Research press release


Nature Communications

Microrobotics: Micro-scallop comes out of its shell



今回、Peer Fischerたちは、2枚のシリコン重合体の殻を1つの蝶番でつないだマイクロ・スキャロップという簡素な微小遊泳体を設計、作製した。それぞれの殻には微小希土類磁石が取り付けられており、外部磁場をかけて磁石と相互作用させることで、それぞれの殻を動かしている。マイクロ・スキャロップは、素早く殻を開いてからゆっくりと殻を閉じたり、あるいはゆっくりと殻を開いてから素早く殻を閉じたりすることによって、2枚の殻の間の液体の粘度を突然変化させることで、正味の推進力を得る。Fischerたちは、この機構が、生体液中で用いる人工の微小遊泳体を設計する際の一般的な仕組みになるのではないかと考えている。

An artificial micro-swimmer, called “micro-scallop”, which can swim through viscous fluids by opening and closing its shells at different rates, is reported this week in Nature Communications. The device represents the first experimental demonstration of swimming by reciprocal motion (the repetitive opening and closing of the scallop shell), and could potentially simplify the production of micro-swimmers that can navigate biomedical fluids and tissues.

Micro-swimmers have the potential to be used for various biomedical tasks, such as drug delivery, and as diagnostic probes. However, most biological fluids are non-Newtonian, meaning that their viscosity varies in response to stress. Designing devices that swim through these fluids is a challenge. Devices inspired by the rotatory motion of flagella in bacteria have generally been used to propel artificial micro-swimmers in biological fluids, however, their motors are complex.

Peer Fischer and colleagues design and fabricate a simple micro-swimmer consisting of two silicone polymer shells connected by a single hinge, called micro-scallop. An external magnetic field is used to drive the movement of each shell by interacting with rare earth micro-magnets attached to each. Fast-opening followed by slow-closing, or vice versa, generates a sudden change in the viscosity of the fluid between the two shells leading to net propulsion by the micro-scallop. The authors suggest that this mechanism may provide a general scheme for designing artificial micro-swimmers for use in biological fluids.

doi: 10.1038/ncomms6119

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