An Acoustically Controlled Microrobot Modelled on Spirochete Bacteria

As a next-generation toolkit, microrobots can transform a wide range of fields, including micromanufacturing, electronics, microfluidics, tissue engineering, and medicine. While still in their infancy, acoustically actuated wireless microrobots are becoming increasingly attractive, as acoustic control can generate large propulsive forces, requires relatively simple microrobot design, and does not entail complex manipulation systems. However, the interaction of acoustics with microstructure geometry is poorly understood to date, and its study is necessary for developing next-generation acoustically powered microrobots. We present here a mass-manufactured acoustically driven helical microrobot capable of locomotion using a fin-like double-helix microstructure. This microrobot responds to sound stimuli and mimics the spiral motion of natural microswimmers such as spirochetes. The asymmetric double helix interacts with the incident acoustic field, inducing a propulsion torque that causes the microrobot to rotate around its long axis. Moreover, our microrobot has the unique feature of its directionality being switchable by simply tuning the acoustic frequency. We demonstrate this locomotion in 2D and 3D artificial vasculatures using a single sound source. Since ultrasound is widely used as an imaging modality in clinical settings, our robotic system can integrate seamlessly into practice; thus, our findings could contribute to the development of next-generation smart microrobots. One-Sentence SummaryWe present an acoustically driven helical microrobot capable of corkscrew-like locomotion using a double-helix microstructure.