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The Orange Goo That Could Save Your Laptop
Barence writes "A British company has patented what can only be described as an orange goo that could save your laptop or iPod after a nasty fall. The amazing material is soft and malleable like putty, but the substance becomes solid instantly after impact. You can punch your fist into a ball of the material sitting on a desk and not feel a thing, according to the staff at PC Pro who have been testing the material, called 3do. It's being used by the military, the US downhill ski team, and motorcycle clothing manufacturers to provide impact protection in the event of a crash. However, it's also appearing in protective cases for laptops and MP3 players."
Impact resistance is complicated, but there's parts that are very, very simple. Let's say you drop your laptop from five feet up. When it hits the ground, it'll be going at a certain velocity (I am currently too lazy to calculate it) with a certain amount of momentum. That velocity and momentum will go into crushing the impact point against the ground. If the impact point is forced to decelerate rapidly, and is a small enough point, it'll be subject to a huge amount of force. Boom, shattered plastic.
Now we add padding. The thing about padding is that it doesn't actually reduce the velocity or momentum in any way (in fact, unless it's literally weightless, it *increases* momentum.) It also doesn't change the basic physical requirements - that momentum will get absorbed somewhere. Guaranteed.
There's two ways the padding helps. First, it lets your dropped object decelerate more slowly - instead of having to go from fall to stop in a tiny distance (namely, the amount your laptop plastic deforms without permanent damage) it goes from fall to stop in a much larger distance - the distance that the padding can be compressed. (Plus the plastic deformation.)
Second, it provides - potentially - a larger impact zone, distributing the force more equally over the plastic of the laptop. A force that would shatter a corner may not do much at all distributed over a few square inches.
The first part, unfortunately, has some very basic physical limits. If the padding is an eighth of an inch thick, it will provide, at most, an eighth of an inch of extra speed reduction. There is just no way to improve this until you fit your shock absorber with little rockets and sensors to determine when it's about to impact the ground.
The second part is a lot more theoretically capable, but also a whole lot harder to solve. The ideal situation is a material that somehow deforms at the impact spot in exactly the manner that lets it stop at its maximum deformation point, without any extra jerks or impacts, while simultaneously spreading the impact over the entire surface of the protected item.
That is a damn hard thing to accomplish. If he's succeeded in it, or in anything remotely like it, I'm impressed.
The press releases seem to feel that d3o is absolutely fantastic for human garments, where the fabric has to be malleable until the impact occurs. That's quite different from electronics protection, where malleability is simply not an issue, and I'm not convinced that it will make the changeover smoothly.
We'll see.
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I guess there's a limit to the amount of shock it can absorb. I would imagine its properties have been tweaked so that it stops any impact within its own thickness. Obviously if the impacting object is travelling faster, that results in more rapid deceleration and thus more forces transferred to the delicate internally-bits of your laptop. For dropping off a table though, it probably provides the smallest possible deceleration force against the floor, compared to protection materials currently on the market.
My suspicion would be that rather than rather than causing the linear deceleration of a simple spring constant, (like most other foams, rubbers, etc.), it provides an exponential deceleration: the stopping force in a shear-thickening fluid is proportional to the speed rather than the displacement. This means that the material starts acting from the very moment of impact, as that is the point with the highest speed. A spring, (or foam, or rubber, or anything else that acts like a spring), would do essentially nothing until the impact has squeezed it enough to get a decent counter-force out of it. But by that time it might be too late, and the spring might have already bottomed out. I'd be interested to see some numbers for this gel, to back up the stuff I've just written!
/Disclaimer: Mechanical engineering undergraduate. Don't have my qualification yet; take above post with a pinch of salt.
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My professor in engineering mechanics showed me a sample of a material with very similar color and characteristics sometime around october '08. Now I know, where I can get a sample for goofing around ;)
However, this won't protect your precious harddisk. It works very well for protecting humans, mainly because it adapts to the form of the pressing surfaces (aka your head and a wall) and then distributes the pressure over a bigger area. It does almost nothing though for the rate of deceleration - face it, your notebook, falling from the table goes from v^2=2*g*s (s= table height, let's say 0.8m)=4m/s to zero in about - well, let's say 1mm as this stuff gets rigid very quickly. This makes it face a deceleration of 8000g. Hell, let's say 5mm and it's still 1600g. Nope, this won't save your harddisk as they're rated for 300 to 500g in every direction and a lot less when active. Thinking about it, it seems like a good idea for the notebook to come apart on impact, as this might give your harddisk another few millimeters for controlled deceleration and thus keep it withing mechanical specs.
In other words: Yes, the surface of your precious Macbook will be scratchfree after the fall, the harddisk will still be toast.
Heh, glad I put that disclaimer there. Stopping force is proportional to velocity, (technically shear rate), in a Newtonian fluid such as water or oil: in a shear-thickening fluid viscosity is proportional to velocity. Viscosity is the proportionality constant linking speed and stopping force, so I guess that makes stopping force proportional to the square of the speed.
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