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Small-Scale Propellers Deliver Miniature Versions of Themselves.

Small-scale actuators and propellers have benefited from advances in materials and manufacturing to become more lifelike. Inspired by animal species, multi-generational chemically powered artificial propellers that carry small versions of themselves and deliver them "on-the-fly" are described. The released replicas are capable of autonomous propulsion and propelling immediately after detachment. Release occurs without human involvement and relies solely on sacrificial layers separating the carriers and replicas. These layers are composed of transient natural polymers, which dissolve under the swimming conditions to release the confined replicas. Judicious selection of the responsive transient materials, layer thickness, and solution conditions (e.g., pH), leads to programmable delivery of the replicas. Finally, the ability of the same carrier propellers to carry and transport multiple generations of propellers and deliver them at predetermined times is demonstrated.