artificial liquid idea needs help and scrutiny

[quarky]

This is another idea I'd like to clean out of my closet:

Small glass spheres are sometimes used in chemistry; they flow almost like a liquid. They would be very comfortable to lay on, if you didn't inhale them.

Make them slightly larger, with a specific gravity similar to a human body, and you're almost floating.

Make a mix of the glass spheres; some smaller and denser, to form a bed on the bottom; some larger and somewhat denser than water; and a top layer, of larger, lighter balls. This would be the blanket.

Perhaps enough air remains between the balls to approximate breathing under water. The space would be at least 27%; probably more that 33%.

For what purpose?

A hot tub that could be rinsed cheaply? (The box of balls would have a screened bottom, with a drain pan)

Sensory deprevation tank that negates the need to float on top of water?
(fans beneath the tank of balls would ensure fresh air exchange)

Maybe. But I'm seeing this idea as having value in treating burn victims.
And possibly as a crib for infants. Wash the pee down; no diapers. No sids.
(Yes, provisions would be needed to prevent choking on the spheres; perhaps a head stocking of mesh.)

How nutty is this?

[sanguine]

I've worked a lot with glass beads in the ballpark of 0.5 mm (half a millimeter) across, and they frequently exhibit annoying, static-charge-related behaviors -- that is, they stick to everything. Although I think the "bead bed" idea is pretty nifty, I believe you'd have practical issues because of adherence for one reason or another (static aside, people are also inherently sticky, and you don't want a doctor having to pull beads out of scar tissue on a patient).

Cool idea in principle, but I think it would have some downsides.

[Rocko]

I remember my dad telling me about something similar - large "bean bags" with air being forced through the beans to achieve that sort of effect. As you say, they were used to provide a comfortable a bed as possible for burns victims.

He was telling me about this when I got a beanbag for my birthday, so this must be about *cough cough* 30 years ago I guess? I've never heard of anything similar since though, so maybe it was just being trialled?

[Reality Check]

There are already "bead beds" in existence (mostly for hospital use), e.g. google "Beaufort Bead Bed system".
There is a good description of one system used to treat burn victims here.

[OnlyTellsTruths]

I seem to remember this from another post in another thread. Was it you talking about this before quarky?

[casebro]

How about the "save water, wash your clothes in re-usable plastic beads" thread?

[BenBurch]

They would self-sort, though, and the smaller beads would wind up on the bottom and the large ones on top.

[richardm]

Originally Posted by BenBurch

They would self-sort, though, and the smaller beads would wind up on the bottom and the large ones on top.

That's okay, they're starting off that way:

Originally Posted by quarky

Make a mix of the glass spheres; some smaller and denser, to form a bed on the bottom; some larger and somewhat denser than water; and a top layer, of larger, lighter balls.

[quarky]

I was definitely thinking of beads larger than the chemistry ones; less static issue.

Cost would be somewhat prohibitive, but if such design made an extra comfy bed, they would last a lifetime; reduce dust; mites; laundry bills.

I haven't looked at the link yet, but will. Much thanks for that.
One of the things I can't quite picture is how much resistance to breathing would be experienced when immersed in the bed of balls.

I've never been in one of those McDonald's playgrounds with the balls. (too tall; they won't let me) How is it breathing down in them?

I have noticed how comfortable it is to lay on sugar sand, even though it is sharp and dense.

[quarky]

I checked out the link; thanks much, Reality Check.

In my idea, there wouldn't be any sheet; the patient would be immersed. This might not be practical for a burn patient, but I wonder if it would make for the comfiest of sleeping possibilities?

[quarky]

Without actually trying out this notion, I'm most curious about what the load would be like on the lung expansion, under the balls. Some displacement would be involved, but not as much as when using a snorkle under water, which only works a foot or so underwater.

[Cuddles]

Just a little nitpick - this would be an artifical fluid, not an artifical liquid. A liquid is a specific state of matter, while a fluid is any substance that deforms continually under an applied shear stress, including liquids, gases, plasmas and fine powders among other things. All liquids are fluid, but not all fluids are liquid.

[quarky]

Quite true.
There are no artificial liquids.
I should have honed my quest in this way:

Is it possible to simulate the experience of floating naked, under warm water, and being able to breathe?

