An analytical and experimental study on 3D-printed custom surfaces for benthic algal biofilms
Type of DegreeDissertation
Industrial and Systems Engineering
MetadataShow full item record
Due to their fast growing rates and regeneration, algae are a promising avenue for biofuels, aquatic pollution recovery, and a source of protein nutrients, among others. Cultivation of benthic algal communities, in particular, show promise for these functions, yet control quality and yield is strongly dependent on substrata characteristics that affect algal attachment and growth. No previous research efforts seem to have taken advantage of the recent developments in additive technology to support algal attachment and colonization. Additive manufacturing can allow for the design and control of surface features and provide a platform for developing substrata with customized surface topographies for algal colonization. This study seeks to, first, establish the feasibility of colonizing 3D-printed custom substrata with algal biomass. Then, using 3D printing, potential approaches of controlling species composition in cultivation systems through design of substratum characteristics to select for species in colonization were investigated. It was done by designing and 3D printing substratum topographic sections to test for selectivity of colonization of periphyton algae in natural streams. In another effort, relationship between surface topographic features with attachment and colonization of benthic algal species were studied. 3D-printed patterns were used as molds for making growth plates with clay. The clay-made plates were then placed in a laboratory-based bench scale bio-cultivator exposed to a culture of benthic algae for three weeks for each replicate for a total three replicates. After collection, the biomass was carefully harvested in each section and oven dried and then weighed to find the exact amount of algae biomass per each section. Finally, the performance of 3D-printed materials (polymers) in such custom surfaces under collisions was characterized to better design for different applications. Based on the results, the preliminary work seems to indicate that: (i) 3D printed substrata can be successfully colonized by algal communities; (ii) there is a roughness effect on the colonization rate of benthic algae; (iii) substratum roughness can be designed for optimal interstitial spacing between surface asperities, and (iv) increased efficiencies in the packing of biomass can be achieved by complex 3D-printed geometries that provide very high surface area in compact volumes. Also, in research on preferences of algal species from natural streams, twelve species of periphyton algae in four divisions were identified across all topographic sections, and the distribution of these twelve species and relative abundance varied as a function of topographic feature size, with the greatest diversity observed on the surfaces with topographic feature sizes of 500 μm. Of the twelve identified species, two showed abundance patterns as a function of topographic feature size that were significant. Microspora wileana displayed a preference for surfaces with topographic feature sizes less than 500 μm, and Stigeoclonium tenue displayed a preference for surfaces with topographic feature sizes less than or equal to 100 μm and greater than or equal to 1500 μm. These results suggest that substratum design using 3D printing or other technologies may be useful to influence species composition and dominance relationships in mixed communities in engineered periphyton cultivation systems. The behavior of five different 3D-printed polymers have been analyzed theoretically and experimentally under low speed collision. Impact of a rigid rod on a flat made of 3D-printed materials has been analyzed. An experimental setup has been designed in order to capture the motion of the rod during the impact using a high speed camera. Image processing is developed to estimate the velocity before and after the impact as well as coefficient of restitution. Permanent deformations after the impact have been scanned with an optical profilometer. A theoretical formulation for the contact force during the impact has been proposed. The impact has been divided into two phases: compression and restitution. For the compression phase the materials considered elasticplastic and the restitution phase has been considered to be fully elastic. The experimental results have been used to measure the damping coefficient. Results indicate that the proposed formulation for the contact force matches the materials behavior.