Recently, journal Advanced Materials published the lasted advances in liquid crystalline network materials entitled as “Near-infrared Photodriven Self-sustained Oscillation of Liquid Crystalline Network Film with Predesignated Polydopamine Coating” reported by Professor Huai Yang’s group from College of Engineering, Peking University.
Sustained oscillations, such as wing-beating of flying species and heartbeat of animals, play an important role in living organisms. Diverse self-propelled oscillating systems fueled by continuous stimulations have been fabricated based on emerging soft active materials including hydrogels, polymers and vesicles. However, to realize the remote control of the oscillation materials, most of these systems have to be driven by polarized light or harmful Ultraviolet light. Developing novel materials that can perform macroscopic oscillation fueled by NIR-light is highly demanded but challenging.
Inspired by the biological system in nature, Huai Yang’s group judiciously designed and fabricated by selectively coating a mussel-inspired polydopamine (PDA) polymer layer on the surface of the splay-aligned liquid crystalline network (LCN) film. By selectively coating the PDA layer of the LCN film, the near-infrared light-driven oscillation of the LCN film was obtained because of the photothermal effect from PDA coating and self-blocking effect of the polymer matrix. As shown in Figure 1.
Figure 1. The oscillation behavior of the PDA-coated LCN film.
The oscillating motions of the LCN oscillators can be facilely manipulated by tuning light intensity and film thickness (Figure 2a and 2b). More importantly, the programmability of the PDA coating enables the oscillating behaviors of LCN film to be predesignated and finely adjusted by coating the film with PDA locally and repeatably. It overcomes the shortcomings of the conventional LCN actuators that the modification of the materials has to be operated at the very beginning of the preparation, providing a greener strategy in fabrication of functional LCN oscillators. The programmability of the PDA-coated LCN film was presented in Figure 2c-f.
Figure 2. a, b The influence of the light intensity on the oscillation amplitude and frequency. c, d, e, f The programmability of the LCN actuator.
Owing to over 50 % NIR irradiation in solar spectrum, PDA-coated film was found to oscillate upon exposure of focused sunlight. A novel solar power generation device was designed and fabricated. It proves that the novel sunlight-driven oscillator is capable to motivate the power generation device, successfully transferring the solar energy to electricity (Figure 3). This work provides a versatile strategy to fabricate NIR-light-actuated polymeric oscillators, providing inspirations in the development of biological soft robots and advanced biomimetic devices.
Figure 3. The solar power generation device driven by LCN oscillator.
PhD candidate Mr. Ruochen Lan is the first author of this work. Professor Huai Yang is the only corresponding author of the paper. This work is supported by the National Key R&D Program of China (Grant Nos. 2018YFB0703704) and National Natural Science Foundation of China (Grant Nos. 51573006, 51973155, 51561135014 and 51720105002).