Researchers at University of New South Wales, Australia, have applied buoyancy-control mechanisms used by An artist's representation of micro-submarines transporting their medical cargo through capillaries among red blood cells. Source: University of New South WalesAn artist's representation of micro-submarines transporting their medical cargo through capillaries among red blood cells. Source: University of New South Walessubmarines to develop self-propelled, micro-machines with a medical mission. The micrometer-sized micromotors are designed as autonomous drug-delivery vehicles that navigate without external control, targeting specific areas of the human body to release pharmaceutical payloads.

Just as submarines use water as ballast to submerge and air to rise, the micromotors effect buoyancy control by emitting or containing gas bubbles in response to ambient biological pH conditions. The devices are composed of composite metal-organic frameworks containing catalase, a bioactive enzyme, as the engine for gas bubble generation. The bubbles produced can be reversibly retained or expelled from the micromotors, leading to buoyancy control.

The buoyancy mechanism could be exploited to steer the drug vehicles toward the acidic environs of cancer cells for precise drug delivery. One capsule could contain millions of these smart drug delivery vehicles, each transporting millions of drug molecules.

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