A Multi-engine Marangoni Rotor with Controlled Motion for Mini-Generator Application

Marangoni rotors are smart devices that are capable of self-propulsive motions based on the Marangoni effect, namely interfacial flows caused by a gradient of surface tension. Owing to the features of untethered motions and coupled complexity with fluid, these Marangoni devices are attractive for both theoretical study and applications in biomimicking, cargo delivery, energy conversion, etc. However, the controllability of Marangoni motions dependent on concentration gradients remains to be improved, including the motion lifetime, direction, and trajectories. The challenge lies in the flexible loading and adjustments of surfactant fuels. Herein, we design a multi-engine device in a six-arm shape with multiple fuel positions allowing for motion control and propose a strategy of diluting the surfactant fuel to prolong the motion lifetime. The resulting motion lifetime has been extended from 140 to 360 s by 143% compared with conventional surfactant fuels. The motion trajectories could be facilely adjusted by changing both the fuel number and positions, leading to diverse rotation patterns. By integrating with a coil and a magnet, we obtained a system of mini-generators based on the Marangoni rotor. Compared with the single-engine case, the output of the multi-engine rotor was increased by 2 magnitudes owing to increased kinetic energy. The design of the above Marangoni rotor has addressed the problems of concentration-gradient-driven Marangoni devices and enriched their applications in harvesting energy from the environment.

Automated summary

In this study, a multi-engine six-arm-shaped device was designed, allowing for motion control through multiple fuel positions. A strategy of diluting the surfactant fuel was proposed to prolong the motion lifetime, resulting in an extension of 143% compared to conventional surfactant fuels. The motion trajectories could be easily adjusted by changing the fuel number and positions, leading to diverse rotation patterns. By integrating with a coil and a magnet, a system of mini-generators based on the Marangoni rotor was obtained, with a significantly increased output compared to the single-engine case. The design of the Marangoni rotor addressed the issues of concentration-gradient-driven devices and enriched their applications in energy harvesting from the environment.