Programmable microfluidics for zebrafish larvae manipulation using multiple magnetic microrobots

Microfluidic platforms capable of generating reconfigurable flow environments play an increasingly essential role in zebrafish-based behavioral studies, in which controlled and non-invasive larval transportation is required to ensure reliable assay outcomes. Various magnetically actuated and flow-based systems have demonstrated dynamic modulation of microfluidic flow fields. The realization of spatially reconfigurable and independently addressable hydrodynamic actuation within a unified platform for transport-oriented applications, however, remains technically challenging. To address these limitations, a programmable microfluidic platform was developed by employing multiple magnetic microrobots whose rotational motion was systematically engineered across distinct patterns, including continuous, short-pause intermittent, and long-pause intermittent actuations to enable larval transport. Among these motions, the short-pause intermittent rotation was observed to achieve the fastest transport time of 20 s, corresponding to a 70% and 25% improvement relative to the control and continuous microrobot rotation, respectively. To further elucidate the hydrodynamic mechanisms underlying this enhanced performance, μPIV analysis was conducted to characterize the flow fields generated by the rotational patterns. In addition, the proposed paradigm was compared with its natural food-cue-based counterpart, and it was observed to exhibit a 26.8% higher target-approach efficiency than the food-cue-driven motion. These findings showed that the platform enabled programmable, flow-based larval manipulation and offered a foundation for future microfluidic control strategies.