3D printing with cellulose | Hacker News Reader

3D printing with cellulose

news.mit.edu

127 pointsudfalkso39 comments

This claim is pretty incredible:

“After we 3-D print, we restore the hydrogen bonding network through a sodium hydroxide treatment,” Pattinson says. “We find that the strength and toughness of the parts we get … are greater than many commonly used materials” for 3-D printing, including acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA).

Maybe a bit too incredible.

How do thick-walled materials have their hydrogen bonds restored? This process seems rather more involved than regular 3D printing.

The thing in that photo is quite porous. Also paper is very penetrable by water, so it wouldn't be too surprising.

But, well, if it's that simple, just soaking cellulose acetate in NaOH should have a huge number of applications. Maybe even more interesting than this 3D printer.

(Gotta try this at home later...)

Maybe it doesn't penetrate through the walls entirely - perhaps just the outsides? Sort of analogous to constructing a wide brick wall with the interior filled with rubble?

Sounds like they soak the print in a NaOH solution. I imagine if the material is porous enough to evaporate acetone, it's also porous enough to absorb a NaOH solution.

Just in case someone else gets bogged down in chemistry, NaOH is better known as lye or caustic soda.

They called it Sodium Hydroxide in the article as well. :)

If you scale it up you could 3d print houses from Cellulose. Since 3d printing is inexpensive and the material abundant you can 3d print an outer isolation layer of a honey comb structure, bio inspired from bees. If the outer isolation layer becomes degraded from years of contact with wind and rain you can simply print a new one.

Is 3d printing really the most efficient way to make such a structure? Could you not pack straws together and then squish them? Could you not make a corrugated sheets like cardboard?

Mass 3D printing an item that can already be manufactured through e.g. injection moulding or assembling standardised parts is never going to be efficient at scale. That's not what it's for. Where 3D printing excels is at producing one-offs or short runs, immediate production (no time consuming buildout phase manufacturing moulds and setting up production lines), on-site or mobile manufacturing, or making designs that are not amenable to traditional manufacturing processes such as objects with complex geometries or internal voids.

Honestly, cellulose is one of the least desired materials I'd want my house made of. After all the additives needed for making it good enough, it will be some kind of ceramic already, so why not start there?

We can already 3D print concrete. Centralized manufacturing still beats that all hands off... And people still insist on manually assembling bricks for a lot of reasons.

Could we build spaceships with that ?

The main factor when designing a spaceship is mass; getting mass into orbit is currently very expensive. You want to use materials which have very high strength to weight ratio, such as aluminium, and carbon fibre.

Can we build a space elevator with this?

Not with cellulose, and likely not from the ground up. Space elevators are typically imagined as being bootstrapped from a starter cable lowered from orbit. And the tensile strength for a safe one is an order of magnitude or two higher than good steel, to say nothing of plant fibers.

Could we build a space elevator with artificial silk?

https://www.slu.se/en/ew-news/2017/1/spinning-spider-silk-is...

This is fantastic. If the properties and aesthetics are good, I can see a lot of demand driving the filament manufacturers to adopt this material. Paste-like extruders for open-source machines exist on the market today for chocolate and clay.

Only concern for me is it sounds like post-processing is required.

From the article:

> As the acetone quickly evaporates, the cellulose acetate solidifies in place. A subsequent optional treatment replaces the acetate groups and increases the strength of the printed parts.

Effectively, dipping the thing in lye.

I've been researching thermoforming polymer materials for the last few weeks, and there is a well established category of materials known as PLA.

Polylactides (PLA) or polylactic acids represent a relatively new group of thermoplastics for packaging applications obtained from renewable resources. In extensive tests the functional and thermoforming properties of PLA are compared with those of other polymers. They are a biodegradable/compostable polyester manufactured from plant based resources. At 60°C and relative air humidity of 80% PLA will degrade completely after 60 days.

PLA's properties make it suitable for various thermoforming applications, particularly cups for cold bevarages and trays for fruit and vegetables. To produce high-molecular PLA, a process is used that is sustainable, solvent-free, and environmentally friendly.

PLA can be obtained from cassava, corn, maize, sugar beet, sugar cane, wheat, or agricultural byproducts containing natural plant sugars.

