Algal farming has garnered significant interest for both environmental remediation and energy production applications. However, the economic viability of using algae for these applications heavily depends on the efficiency of growing specific algae types. Custom-designed materials and structures allow for controlled microbiological growth processes that result in increased efficiency in water remediation and energy harvesting. Conventionally, two-dimensional synthetic polymer meshes are employed as the scaffolds for algal attachment and growth. These traditional substrata are not biodegradable, and do not provide the optimal shape or surface characteristics for targeted algal growth. This award supports fundamental research on using additive manufacturing to print biodegradable composite scaffolds from cellulose nanocrystals, naturally abundant materials extracted from waste agricultural and forest products. Research results will help advance the development of more economical and biodegradable routes to grow algae for removing contaminants from water and/or producing energy.
The overarching goal of this research is to establish a scientific understanding of combined effects of scaffold composition, shape, and texture on algal growth and scaffold biodegradation in water remediation reactors. The first research objective is to understand the effects of the material composition and processing on the filament properties. To achieve this objective, cellulose nanocrystal/polylactic acid composite filaments will be produced using extrusion after three initial mixing methods: 1) dry mixing, 2) spray drying, and 3) polyethylene oxide/cellulose nanocrystal masterbatch incorporation. Measurement of rheological, thermal, morphological, and contact angle properties will be performed using standard methods. The second objective is to understand the effects of rheological properties (particularly the ratio of the elastic to viscous modulus) of the filaments on the quality (including surface defects) of the scaffolds printed by additive manufacturing (fused deposition modeling). Several types of composite filament will be printed into algae growth scaffolds containing a range of surface structures. The characteristics of the deposited layers (e.g. layer thickness, road width, and fill voids) will be measured using optical microscopy and chromatic confocal profilometry and correlated to surface defects. The third objective is to understand how scaffold shape and chemistry affect algal growth and scaffold degradation. The scaffolds will be put into a laboratory-scale flow reactor containing algae growth media. At one week increments, the scaffold will be removed and examined by optical microscopy. The algae will then be removed and the mass harvested from different regions recorded. Changes to the scaffold will also be assessed using microscopy and mass measurement.
