Reconfigurable Acoustofluidic Microvortices for Selective Microcargo Delivery.

Microscale cargo delivery systems improve precise therapies by enabling delivery of microscale payloads deep into anatomical cavities through complex microvascular networks. Traditional methods face challenges, such as slow infusion, low payload throughput, and poor selectivity at microchannel bifurcations. Inspired by rotifers' adaptive predation, we introduce reconfigurable microvortex generators (r-MVGs) featuring a frequency-encoded acoustofluidic actuation mechanism, which can dynamically switch multiple modes under a single tunable ultrasound field. Diverging from conventional single-mode microvortex or magnetic systems, the present approach leverages pairwise microbubble resonance encoding. This mechanism, wherein microbubbles of discrete sizes resonate at distinct acoustic frequencies, enables controlled attraction-repulsion transitions and programmable microvortex reconfiguration. These acoustically driven micromachines include a programmable active component and a passive nozzle connected by a rotary hinge controlled by paired microbubbles, creating directed microvortices. Simulations and experiments show that each bubble pair defines a unique frequency band, enabling multiple, independently tunable reconfigurable modes and real-time switching between capture, release, and directional delivery. Using this platform, we successfully achieved selective payload guidance through a trifurcated microchannel network via active flow control. This frequency-encoded r-MVG system thus establishes a new paradigm for adaptive, multimodal, and high-throughput acoustofluidic delivery in microfluidics, biomedicine, advanced manufacturing, and nano-reservoir exploration.