At present, environmentally friendly biobased flexible films are of particular interest as next-generation fireproof packaging and sensor materials. To reduce the moisture uptake and fire risks induced by hygroscopic and flammable biobased films, we report a simple and green approach to develop a hydrophobic, flame-retardant composite film with synergetic benefit from soy protein isolate (SPI), sisal cellulose microcrystals (MSF-g-COOH), graphene nanosheets (GN), and citric acid (CA). Compared with SPI/MSF-g-COOH composite films, the as-prepared SPI/MSF-g-COOH/CA/GN composite films have significantly improved water resistance and can maintain excellent physical structure and good electrical conductivity in an ethanol flame. This work opens a pathway for the development of novel fire-retardant fire alarm biosensors.

Low-cost and flexible biofilm humidity sensors with good wet strength are crucial for humidity detection. However, it remains a great challenge to integrate good reversibility, rapid humidity response, and robust humid mechanical strength in one sensor. In this respect, we report a facile method to prepare a sustainable biofilm (named MC film) from sisal cellulose microcrystals (MSF-g-COOH) and citric acid (CA). After crosslinking with CA, the MC film exhibits excellent wet strength and rapid humidity response. More importantly, MC film can be used over a wide temperature range with excellent durability and reversibility for humidity detection. A highly sensitive humidity sensor fabricated from the MC film exhibits high reversibility and excellent water resistance and can be applied in humidity and personalized breath health monitoring. Our work fills the gap between biomaterial design and high-performance sensing devices.

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As a two-dimensional material, graphene has attracted increasing attention as heat dissipation material owing to its excellent thermal transport property. In this work, we fabricated sisal nanocrystalline cellulose/functionalized graphene papers (NPGs) with high thermal conductivity by vacuum-assisted self-assembly method. The papers exhibit in-plane thermal conductivity as high as 21.05 W m−1 K−1 with a thermal conductivity enhancement of 403% from the pure cellulose paper. The good thermal transport properties of NPGs are attributed to the strong hydrogen-bonding interaction between nanocrystalline cellulose and functionalized graphene and the well alignment structure of NPGs.

Early warning sensors rapidly monitor critical temperatures, humidity, and fires, which are crucial to reduce or avoid natural disasters in complex environments, such as fire or water disasters. Here, a highly sensitive, readable, and dual‐functional sensor is designed for a fast‐response fire alarm and rapid humidity detection based on sustainable biological films (named MSCG films). The MSCG films are composed of grafted sisal nanofibers (MgC), silk nanofibers, graphene, and citric acid (CA). After crosslinking with CA, MSCG films exhibit good wet strength (i.e., 128.8 MPa) after soaking in 100 °C water, thus confirming that the films would be applicable to a broad temperature range in humid environments. After flame ignition, the MSCG films are rapidly carbonized to activate an alarm sound and a light in the circuit with a fire response time as short as 1 s. It exhibits ultrafast temperature response/recovery time (i.e., 0.1 s/0.3 s) and rapid humidity response time (i.e., 0.9 s). The dual‐functional sensor is further assembled into a versatile sensor system for real‐time monitoring of fire accidents and environmental humidity, which can be integrated into consumer electronics, such as portable laptops and mobile phones.

Electrospinning preparation of perylene-bisimide-functionalized graphene/polylactic acid composite films with shape-memory properties.

In this work, a kind of nanocomposite paper was obtained by evaporation-induced self-assembly of a mixture of sisal cellulose nanofibers (CNF) and polyethylene glycol (PEG) as the matrix and citric acid (CA) as a cross-linking agent. The CNF/PEG/CA paper exhibited good water swelling resistance which could be controlled by changing the concentration of CA. In addition, this nanocomposite paper exhibited good mechanical properties and water-induced shape memory performance. In particular, when the dosage of CA was 30 wt.%, the tensile strength and the tensile modulus of the CNF/PEG/CA paper after swelling were 25.2 MPa and 813.0 MPa, respectively. Further, this nanocomposite showed great potential for water-induced shape memory materials with fast response speed. The shape recovery rate (Rr) of the CNF/PEG/CA paper reached 90.2% with 30 wt.% CA after being immersed in water for 11 s. It is anticipated that our current work can be used to exploit more efficient methods to overcome the poor water swelling resistance of the cellulose-based shape memory materials.