Tiny rubber spheres used to make a programmable fluid | Hacker News Reader

Tiny rubber spheres used to make a programmable fluid

arstechnica.com

76 pointsnobody999917 comments

From TFA:

"“I did my PhD in France on making a spherical shell swim. To make it swim, we were making it collapse. It moved like a [inverted] jellyfish,” says Adel Djellouli, a researcher at Bertoldi Group, Harvard University, and the lead author of the study. “I told my boss, 'hey, what if I put this sphere in a syringe and increase the pressure?' He said it was not an interesting idea and that this wouldn’t do anything,” Djellouli claims. But a few years and a couple of rejections later, Djellouli met Benjamin Gorissen, a professor of mechanical engineering at the University of Leuven, Belgium, who shared his interests. “I could do the experiments, he could do the simulations, so we thought we could propose something together,” Djellouli says. Thus, Djellouli’s rubber sphere finally got into the syringe. And results were quite unexpected."

The paper discussed in the Ars piece can be found here[0].

[0] https://www.nature.com/articles/s41586-024-07163-z.epdf?shar...

“I told my boss, 'hey, what if I put this sphere in a syringe and increase the pressure?' He said it was not an interesting idea and that this wouldn’t do anything,” Djellouli claims."

If someone tells you that your line of research is uninteresting, just do the research anyway.

Seconded. More than once I've been talked out of pursuing a line of research only to see someone else publish decent results on the same thing a couple of years later.

If someone tells you that your line of research is uninteresting, that means results would be surprising – i.e., that's a sign that it is interesting. (Unless they've tried it and empirically found that it's "uninteresting" – which is somewhat interesting in itself, even if it's not sexy enough for today's academia.)

> If someone tells you that your line of research is uninteresting, just do the research anyway.

My graduate advisor said that to me and put me on some other stuff he wanted to work on. It really took the wind out of my sails, and I never really had the passion for the new work that I did for my original idea.

My final year he got a new PhD student and let her work on the idea. She was quite successful in that area. He never said anything to me about it.

TLDR if you have an idea you're passionate about it, ignore the haters and just do it. Even if it doesn't succeed, you'll have the satisfaction of knowing you pursued something YOU found interesting.

If someone experienced in a field of research tells you something is possible, they're very probably right.

If they tell you it's not possible, it's 50/50.

Adapted from:

Clarke's first law: When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.

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I don't think you need to be elderly - just set in your ways.

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A valuable conversation would be why they think it wouldn't work. That will give you a lot of surface area to mine for clues to make it work.

The paper and videos are here:

https://bertoldi.seas.harvard.edu/publications/shell-bucklin...

Note that this is not "gripper" like "five-fingered robot hand". A better description might be "vise" (like the kind in a woodworking shop). The egg gets pressed between two linear actuators each with one degree of freedom.

From the title it sounded like the fluid could be given procedural instructions and then carry them out, but after watching the videos, it seems that what is happening is that the pressure/volume curve can be modified in hydraulic systems by adding these spheres to the hydraulic fluid, which collapse at a certain pressure threshold thereby reducing the output pressure of the system around a specific range, to avoid crushing the target object. The spheres can't be given different code. But the pressure/volume curve of the hydraulic fluid can be modified by using spheres with different properties.

so "programmable" in the sense that a VCR is "programmable". Configurable

Outside of the title, they use the word "tunable" which is more accurate.

> “You can tune pressure at which the spheres activate by changing their radius and thickness of their walls.

I immediately thought this.

The whole thing seems like such an intuitive idea. I really like the idea of mixing sizes to induce multiple pressure “plateaus”.

Also the drama of its inception is delectable.

The paper linked in another comment has some excellent visual aides. Wish we had a video.

The paper’s graphs show a hysteresis that looks a lot like many semiconductor curves. What a neat technology, this might make for some interesting hydraulic control solutions.

Videos: https://bertoldi.seas.harvard.edu/publications/shell-bucklin...

Sometimes I wish I had gone into materials science like one of my HS teachers suggested. This is pretty dang cool

Pretty neat. Could you do this outside of a pressure vessel by filling the balls with water and hitting it with microwaves? Then we can get crawling terminator fluid.

So this other guy: he's a Terminator like you, right?

Not like me. A T-1000, advanced prototype.

You mean more advanced than you are?

Yes. A mimetic polyalloy.

What the hell does that mean?

Tiny rubber spheres.

More like a mimetic composite polysludge.

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