Although PLA has been known for more than a century, it has only been of commercial interest in recent years, in light of its biodegradability.

While PLA is one of the most promising bio-basedplastics, its main disadvantages are high price and unsatisfactory mechanical properties.

My understanding is that thermoforming is however only really utilized for sheet-based PLA material with essentially non-convex configurations. Also, it tends to degrade over 60 degrees celsius.

I wonder how this process and its output differs step-wise, limitation wise, and in terms of resulting material's mechanical properties. From the sounds of it, it's essentially a layering process and too early to judge limitations, though a small temperature range could perhaps be expected.

maybe I'm missing something, but PLA is just 3d printer filament. There's only two plastics commonly used for extruder-style 3d printers, and they're ABS and PLA.

This is a bit out of date. Nylon, PETG, TPE/TPU and polycarbonate are quite common for home 3D printing now as well as a number of hybrid materials.

Polypropylene is coming in too. PVA for water-soluble (mostly as support material).

Looks like the website is under heavy load.

Here's a mirror: https://archive.fo/eoohY

Sounds promising for both 3D printing applications and the need for non-petroleum based plastic-like materials.

Just a funny coincidence but, did you see "TreeMaker" origami software just below this thread? :-)

For the last few months I was wondering if there were a way to implement logic in cellulose ..

What application do you have in mind?

Cellulose absent water is extremely inert, so inert that we use it as long term information storage, it is also an extremely good insulator.

You'd be more likely looking at using the cellulose as a non-conducting carrier than as part of the logic itself.

Are there an any advantages to using hydrodynamic vs. electrodynamic forces for carrying signals? Hollow cellulose nanotube structures could be printed to carry fluid to different areas of a three dimensional circuit.

Would you be able to sacrifice some of the raw "speed" you gain from using electrical current to carry the signals in a traditional PCB if it meant you could work with significantly reduced heat? Or is my rudimentary understanding of the physics here betraying me? Friction is going to exist, so it's quite possible that these types of organic fluid logic gates would be useful for other reasons, but not in the ways I've imagined.

Without some(all?) of the electromagnetic changes associated with the continued reduction of die size for traditional electrical circuits, can you build significantly denser (and eventually more powerful) mechanical circuits with fluid-filled cellulose nanotubes?

It's prone to rotting in the presence of fluid, if you make it wet I think that would be a quick and messy ending.

Good point. Would an oil-based transport fluid mitigate that to some degree, or is the organic nature of cellulose going to be a liability to hurdle to making a durable component regardless of the fluid used?

The problems are size and shape change as it saturates and losing structural integrity (soggy...). Capacitors are a nice example, they're always wrapped in something else both to contain the fluid and to keep things in one place.

Any kind of acidity would also be taboo. It would be very hard I think to make something like this but I'm more than willing to admit that none of these are 'dealbreakers'. That's why I asked about the application, after all, if that's the only way to do it and the application is valuable enough then maybe there is a reason to invest a large amount of $ for R&D.

so it's practically paper?

Most similar to cellophane or celluloid foil used for making film substrate. Except thick. Try gluing many layers of film together, see how resilient it is.

No, it's similar to hard plastic.

I thought it was plant based

Cellulose acetate was one of the first materials used for many of the things we use petroleum based plastics for now. Early Lego were cellulose acetate.

It's still used for lots of things.

Cellulose is a very useful chemical. It was generally replaced by petrochemical synthetic polymers for many of its original applications because the latter may be more stable at higher temperatures, under UV light, in contact with certain common chemicals (like water), etc. And most of the petro-plastics are cheaper to manufacture.

Cellulosic thermoplastics often appear in products where you don't want the plastic component to last forever, particularly textile fibers.

https://en.wikipedia.org/wiki/Cellulose_acetate

https://en.wikipedia.org/wiki/Cellulose_triacetate

https://en.wikipedia.org/wiki/Rayon

https://en.wikipedia.org/wiki/Cellophane

https://en.wikipedia.org/wiki/Lyocell

This 3D printing application seems similar to processes used to produce rayon and cellophane, but instead of producing the more universally useful fiber and sheet forms as a commodity, it forms an end-product directly and then stabilizes it chemically.

Both plastic and petroleum jelly are petroleum-based, but have drastically different properties.

The cellulose polymer acts as hard plastic.

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