Using oscillatory flow and non-Newtonian media to enhance industrial processing of microalgae and other microswimmers

微生物在生物生态系统和工程应用中的重要性已得到充分证明。微藻是一种特殊类型的微生物，目前在光生物反应器中以工业规模生长，用于生产化学品、污水处理、碳捕获和生物燃料生产。特别是微藻生物燃料生产相对于更传统的原料（如甘蔗）而言，由于在可持续性方面的潜在优势，其势头正在增强。然而，改变游戏规则的藻类燃料技术工程，例如在设计与现有燃料真正竞争的优化培养生物反应器时，需要更好地理解和表征藻类悬浮液的流变学。因为在所谓的“主动”悬浮液中，游泳的微藻能够使用鞭毛自我推进，它们与流场的相互作用比非运动颗粒的相互作用复杂得多，这既是一个机会，也是一个挑战。例如，利用游泳活动可能会导致新的分离和“转向”方法。然而，尽管公认的潜在的新的个人和集体行为的游泳过程工程，藻类悬浮液流变学的实验研究仍然有限，仍然存在基本的难题。该项目的目的是显着提高我们的知识和理解的复杂流动条件下，特别是在振荡流，混合剪切延伸流和流动的非牛顿介质，如粘弹性悬浮液的游泳藻类的流动行为。为此，一种单细胞藻类，盐藻，将被检查，以确定其游泳能力在不同的刺激下。这项工作将主要以实验为基础，以流变学、显微镜和测速方法为平台，绘制出藻类的反应。我们将使用实验数据中的关键参数，通过与建模和理论专家的合作，为复杂介质中的“微型游泳者”运输和扩散的新模型提供信息。

The importance of microorganisms is well-documented, both in biological ecosystems and in engineering applications. Microalgae are a particular type of microorganism currently grown on an industrial scale in photo-bioreactors for the production of chemicals, effluent treatment, carbon capture and biofuel production. Microalgae biofuel production in particular has been gaining momentum relative to more traditional feedstocks (e.g. sugar cane) due to potential advantages in terms of sustainability. However game-changing engineering of algae-to-fuel technology, for example in the design of optimised cultivation bioreactors that are really competitive with established fuels, requires a much better rheological understanding and characterisation of algae suspensions. Because in so-called 'active' suspensions swimming microalgae are able to self-propel using flagella, their interaction with flow fields is far more complex than that of non-motile particles, presenting both an opportunity and a challenge. Exploiting swimming activity could lead, for example, to novel separation and 'steering' methods. Nevertheless despite the recognised potential of novel individual and collective behaviour of swimmers for process engineering, experimental studies on algae suspension rheology remain limited and still present basic puzzles. This project's aim is to improve significantly our knowledge and understanding of the flow behaviour of swimming algae in complex flow conditions, in particular in oscillatory flows, mixed shear-extension flows and flows in non-Newtonian media such as viscoelastic suspensions. For this purpose, a type of unicellular algae, Dunaliella Salina, will be examined to determine its swimming capabilities under differing stimuli. The work will be primarily experimentally based, with rheology, microscopy and velocimetry methods as a platform to map out the algae's response. We will use key parameters from the experimental data to go on to inform new models of 'microswimmer' transport and diffusion in complex media, through collaboration with modelling and theory experts.