Superfast fuel-free tubular hydrophobic micromotors powered by ultrasound

Versatile micro/nanomotors hold remarkable potentials in medical interventions, environmental remediation and cell engineering, etc. However, limited lifetime and weak locomotion prohibit such micromachines away from most practical applications where fast propulsion without chemical fuels is extremely required. Hereby, we introduce a tubular hydrophobic micromotor activated by ultrasonic power to swim at a superfast speed. The proposed tubular micromotor incorporates one hydrophobic layer inside and captures air bubbles as immersed into liquid surroundings. Once applied with the ultrasound at a reasonable frequency, the trapped bubble vibrates to create intensified local streaming, thereby powering the micromotor to swim spontaneously. To achieve high throughput fabrication, template-assisted electrochemical deposition is utilized for constructing the basic multiple-layer tubular configuration of PEDOT-SiO2 micromotors, followed by one step of hydrophobic treatment to modify the inner structure wettability. Tested results illustrate that the micromotor swims at a speed of up to 11 mm/s, which is equivalent to 1100 times of the body length per second. Additionally, motilities in different fluid environments are compared and interesting interactions between micromotor individuals and other neighbored elements are experimentally discussed. Driven by oscillated microbubbles, the fuel-free hydrophobic micromotors exhibit unique potentials to accomplish superfast swimming for myriad biological applications.