Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 13, Issue 15, Pages 18175-18183Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c03999
Keywords
hydrogel actuators; near-infrared; Fe3+/tannic acid; photothermal transducer; biomimetic devices
Funding
- Natural Science Foundation of Guangdong Province [2018A030313454]
- National Natural Science Foundation of China [81974322]
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The study introduces a novel NIR-responsive hydrogel actuator incorporating Fe3+/TA, demonstrating enhanced mechanical properties and photothermal effect. Under NIR irradiation, Fe3+/TA within the hydrogel converts light energy into heat, causing the hydrogel to bend upward in the heated region with excellent repeatability.
Light-driven hydrogel actuators show potential applications because their spatiotemporal precision and contact-free manner, especially for near-infrared light (NIR), can be focused on a specific area, which possesses tunable intensity and strong penetrability. Herein, we propose a novel NIR-responsive hydrogel actuator incorporating Fe3+/tannic acid (Fe3+/TA) as a photothermal transducer into the poly(N-isopropylacrylamide) (PNIPAAm) hydrogel via photo-cross-linking and subsequent immersion in FeCl3 solution. TA contains abundant pyrogallol and catechol groups, which can be linked to PNIPAAm through hydrogen bonds during in situ polymerization; moreover, as a mediator, TA can form metal-phenolic networks with Fe3+ via the coordination between catechol and metal ions, endowing the PNIPAAm gel with enhanced mechanical properties as well as NIRresponsive photothermal effect. We demonstrated that introduction of Fe3+/TA maintained the volume phase transition temperature of the hydrogel around 32 degrees C and guaranteed its deformation behaviors upon NIR irradiation. Furthermore, a higher concentration level of BIS and Fe3+ were verified to facilitate a stronger photothermal capacity of the hydrogels. Therefore, under NIR irradiation, Fe3+/TA within the hydrogel converted NIR light into heat, and the local high temperature in the irradiated region would cause the petals of the snowflake-shaped hydrogel to bend upward perpendicular to the horizontal plane within 1 min, possessing excellent repeatability. This study puts forward a new idea of preparing NIR-responsive hydrogel actuators based on Fe3+/TA, which show promising application in the fields of biomimetic devices, flowing control, and soft robotics.
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