Robust grasshopper-inspired millirobot operates at low voltages

Because of their small size, millirobots are developed for biomedical applications like tissue scaffold construction, cell manipulation and characterization, drug delivery and targeted therapy, and minimally invasive surgery.

Millirobots need to adapt to their working environment and work smoothly with attached sensors and power supplies. Current devices based on dielectric elastomers require high actuation voltages, hindering their power supply integration. Thin piezoelectric polymer film-based millirobots can be driven in relatively low voltages but are not robust and cannot carry the weight of electronics.

Gao et al. developed a bio-inspired biomorph-structured millirobot that can carry nearly 100 times its own weight and operates at voltages two orders of magnitude smaller than dielectric elastomer millirobots.

The millirobot design is based on a grasshopper, with two ferroelectric crystals as piezoelectric layers, and polyethylene terephthalate films as interlayers and feet.

“The top and bottom crystal layers simultaneously elongate or contract within one cycle, which stimulates the designed bending deformation of the grasshopper body,” said author Xiangyu Gao.

The team demonstrated their millirobot’s robustness by carrying various loads, moving on tilted angle plane, and turning around. The device can move at temperatures near -150 degrees C and is partially transparent.

In the future, the researchers plan to explore self-powering options for the millirobot and how groups of millirobots can be used together.

“We think that the idea presented in this work could benefit the design of numerous electromechanical devices,” said Gao.

Source: “A robust, low-voltage driven millirobot based on transparent ferroelectric crystals,” by Xiangyu Gao, Liao Qiao, Chaorui Qiu, Ting Wang, Lin Zhang, Jinfeng Liu, Shuai Yang, Haonan Jin, Benjian Xin, Shujun Zhang, Shuxiang Dong, Zhuo Xu, and Fei Li, Applied Physics Letters (2022). The article can be accessed at https://doi.org/10.1063/5.0079737 .