[ben m]

Hi Quarky,

Just a comment. Your statement that glass beads flow "like a liquid" needs to be heavily qualified, and I suspect that the qualifications will kill your idea. Your idea is in the domain of "granular systems", a messy (and fairly new) subfield of soft condensed matter physics. The place where granular systems look most fluid-like is at low density, where the particles can move for a few diameters without crashing into one another. At high density, there's a (poorly understood) "jamming transition" wherein the particles (even if they're frictionless spheres) lock against one another and behave like a solid. Unless your ball bed is being violently shaken, it's going to be more like a solid and less like a liquid.

It's totally possible to lay down on a bed of comfortable-looking balls, but find some of them "jammed" into a semi-rigid pyramid that pokes you in the back. (You can jostle such structures apart, but they don't come apart of their own accord.) There's no general rule, as there is in a liquid, that pressure will be distributed evenly over some surface---it might do so on average, after you've shifted your weight around and wriggled your legs and so on, but any given "jammed" state may well be uncomfortable and pokey. There's no general rule that sorts things by density: there's the competing "Brazil Nut Effect". I suspect your balls-of-varying-density will sort by weight (if they're all the same size), but where will your body sort to? What if your torso "naturally" sinks but your legs naturally float?

Also: one nice thing about being underwater is total freedom of movement. Granular materials restrict movement: if you sank into a ball-bed with your arms outstretched, and you want to get into the fetal position, you'll have to shove and jostle and nudge a near-solid ball matrix out of the way.

So: that's all for solid grains. I wonder if you could do something with very soft, deformable grains. Imagine a bed of slick, squishy, weighted wiffle balls---if compressed, they might be able to deform until there's no pore space *between* them, but they can't drown you because there are always air paths *through* them. With the squishiness/spring constant tuned up right, I can imagine this having something more liquid-like or gel-like than grain-like ...

[quarky]

excellent post, ben m.

As i understand it, spheres of the same radius, when packed as tight as possible, will have aprox. 27% space between them. I can see wherein they might tend to eventually pack tightly, and flow pourly. However, if they were small enough, would they feel pokey?
Would the slightest motion of the person shift them into a less packed, more flowing configuration?
Perhaps such a bed would need to be 'fluffed' a bit before sleep, becoming more packed gradually through the nite, but still providing unusual comfort?

much gratitude for your help.

[Dave Rogers]

I'm not sure whether it's the same concept, but vacuum splints are based on an artificial fluid of this type. The principle is that a sealed bag contains air and a collection of small spheres, which acts as a fluid and deforms around the limb to be immobilised. Evacuating the bag presses the spheres together so that they can no longer flow, and the result is an artificial liquid-to-solid phase transition. At least, that's a customer side view of how they work, based on some speculation and an understanding of physics.

On the question of how difficult it is to breathe in a ball pool, you might note that these are provided for small children to amuse themselves, rather than suffocate themselves, in. In other words, it had better be pretty easy.

Dave

[DavidS]

Originally Posted by ben m

So: that's all for solid grains. I wonder if you could do something with very soft, deformable grains. Imagine a bed of slick, squishy, weighted wiffle balls---if compressed, they might be able to deform until there's no pore space *between* them, but they can't drown you because there are always air paths *through* them. With the squishiness/spring constant tuned up right, I can imagine this having something more liquid-like or gel-like than grain-like ...

I would expect a bed of deformable grains to behave more like a solid than rigid grains, at least up to stresses approaching their yield strength, as deformations facilitate "wedging" behavior at stresses where more rigid grains would simply slide past each other.

Consider moving your hand through beds of marbles or marshmallows; you'd mix one and mash the other.

[CriticalThanking]

Originally Posted by Dave Rogers

On the question of how difficult it is to breathe in a ball pool, you might note that these are provided for small children to amuse themselves, rather than suffocate themselves, in. In other words, it had better be pretty easy.

Maybe Ronald McDonald doesn't really like kids.

CT

[quarky]

Those burger balls are a lot bigger than what i had in mind. There's probably no more overall space than with a container of smaller balls of same diameter, but I'd be concerned that there would be lots more friction to the airflow.

[CaveDave]

How about a "fluidized bed" (not a bed in the same sense as the OP's bed) where a slightly less-dense fluid (gas or liquid) was flowed upward through the media to keep them semi-suspended? Probabably would require a membrane between the media and the occupant, but maybe not.

Just a thought.

Dave