An autonomous actuator driven by fluctuations in ambient humidity

Abstract

Devices that respond to negligibly small fluctuations in environmental conditions will be of great value for the realization of more sustainable, low-power-consumption actuators and electronic systems. Herein we report an unprecedented film actuator that seemingly operates autonomously, because it responds to the adsorption and desorption of a minute amount of water (several hundred nanograms per 10 mm(2)) possibly induced by fluctuations in the ambient humidity. The actuation is extremely rapid (50 ms for one curl) and can be repeated >10,000 times without deterioration. On heating or light irradiation, the film loses adsorbed water and bends quickly, so that it can jump vertically up to 10 mm from a surface or hit a glass bead. The film consists of a π-stacked carbon nitride polymer, formed by one-pot vapour-deposition polymerization of guanidinium carbonate, and is characterized by a tough, ultralightweight and highly anisotropic layered structure. An actuator partially protected against water adsorption is also shown to walk unidirectionally.

Research Progress of Solvent-based Smart Actuator Materials

“…(B)多孔膜与实心膜响应程度的比较 [56] . (C)各向异性层状结构的 CNP 膜驱动原理示意图 [54] Figure 4 Ion concentration/pore structure gradient distribution. (A) Actuation mechanism via solvent molecule sorption, the structural gradient along the membrane cross-section (top-down direction) [68] .…”

“…(B) A schematic mechanism of the sensitive actuation of a porous membrane actuator (left) compared to dense one (right) [56] . (C) Scheme of anisotropic layered structures for actuating motions of a CNP film [54] 化 学 学 报 Figure 5 External stimulus gradient distribution. (A) Schematic illustration of the mechanical locomotion mechanism of the uniform RGO-PDA thin film actuator.…”

“…(C) Sketch of a device for humidity-to-electricity conversion [53] . (D) The evaporation-driven oscillatory engine [93] 题组在具有湿度响应的琼脂糖上排列不同取向的玻璃 纤维, 制备出能调控弯曲方向的湿度响应驱动器 [53] (图 6C [54] . (B)环境湿度驱动下的自行走行为 [94] .…”

“…(A) Unidirectional walking of a partially protected CNP film driven by fluctuations in ambient humidity [54] . (B) Self-walking of the device on the ratchet substrate driven by changing the environmental humidity [94] .…”

Designing dynamic functional molecular systems

“…4). 22 These films curled and straightened in response to small changes in ambient humidity. At constant humidity, deviations in temperature affected the desorption and adsorption of water which in turn resulted in the movement of the film.…”