Tough and Multifunctional Composite Film Actuators Based on Cellulose Nanofibers toward Smart Wearables

Abstract

Although humidity-responsive actuators serve as a promising candidate in smart wearables, artificial muscles, and biomimetic devices, most of them derived from synthetic polymers could not simultaneously achieve multifunctional properties. In this work, a cellulose nanofiber (CNF)-based film actuator with high mechanical properties, excellent Joule heating, and antibacterial capability is successfully constructed by integrating with Ti3C2T x (MXene) and tannic acid (TA) via a vacuum-assisted filtration approach. Owing to the unique nacrelike structure and strong hydrogen bonds, the tensile strength and toughness of the composite film could reach 275.4 MPa and 10.2 MJ·m–3, respectively. Importantly, the hydrophilic nature of CNFs and alterable interlayer spacing of MXene nanosheets endow the composite film with sensitive humidity response and extraordinary stability (1000 cycles). With the assistance of MXene nanosheets and TA, the composite film could not only present outstanding Joule heating but also possess remarkable antibacterial properties against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Benefiting from the above merits, the proof-of-concept smart garment is assembled by the as-prepared film and is capable of regulating humidity and temperature.

Cellulose‐Based Soft Actuators

“…[124] The actuator achieved a short response/recovery time (0.8/2 s), a large actuation amplitude (180°), and excellent repeatability (over 1000 cycles without noticeable fatigue). Furthermore, it exhibits a [33] Copyright 2021, American Chemical Society; g) Schematic representation of the four HEPAs and of their motion of actuation; h)Time-lapse photographs of the same precurved HEPA operated at RH = 15% (left) and at RH = 85% (right). Reproduced with permission.…”

“…For instance, Wei and coworkers reported an extremely facile and feasible vacuum‐assisted assembly strategy to design humidity‐responsive composite film actuators assembled by 1D CNF filaments and 2D MXene nanosheets with natural tannic acid (TA) as a cross‐linker ( Figure a). [ 33 ] The composite film actuator acts as the flaps and is embedded in the black cotton sportswear with a circular pattern slightly larger than the diameter of the film. It can open up automatically as skin surface humidity rises and close as humidity falls (Figure 10b).…”

“…Reproduced with permission. [ 33 ] Copyright 2021, American Chemical Society; g) Schematic representation of the four HEPAs and of their motion of actuation; h)Time‐lapse photographs of the same precurved HEPA operated at RH = 15% (left) and at RH = 85% (right). Reproduced with permission.…”

“…f) Water vapor transmission rate test of actuator-based sportswear and normal cotton sportswear. Reproduced with permission [33]. Copyright 2021, American Chemical Society; g) Schematic representation of the four HEPAs and of their motion of actuation; h)Time-lapse photographs of the same precurved HEPA operated at RH = 15% (left) and at RH = 85% (right).…”

“…[30,31,32] For instance, Shao and coworkers integrated MXene and tannic acid into a cellulose nanofiber matrix to develop a composite film actuator that exhibits quick response to humidity, customizable mechanical properties, and efficient Joule heating and antibacterial capability. [33] Thanks to numerous favorable advantages, cellulose-based soft actuators are promising candidates in many applications such as wearable devices, [27] haptics, [34] biomedical field. [35] Moreover, soft actuators play a crucial role in the development of soft robotics, a key component of the current fourth industrial revolution.…”