Spirulina‐based composites for 3D‐printing

Abstract

With material consumption increasing, the need for biodegradable materials derived from renewable resources becomes urgent, particularly in the popular field of 3D-printing. Processed natural fibers have been used as fillers for 3D-printing filaments and slurries, yet reports of utilizing pure biomass to 3D-print structures that reach mechanical properties comparable to synthetic plastics are scarce. Here, we develop and characterize slurries for extrusion-based 3D-printing comprised of unprocessed spirulina and varying amounts of cellulose fibers (CFs). Tuning the micro-morphology, density, and mechanical properties of multilayered structures is achieved by modulating the CF amount or drying method. Densified morphologies are obtained upon desiccator-drying, while oven incubation plasticizes the matrix and leads to intermediate densities. Freeze-drying creates low-density foam microstructures. The compressive strengths of the structures follow the same trend as their density. CFs are critical in the denser structures, as without the fibers, the samples do not retain their shape while drying. The compressive strength and strain to failure of the composites progressively increase with increasing filler content, ranging between 0.8 and 16 MPa and 12%-47%, respectively, at densities of 0.51-1.00 g/cm 3 . The measured properties are comparable to other biobased composites and commercial plastic filaments for 3D-printing.

Long-Term Hindrance Effects of Algal Biomatter on the Hydration Reactions of Ordinary Portland Cement

“…The weakening mechanical performance of the biocomposites is the result of distinct hydration products instead of the structural defects alone. Chlorella and spirulina both have a high concentration of carbohydrates ranging from 13.6 to 54.4 wt % depending on strains and growth conditions, and for both, more than 50% of the carbohydrates have glucose monomers. ,− In alkaline conditions in cement pastes, glucose degrades into acidic forms such as parasaccharinic acid or glycolic acid, as demonstrated by Yang and Montgomery . Therefore, we reasonably anticipate the acidification of glucose-based carbohydrates in both cases of chlorella and spirulina when mixed with the cement paste.…”

“…Finally, to explain the different aging behavior between chlorella and spirulina and the higher strength evolution in spirulina composites, we note the different carbohydrate content in the two types of biomatter. We analyzed the carbohydrate content of our biomatters via high performance liquid chromatography (HPLC) (results shown in Figure S5 for chlorella and prior work from Fredricks et al 40 for spirulina) and found that chlorella contains 21.7 wt % carbohydrates, 10.8 wt % of which are glucose-based, while spirulina has 14 wt % carbohydrates, 6.1 wt % of which are glucose-based. This result supports the more significant suppressing effect when chlorella is introduced in cement as compared to spirulina.…”

“…These processing routes are typically low yield, as only a small fraction of the dry mass is extracted as a product, while the remaining parts of the biomass are manufacturing waste. A recently emerging and more sustainable alternative − suggests using fast-growing, untreated plant, algal, or microbial biomatter, in the form of intact cells or tissues, as a polymeric matrix or filler material, aiming to capitalize on raw biomatter to function as a renewable material platform that potentially can lead to wasteless processes. Photosynthetic biomatter in particular, such as plant or algal cells, can effectively serve as carbon-negative matrix materials or additives.…”

Fabricating Strong and Stiff Bioplastics from Whole Spirulina Cells

“…[ 23,56 ] Specifically, the layered conformation and terminal oxygen planes in the tetrahedral structure of montmorillonite (MMT), our nanoclay of choice, would allow enhanced surface interactions and hydrogen bonding with the protein‐ and carbohydrate‐based spirulina matrix. [ 30 ] We note that sonication of the nanoclay and spirulina in water are necessary to promote filler dispersion and enhance interactions by dissociating the cells. Indeed, upon freeze‐drying and hot pressing the nanocomposite bioplastics, we observe that a 5 wt.% nanoclay concentration leads to an improvement of the average flexural strength from 35.1 ± 4.5 to 57.2 ± 7.4 MPa (63% increase), a increase in work to fracture from 0.15 ± 0.03 to 0.29 ± 0.06 MJ m −3 (93% increase), and an increase in stiffness from 3.9 ± 0.7 to 5.3 ± 0.3 GPa (36% increase) over sonicated and freeze‐dried spirulina without the nanoclay (Figure 4f, solid blue line).…”

“…Fredricks et al. [ 30 ] demonstrated that unmodified spirulina cells can also be used in additive manufacturing to create inks for direct ink writing. The printed structures had mechanical properties and micromorphologies dependent on the drying method.…”