Biofilms play critical roles in wastewater treatment, bioremediation, and medical-device-related infections. Understanding the dynamics of biofilm formation and growth is essential for controlling and exploiting their properties. However, the majority of current studies have focused on the impact of steady flows on biofilm growth, while flow fluctuations are common in natural and engineered systems such as water pipes and blood vessels. Here, we reveal the effects of flow fluctuations on the development of Pseudomonas putida biofilms through systematic microfluidic experiments and the development of a theoretical model. Our experimental results showed that biofilm growth under fluctuating flow conditions followed three phases: lag, exponential, and fluctuation phases. In contrast, biofilm growth under steady-flow conditions followed four phases: lag, exponential, stationary, and decline phases. Furthermore, we demonstrated that low-frequency flow fluctuations promoted biofilm growth, while high-frequency fluctuations inhibited its development. We attributed the contradictory impacts of flow fluctuations on biofilm growth to the adjustment time (T₀) needed for biofilm to grow after the shear stress changed from high to low. Furthermore, we developed a theoretical model that explains the observed biofilm growth under fluctuating flow conditions. Our insights into the mechanisms underlying biofilm development under fluctuating flows can inform the design of strategies to control biofilm formation in diverse natural and engineered systems.

生物膜在废水处理、生物修复和医疗设备相关感染中发挥着关键作用。了解生物膜形成和生长的动态对于控制和利用其特性至关重要。然而，目前大多数研究都集中在稳定流量对生物膜生长的影响，而流量波动在水管和血管等自然和工程系统中很常见。在这里，我们通过系统的微流体实验和理论模型的发展揭示了流量波动对恶臭假单胞菌生物膜发育的影响。我们的实验结果表明，脉动流条件下生物膜的生长遵循三个阶段：滞后期、指数期和波动期。相比之下，稳定流条件下的生物膜生长遵循四个阶段：滞后期、指数期、稳定期和衰退期。此外，我们证明低频流量波动促进生物膜生长，而高频波动抑制其发展。我们将流量波动对生物膜生长的矛盾影响归因于剪切应力从高到低变化后生物膜生长所需的调整时间（ T _{0 ）。}此外，我们开发了一个理论模型来解释在脉动流量条件下观察到的生物膜生长。我们对波动流量下生物膜形成的机制的深入了解可以为控制不同自然和工程系统中生物膜形成的策略设计提供信息。