CELLUWIN: 3D printing for cellulose
For a feasibility study on creating 3D structures, using raw cellulose as a starting material, as a proof of principle for the use of cellulose as a modern building material.
Cellulose is the world’s most abundant polymer; it forms the basis for paper, cotton and wood. The vast majority of cellulose is found in the biomass of plants and algae; making cellulose an environmentally friendly, renewable, biopolymer. The mechanical strength of cellulose is due to the self-assembly of individual polymers into tight fibres. Unfortunately bundling of the cellulose polymers renders the cellulose inert and insoluble – making it problematic for use.
Cellulose can be functionalised via dissolution of cellulose fibres into individual polymers via chemical treatment. This allows the cellulose polymers to be manipulated and re-formed into tailor made cellulose composites. This has the additional benefits of decreasing the use of oil derived plastics, but also would allow the use of cellulose from food waste (such as the juicing industry).
Initially this was proposed as a renewable source of material for 3D printing machines, as a replacement / substitute for plastic materials. Preliminary discussion about the use of cellulose in 3D printing quickly revealed an extended audience that would like to further develop the use of cellulose as a modern material.
This project has combined biochemical knowledge about cellulose (the world’s most abundant biopolymer) and advanced 3D printing techniques. The overarching aim is to advance the use of photosynthetically derived polymers in 3D printing as a replacement (where suitable) to widespread use of petroleum derived materials. Cellulose is an inert polymer which during this project has been: activatedinto a usable form, formulated into a working material suitable for storage and, in-activated (cured) into a stable material.
Outcomes, Outputs, Progress
Initial attempts at the activation and formulation of cellulose used citrus (lemons and orange) fruits as a starting material. This was aimed at using a mimic of a current waste product from these fruits, which have been sequentially juiced and extracted for pectins, leaving a cellulose-rich pulp as a waste product. This was a terrible idea as it made the initial activation and formulation a nightmare. As this project aims to facilitate the interface between cellulose and 3D printing, a lack of a working product limited the progression of the entire project. It was decided to use a pure cellulose source as a starting material, and re-visit the idea of waste-cellulose utilization at a later stage.
Using the bacteria Gluconacetobacter xylinus (which naturally forms cellulose biofilms) as a source of pure cellulose, we conducted a range of activation and formulation experiments to develop a protocol for the production of our initial product, affectionately termed “cellu-poop” (it looks fairly disgusting). With prior permission from Prof Jim Haseloff, we have omitted exact details due to the future outlook of the project. However, in brief: cellulose was activated in a range of ionic liquids, mixed in various ratios of activated/raw cellulose, at a range of concentrations, in various buffers.
The most promising outcome from these experiments was the complete solubilisation of cellulose in ionic liquids, which can then be precipitated via contact with water to deposit a cellulose structure. Sadly this approach is vastly un-suited for our laboratory and would require more extensive chemical engineering-style equipment and expertise – but would be ideal to explore in the future.
The current working cellulose 3D material “cellu-poop” is stable at 4oC and can be cured via removal of water to leave a pure-cellulose structure. Thus far we have achieved this via freeze-drying – but with the release of the remainder of the grant we are now working to modify a 3D printer to deposit and cure “cellu-poop” using peristaltic pumps and focused drying techniques (hot air blowers, IR lasers). This marks a large step forward for this project, as now we have the combined might of Marco doing his mechanical magic on the 3D printer and Tom creating cellulose cocktails.
The completed state of the project (due to lack of available time / equipment) is a great start, and has generated preliminary findings to support a larger research grant to continue this project. In short, a systematic approach to formulation, combined with access to a wider range of equipment would be ideal. An exciting side route is the possibility to cure the material via enzymes, allowing for a more biosynthetic approach.
The grant has been spent predominantly on chemicals for the activation and formulation of the cellulose, having tried for 5 months to get a working protocol to create “cellu-poop”. The extra £2k has been spent on 3D-printing equipment and additional chemicals. The grant also covered 6 months membership at MakeSpace, for Marco to build custom components, and light refreshments for networking.