You can run away from a fire. If the fuel pump can be changed without dropping the tank (e.g. by going under the rear seat or truck bed), then it is preferable to work on a full tank.

A full tank is safer than an almost empty tank.. Also the tank is designed to keep the vapor part of the gasoline too saturated to explode, this is why there is a latch on the fill tube. I found this Quora post: https://www.quora.com/How-come-the-gasoline-in-gas-tanks-nev...

And even if it can explode in the situation where there's almost no fuel left, in that case it's not as bad as liberating the full energy of a full tank, which is what you'd do if you have a flywheel spinning with the same total energy as a full tank of gasoline. That would be madness.

Heh I came to think of the recent demo of the company that wants to spin up satellites on earth and THROW them into orbit. If something goes wrong in that spin-up, they would destroy the entire launch facility and whatever is in the way.

https://youtu.be/JAczd3mt3X0

I once had a CDROM open while the CD was spinning at like 40x or so, it ejected and went into the plaster wall. And that was just a CD..

You may think of it as one key for all energy boxes (a broken valve or a hole in a gas tank) vs multiple keys for every energy box (oxygen molecules). To burn a liter gasoline you have to mix it with the ~same amount of oxygen. It never explodes all at once except in that rare situation. An empty tank is exactly that, because gasoline is volatile.

Energy boxes that can be opened with a single key are more dangerous, cause more prone to accidents. Pressure, kinetic storages, self-sufficient explosives are all much more dangerous than stable chemical bonds.

Also, gravitational potential can be accumulated in a single-key way too. That’s why cliffs are dangerous, but staircases are less so, because energy release is dosed with each step and flight. You have to actively err on stairs to take fatal damage.

There are various forms of energy and various forms of energy storage, including chemical energy and gravitational potential energy.

We probably think of energy as entropy like gases because e.g Maxwell?

Examples of gravitational potential energy:

- A water tower or a pulley with weight suspended a greater distance from the most local mass/graviton centroid.

Potential energy: https://en.wikipedia.org/wiki/Potential_energy

You can, but the energy efficiency of this would be horrible. You'd lose a ton of energy to waste heat. Trying to collect that waste heat and turn it into useful energy would have a horrible Carnot efficiency.

You keep it in an insulated container. Or, you let the environment warm it back to room temperature as it expands.

Clock spring?

Just to be clear: This appears to be mechanical storage (i.e. Hooke's Law) rather than electrical storage. They're embedding magnets into elastomers to create a programable "metamaterial" that has controlled non-linearities in elastic response.

I mean, to be pendantic, mechanical storage actually is electrical storage, just not electrochemical storage :-P

I find this comment repulsive

elaborate?

he's trying to be punny.

are you positive?

I find this comment attractive.

I'm surprised they call it a metamaterial when the features are on the order of millimeters.

I'd argue that some of the most interesting metamaterials are macroscale. Like radio telescope arrays or the dimples on a golf-ball.

The length scale of a metamaterials' features should be complementary to the length scale the metamaterial is acting on.

Kind of squirrely, and I tried really hard to phrase that so it isn't a tautology. But if you're dealing with radio waves, your metamaterial can have huge (meter-scale) features. If you're dealing with visible light, your feature size is on the hundreds of nanometer scale.

Thin films have a characteristic bending length: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.11..., and this determines the size of features you should pattern to exploit that bending/folding interaction.

That makes sense. Thanks for the explanation.

I think in mechanical metamaterials the characteristic length defining the "metamaterial region" is rather the wavelength of pressure waves in the material you're considering - much like in electromagnetics you want the patterning (cell) length to be much less than the wavelength of radiation. In work like this they are effectively looking at 0.1 Hz or lower - near static loading - so I think pattern size can be quite large (around 600 m wavelength in bulk rubber for 0.1 Hz). This interpretation also replicates the localized behavior in the shock experiment videos. When the platform is dropped an impulse is applied with frequencies above the metamaterial regime for the material, so you see highly asymmetric response through the material - implying that the macroscopic "metamaterial" property characterization is insufficient to predict response, and so analysis must be done at feature scales rather than wavelength scales. The idea being that a "metamaterial" is a structure that can be treated as a bulk continuous material with a particular defined response as long as the interacting frequencies are all sufficiently low (far below the characteristic wavelength of the material).

