ePTFE (like the other two, but not exactly)

While PTFE and ETFE have made significant contributions to architecture, the range of architectural types they have affected is rather limited. They have been applied exclusively to tensile and pneumatic structures, and exclusively as impermeable membranes. While this setup has proven effective, advances in the use of PTFE in other fields has demonstrated potential applications architecturally.

The most significant development prompting this suggestion, is the arrival of Gore-Tex in the wearables scene. Gore-Tex is actually a proprietary name for ePTFE, which just stands for “expanded PTFE”, i.e. expanded Teflon.

That should clear everything up.

That should clear everything up.

Basically, some bright fellows invented a method of precisely pulling Teflon through a set of rollers in a way that begins to pull the membrane apart, but results in a strong web of material that now has a microporous structure.

Nothing funny left to say. This is beautiful.

Nothing funny left to say. This is beautiful.

This microporous structure turns out to have properties that seem almost magical for heavy-duty winter clothing. The pores in the ePTFE are small enough that it strongly-resists liquid water from penetrating (because of surface tension). Not only that, but because water droplets are in contact with more air (the micro-pores) than actual surface, the material actually has hydrophobic qualities, and sheds water quickly and readily. What makes this truly impressive, is that the pores still allow water vapor to float easily through. This means that jackets made with this material will roll rain right off, but will let the users sweat evaporate directly through, rather than trap the moisture uncomfortably (and in some cases dangerously) inside.

This nut-job is probably wearing Gore-Tex

This nut-job is probably wearing Gore-Tex

Gore-Tex has quickly become the standard of quality outerwear, because of its performance and durability. This begs the question, why couldn’t we begin to take advantage of these qualities architecturally?

One team of graduate students is proposing an architectural application that takes advantage of some of the beneficial qualities of ePTFE (hydrophobicity and durability) and combines it with the water repellent structure of a bird feather, to create a surface that can repel water, but still allows for the passage of fresh air and light.

Bird feathers display an interesting example of hydrophobicity, in that they shed water because of their physical structure and dimensionality, not because the feather lacks holes.

feather2

In the above image you can see how water droplets neatly bead up on a feather. This is because the barbs (the fine strands that make up the feather) are aligned neatly next to each other with a small, consistently spaced gap between them. That gap is small enough to resist water penetration, and the increased air-contact at the water/feather barrier increases the hydrophobicity, causing the water to bead up and roll off.

The team decided to apply this logic at an architectural scale, by developing a fabric made from strands of ePTFE (already displaying hydrophobic qualities) with finely controlled spacing that would resist the penetration of liquid water, but allow for fresh air to readily circulate, and maintain visual connection with the sky above

Photo Dec 11, 5 21 01 PM

Prototype of the water repellent surface.

Photo Oct 22, 1 48 43 PM

droplets on the prototype

This material, which would require significant development to become feasible, still succeeds in blurring the existing boundaries of architecture. The difference between interior spaces becomes less clear as the sky above is visible, and the breeze blows freely through, while rain is shed discreetly out of the way. This type of disruption may not lead to revolutions, but has the potential to significantly alter the way people experience their environment. At the very least, it shows us that Teflon has not revealed to us yet all it has to share, and will hopefully bring many exciting architectural advances in years to come.

 

 

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