Temperature-Controlled Microalgae Biofilm Adsorption/Desorption in a Thermo-Responsive Light-Guided 3d Porous Photo-Bioreactor for Co2 Fixation

Microalgae biofilm-based culture provides efficient CO 2 reduction and wastewater treatment for its high photosynthetic efficiency and density. As supporting substrate for microalgae biofilm, porous materials have big available adsorption area, but mutual shading make it difficult to transmit external light to the internal surface for microalgae photosynthesis. Thus, a light-guided particles (SiO 2 ) were introduced into photosensitive resin to fabricate light-guided ordered porous photobioreactor (PBR) by 3D printing technology in this study. The space utilization of the PBR significantly enhanced and the effective microalgae adsorption area was increased by 13.6 times. Further, a thermo-responsive hydrogel was grafted onto the surface of the substrate to form a smart temperature-controllable interface that could enhance microalgae adsorption and desorption in both directions. When the thermo-responsive layer received light, it would generate heat due to the hydrogel’s photo-thermal effect. And the surface temperature would then raise to 33°C, higher than hydrogel phase transition point of 32°C, making the surface shrinking and more hydrophobicity for microalgae cells attachment. The microalgae cells adsorption capacity increased by 103%, resulting in a high microalgae growth rate of 3.572 g m -2 d -1 . When turn off the light, the surface temperature would cool down to below 20 °C, the surface would shrink. And the biofilm shows a 564.7% increase in desorption ability, realizing temperature-controlled microalgae harvesting.