Materials that respond instantly and reversibly to external stimuli are optimal choices as actuators to be applied in real-world applications currently. However, to make an actuator that produce sustained response without fatigue remains challenging.

Researcher ZHANG Lidong and Professor DU Xuemin from Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, developed bio-inspired actuators that can produce fatigueless, long-term motion. These programmable actuators fabricated as single- or bilayer elements can reversibly respond to minute concentrations of acetone vapors.

By using templates, microchannel structures are replicated onto the surface of two highly elastic polymers, polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA), to induce chiral coiling upon exposure to acetone vapors. The vapomechanical coiling is reversible and can be conducted repeatedly over one hundred times without apparent fatigue.

Moreover, the actuator composed of a single PVDF layer maintains its ability to move over an acetone-soaked filter paper even after several days. The controllable and reproducible sensing capability of this smart material could be utilized for actuating dynamic elements in soft robotics.

The paper “Vapomechanically Responsive Motion of Microchannel-Programmed Actuators” was published in the Advanced Materials on July 31, 2017. This research work is supported by the National Natural Science Foundation, Guangdong innovative and entrepreneurial research team program and Shenzhen peacock plan.

Figure 1. Closing up and blooming with ad/desorption of acetone vapors (Image by DU Xuemin) 

Figure 2. Film size of bio-inspired actuators (Image by DU Xuemin) 

Figure 3.  Vapomechanically responsive motion of microchannel-programmed actuators (Image by DU Xuemin)