Prof. Takuzo Aida’s group from The University of Tokyo made unprecedented achievement on actuator and publisher their work on Nature Materials.
Toward a sustainable society, it is important to harness energy from natural resources such as light, heat, and wind power. Hence, during the last few decades, we have intensively developed various energy converters, as represented by organic photovoltaic cells. On the other hand, certain watches function mostly by converting sweeps of human arms (kinetic energy) into electrical energy. Such an energy harvesting technology, which makes use of energy gaps temporarily generated under ambient conditions for operating small mechanical devices on the spot, is also now recognized as very important for realizing a sustainable society.
In the present work, we have reported an unprecedented type of thin-film actuator that seemingly operates autonomously under ambient conditions. In reality, the actuation is driven by undetectably small fluctuations in the ambient humidity. Furthermore, the actuator film can easily jump high or hit a glass bead upon abrupt heating and partial protection of the actuator film against water adsorption enables its unidirectional walking. Although there have been various types of actuators so far developed, none of them exhibit response to such minute humidity fluctuations. The key for these anomalous features of the film is the ultra high-speed and high-sensitive response to water adsorption and desorption of the film. The actuator film consists of a π-stacked carbon nitride polymer (CNP) and the noted properties rely on its mechanical toughness despite its ultra-light weight and ability to bend instantly in response to humidity fluctuations because of its highly anisotropic layered structure of CNPs. The film actuators are available just by one-pot vapor-deposition polymerization (VDP) with a glass substrate using guanidinium carbonate as a starting compound