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Comment by the__alchemist | Hacker News Reader

Nearly all passive water-from-air devices described in articles are based on false claims. Peltier-based, desiccant/absorption/adsorption based, etc. All end up not working, or not existing. This has been common for ~10 years.

Which category does this fall into?:

  - Fraud
  - Incompetence / misunderstanding that wasn't cleared up prior to publishing an article
  - Neither; this works as expected

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The claim on this one is that the textile is supposed to be substantially better than extant desiccants:

> Compared with conventional water-harvesting materials, the textile showed a three- to 10-fold improvement at scale.

Technology Connections has a video on this general technique with a demo from a typical commercially available unit [0]

The "in a jacket" angle is novel... there's no blower. Even though this desiccant may be "3 to 10" times more effective, the passive nature is going to presumably make the rate of extraction quite poor compared to units with a blower to keep moist air moving over the substance.

Based on the wording, this improvement is due to some kind of gradient where moisture is collected on the surface of the jacket/textile, then channeled towards some internal chamber where the desiccant is constantly being heated to extract moisture - without the need to heat the exposed textile to extract water from that portion.

Of course increasing the rate of collection doesn't matter much on its own! You can't drink a damp textile. What takes energy is the removal of the moisture from the desiccant - and how much energy that requires is a detail suspiciously absent from the article (presumably because the efficiency isn't improved versus other desiccants).

So personally, I have trouble imagining this is as efficient as the blower-based commercial units, which are... far less efficient than "normal" compression cycle dehumidifiers (in the above video, real world testing shows the "normal" dehumidifier is 5 times more efficient than the desiccant one).

[0] https://www.youtube.com/watch?v=JzClLWL-Eys

Damn... I was hoping we'd finally get Stillsuits.

https://dune.fandom.com/wiki/Stillsuit

Yea, usually the next step is starting a Kickstarter campaign and then rug-pulling.

https://www.youtube.com/watch?v=LVsqIjAeeXw

The design seems reasonable. It seems like a scaled down version of this MIT one that uses similar principles:

https://news.mit.edu/2025/window-sized-device-taps-air-safe-...

So my vote is for working as expected.

Many thanks for your link to the article, it was a very interesting read; fascinating to learn how glycerol interacts with lithium salts...

The team’s new design significantly limits salt leakage. Within the hydrogel itself, they included an extra ingredient: glycerol, a liquid compound that naturally stabilizes salt, keeping it within the gel rather than letting it crystallize and leak out with the water. The hydrogel itself has a microstructure that lacks nanoscale pores, which further prevents salt from escaping the material. The salt levels in the water they collected were below the standard threshold for safe drinking water, and significantly below the levels produced by many other hydrogel-based designs.

So uh, how do they get the salt out of the nanostructure? This design seems amazing but it seems like many of these designs have issues with salts accumulating and clogging up parts thereby requiring some manual maintenance or replacement parts

The salt is there to be hygroscopic, they don't want the salt out. The structure is there to keep the salt in.

> Over this period, the device worked across a range of humidities, from 21 to 88 percent, and produced between 57 and 161.5 milliliters of drinking water per day. Even in the driest conditions, the device harvested more water than other passive and some actively powered designs.

so its making a shot of water ever couple days, provided its not too dry?

you need to scale way way up, not down

A shot is ~ 35 ml to 50 ml, so one to three shots a day. :p

1.5oz in the US, which is about 44mL

That's about the average of 35mL and 50mL. ;)

If a human needs about 1L per day on a minimal survival scenario, we're talking 20+ jackets right?

Just get your friends to wear them too.

who gets to drink today?

It's the new drinking game, obvs.

Both devices handwave on how the cooling required to condense the water occurs.

I believe this uses absorption; not cooling [condensation].

Abortion release the same amount of heat than condensation. So you can cool the material before and get condensation or absorb the water and cool the material later.

Sweating keeps you cool, absorbing the sweat will cancel the cooling effect and you will overheat and may die.

It is a dessicant dehumidifier, useless for the same reason as this MIT/Berkley thing from 9 years ago.

https://www.youtube.com/watch?v=EGTRX6pZSns

I'm glad someone else pointed it out, I would be skeptical of these claims. It will always be constrained by thermodynamics and local humidity. And it seems to only absorb the vapor at night and then release water in sunlight. Even if it produces what they claim, it's still barely enough to supplant the daily needs, and the jacket is probably not worth saving half liter of water.

Here's one that uses exotic materials that the developer got the 2025 Nobel chemistry prize for:

https://www.nature.com/articles/d41586-023-03875-w

It isn't passive. The paper states it needs to be heated to 60C and then you extract the water. They use a "DC power source" so you're still putting a battery into the jacket.

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