<p>It is difficult enough to make 3D-printed objects water-tight (unless you paint them). Making them permeable to air but not water vapour is too big an ask, I think.</p>

CC BY-SA 4.0
2019-08-07T13:38:55.463Z
Thanks. I also posed a more generalized question in the engineering stackexchange: https://engineering.stackexchange.com/questions/29523/what-is-a-material-that-allows-air-to-pass-but-not-water-vapor/29537#29537. So, I think a silicone syringe is the best option to try
K Mmmm
CC BY-SA 4.0
2019-08-06T15:43:29.820Z
2019-08-06T15:43:29.820Z
Mick
<p>In some situations it useful to have a material in which air passes but water, and water vapor, does not. Printing cell membranes or cases for something that must be immune to humidity changes (like something that holds a highly oxidative metal) are two examples. </p>

<p><strong>Teflon</strong> (PTFE) is a material that has this property. But PTFE is horrendous to 3D print.</p>

<p><strong>Silicone</strong> is another material that has this property. 3D printing silicone can be done with a syringe mechanism. But there are also thermoplastic rubbers (e.g. TPU, TPE) that are designed to mimic Silicone.</p>

<p>Are there any filaments on the market which naturally form holes with the porous diameter for this feature? Is there any way to manipulate the diameter of this hole, even starting from pellets? Are some filaments more likely than others to have this feature?</p>

CC BY-SA 4.0
2019-08-06T17:14:46.923Z
I doubt you'll find many materials - aside from 3d filaments - which can separate gaseous H20 from the other molecular gases present in our atmosphere.
Carl Witthoft
CC BY-SA 4.0
2019-08-06T18:03:59.823Z
The water vapor molecule is smaller than an Oxygen or Nitrogen molecule. There is no such material in this world. Can you cite a source of that property of PTFE?
user77232
CC BY-SA 4.0
2019-08-07T13:40:23.863Z
Good point about the size of water, but one thing water is, is polar. So its polarity can be used to filter it out more easily despite its size (like in a cell's phospholipid membrane).
K Mmmm
CC BY-SA 4.0
2019-08-07T13:56:26.170Z
Well, there you go, then-- just use phospholipid-based filament.  (Yes this is a stupid joke)
Carl Witthoft
<filament><print-material><material><filament-choice>
What filaments allow air to pass but not water vapor?
K Mmmm
# What filaments allow air to pass but not water vapor?

(Asked by: username_0 on 2019-08-06)

In some situations it useful to have a material in which air passes but water, and water vapor, does not. Printing cell membranes or cases for something that must be immune to humidity changes (like something that holds a highly oxidative metal) are two examples.

**Teflon** (PTFE) is a material that has this property. But PTFE is horrendous to 3D print.

**Silicone** is another material that has this property. 3D printing silicone can be done with a syringe mechanism. But there are also thermoplastic rubbers (e.g. TPU, TPE) that are designed to mimic Silicone.

Are there any filaments on the market which naturally form holes with the porous diameter for this feature? Is there any way to manipulate the diameter of this hole, even starting from pellets? Are some filaments more likely than others to have this feature?

**Tags:** filament, print-material, material, filament-choice
> **Comments:**
> **username_1**: I doubt you'll find many materials - aside from 3d filaments - which can separate gaseous H20 from the other molecular gases present in our atmosphere.  
> **username_2**: The water vapor molecule is smaller than an Oxygen or Nitrogen molecule. There is no such material in this world. Can you cite a source of that property of PTFE?  
> **username_0**: Good point about the size of water, but one thing water is, is polar. So its polarity can be used to filter it out more easily despite its size (like in a cell's phospholipid membrane).  
> **username_1**: Well, there you go, then-- just use phospholipid-based filament.  (Yes this is a stupid joke)  

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## 1 answers

### Answer by username_3 on 2019-08-06. Score: 5 | Accepted answer

It is difficult enough to make 3D-printed objects water-tight (unless you paint them). Making them permeable to air but not water vapour is too big an ask, I think.

> **Comments:**
> **username_0**: Thanks. I also posed a more generalized question in the engineering stackexchange: https://engineering.stackexchange.com/questions/29523/what-is-a-material-that-allows-air-to-pass-but-not-water-vapor/29537#29537. So, I think a silicone syringe is the best option to try  

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