I think the bending analysis you cite can determine the relative feature sizes desirable for certain "micro-scale" mechanical behavior, but it's possible to build a mechanical "metamaterial" much larger than that as well.

No numbers whatsoever. Kind of a useless article

Joules per Kg or gtfo.

Well not just energy capacity [J/kg = m^2/s^2 = 1/3600 W hr/kg], but power capacity [W/kg = J/(kg s) = m^2/s^3] too.

Replace the permanent magnets with coils and you get the fabric/stuff from the batman movie (memory cloth?)

It would be great if this material could help with brain damage in contact sports by making helmets better.

That's a very specific application.

Isn't there a bound on the efficacy of a helmet based on its size / thickness? I.e. your head's initial velocity and the thickness of the helmet constrain the distance over which your head's velocity must drop to zero, so there's some minimum force that must be applied to your head no matter what the helmet's material is?

Conclusion: The helmets must be bigger, much bigger.

I don't know their current thickness; maybe 2 cm? If we expand that to a cushioned 10-20cm all the way around their head, the force would be reduced by a factor of five to ten. I'd imagine they could head-butt all day long without damage, and football games would be much more entertaining.

Helmets have an interesting correlation with concussion. They can help a lot in cycling, hurling, and f1, but can encourage reckless collision seeking in american football for example. Contact sports are intrinsically dangerous and introducing protection from one type of damage can allow increase in other damage forms.

Avoid collisions

I reckon rugby must change the most, which is a real shame because rugby at the highest level is amazing

Though ice hockey is pretty daft

There is a strong correlation between neck weakness and brain damage in contact sports

Search "NFL neck" in a search engine and look at the images

Apparently people have been experimenting with magnets in football helmets for several years now, albeit much larger ones: https://leaps.org/this-brain-doc-has-a-repulsive-idea-to-mak...

> This research, which was supported by the U.S. Army Research Laboratory and the U.S. Army Research Office as well as Harbin Institute of Technology, Shenzhen (HITSZ)...

I didn't expect that!

Anyone know of a metamaterial actually being used in the real world?

https://us.kef.com/metamaterial

Can it be used for batteries ? I know large scale mechanical batteries are a very efficient way of storing energy, but no idea about the state of small scale ones.

Without reference, it's hard to know exactly what you mean with large scale vs small scale, but I do know a person who has a pool of water high up on their property, which they let run to the bottom pool when they want cheap energy when prices are high and pump it up again when prices are cheap but they have no need for it currently. I'd say that's relatively small scale.

Bigger scale: https://en.m.wikipedia.org/wiki/Helms_Pumped_Storage_Plant

That's a good energy storage mechanism, but do you know what the efficiency is? Also, how much energy could you practically store there?

Can't speak to efficiency, and obviously depends a lot on assumptions... but a big pool with a 40 m height difference stores about a gigajoule [1].

[1] https://www.wolframalpha.com/input?i=volume+of+an+olympic+sw...

Hmm, 278 kWh, that's great for a house, though you need a fairly tall and big water tower for that.

Personally, I want a wind-up EV! ;-)

How would it's usable energy density compare to, say, a Lithium Ion battery (or some other thing I'd be familiar with)?

Very low, or they'd mention it

Reading the paper my first thought was, could this be scaled up for a a tactile touch screen display?

the pdf of the actual paper: https://www.pnas.org/content/pnas/119/1/e2118161119.full.pdf

Can this be made into bulletproof clothing that looks like normal clothes? That would be cool

UHMWPE already can do that.

Ahh, but can it be made cheap enough to displace the Superball?

Who's going to be the first to make a slingshot from this? :)

Can it be used for shock absorbers or seat belts?

It's funded by the US army. They clearly want a material they can coat their tanks, etc with to defend against anti-tank missiles.

Is an alloy a metamaterial?

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