3M Microbial Material Matter: Evaluating Growth, Colouration, and Coating Methods for Bacterial Cellulose

This study explores bacterial cellulose (BC) as a biomaterial for design applications, assessing how natural colouration and coatings influence its aesthetic properties, durability, and long-term performance. BC was modified with organic additives during growth (in-situ) and treated with various coatings post-drying (ex-situ). Unlike typical studies that assess biomaterials at a presumed point of readiness, this one-year evaluation revealed time-dependent material changes that were initially unnoticeable, emphasizing the need for long-term observation. Various natural pigments were incorporated in-situ, including beetroot, hibiscus, saffron, red cabbage, curry, coffee, henna, matcha, curcuma, and food dyes. Fermentation occurred at 21–26°C, pH 3.8–4.6, over 18–25 days. Beetroot-infused fermentation (330mL/L water) produced the most efficient BC growth, yielding ~8mm thick sheets in 25 days, surpassing ~5mm from black tea-based fermentation. Hibiscus extract (20g/L) provided a stable red hue, while other pigments varied in fade resistance and material strength. Ex-situ coatings, including wax, beeswax, and coconut oil, were applied post-drying. While coconut oil initially preserved flexibility better than wax, both coatings resulted in brittleness over time, highlighting the need for improved protective treatments. Post-growth dyeing with hibiscus and beetroot, enhanced coloration but increased fragility. BC sheets were integrated into wearables, lighting, and wall panels to evaluate performance, and monitored over one year for colour stability and environmental resistance. This study highlights the potential of natural pigmentation for BC, with beetroot and hibiscus proving the most effective in-situ pigments. However, coating limitations emphasize the need for further research to improve long-term flexibility and material integrity for sustainable design applications.