BIOMICAR · Biological Microswimmers for Cargo Delivery Systems: Modelling, Simulations and Experiments

Biological Microswimmers for Cargo Delivery Systems: Modelling, Simulations and Experiments

Self-propelled microorganisms such as bacteria, protozoa, and microalgae—referred to as biological microswimmers (BM)—play a fundamental role in natural and engineered systems. In nature, their individual and collective dynamics underpin key processes, including the regulation of carbon and oxygen biogeochemical cycles, the structuring of microbial ecosystems, and the emergence of harmful phenomena such as toxin release during phytoplankton blooms under specific environmental conditions. Beyond their ecological relevance, BM have attracted growing interest as functional agents for technological and biomedical applications, particularly as autonomous carriers capable of transporting and releasing microscopic cargoes. A central challenge limiting the translation of these concepts into reliable applications is the lack of precise control over the collective motion of BM. While proof-of-principle studies have demonstrated the feasibility of using BM as transporters, their delivery efficiency remains low. This limitation stems from the intrinsic complexity of real-world environments, where BM swim through confined and porous media, interact with each other and with passive and active agents, and respond to multiple external fields, such as light gradients, chemical cues, and background fluid flows. These factors strongly influence microswimmer trajectories, induce collective behaviors, and significantly reduce the predictability and controllability of their motion. Current theoretical, computational, and experimental approaches typically address these influences in isolation. To date, the combined and concomitant effects of confinement, external fields, and multi-agent interactions on BM dynamics have not been systematically integrated into simulation frameworks or experimental designs. This fragmentation limits our ability to understand and predict emergent collective behaviors and, critically, to exploit them for targeted transport and delivery. Addressing this gap is essential to advancing both fundamental active-matter science and the conceptual design of efficient BM-based cargo-delivery systems. The overarching objective of this project is to establish a comprehensive, predictive framework for the collective dynamics of interacting biological microswimmers in complex, confined environments under external stimuli. To achieve this, the project will develop a computational platform capable of simulating suspensions of interacting BM subjected simultaneously to geometric confinement, external fields (such as light, gravity, and chemical gradients), and interactions with other active or passive agents. This platform will enable systematic exploration of how these factors jointly shape collective motion, synchronization, and transport efficiency. A key element of the project pathway to impact is the tight integration between simulations and experiments. Computational predictions will be continuously tested and refined through microfluidic experiments on suspensions of phototactic microalgae (Chlamydomonas reinhardtii) mixed with passive colloids. This feedback loop will ensure physical realism, validate model assumptions, and accelerate the identification of robust control strategies. By providing quantitative insight into how collective BM behavior can be steered toward desired targets, the project is expected to contribute significantly to the rational design of BM-based delivery systems. At a broader scale, the results will advance the understanding of active matter in realistic environments, with implications for environmental sciences, micro-robotics, and bio-inspired engineering. The anticipated impact spans from improved predictive models of microbial transport in natural porous media to foundational knowledge enabling future applications in targeted delivery and microscale manipulation.

Data: CORDIS, © European Union