A flow passage structure is provided with a fluid flow passage that includes a plurality of straight flow passages, a first return bend that connects the downstream end of the straight flow passage through which a fluid flows from a second end surface toward a first end surface among the plurality of straight flow passages to the upstream end of the straight flow passage which is disposed at the downstream side of the straight flow passage and is adjacent to the straight flow passage, and a second return bend that connects the downstream end of the straight flow passage through which the fluid flows from the first end surface toward the second end surface among the plurality of straight flow passages to the upstream end of the straight flow passage which is disposed at the downstream side of the straight flow passage and is adjacent to the straight flow passage.

A microfluidics-based nanoparticle synthesis system, a device and a synthesis method thereof are provided. The nanoparticle synthesis system comprises: a microfluidic chip; a reagent bottle which is connected with the microfluidic chip; and a flow control assembly comprising a pressure controller which is used for controlling the pressure in the reagent bottle. The system achieves high-accuracy flow control, and a microfluidic chip that can achieve high-efficiency and rapid mixing is also used in combination to finally achieve high-throughput and high-uniformity nanoparticle synthesis. A user may adjust the same instrument as required to achieve different throughputs without redesigning the instrument.