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We report on robust silk fibroin (SF) gels fabricated by incorporating cellulose nanocrystals (SF/CNC) as a "tough" unit and photopolymerization of acrylamide as an "elastic" segment. The addition of CNC affects the refolding process of SF molecules controlled by nucleation via templating, resulting in a stable mesoscopic structure. The gel shows robust mechanical stability (88.8% of initial stress after 1000 compression cycles) and excellent adhesion to various materials. The connected gel can recover its ionic conductivity within 20 s and be stretched to a maximum strain of 498% after healing for 10 h with an efficiency of 95.2%. This multifunctional gel sensor can sensitively detect different toxic gases and small-scale and large-scale human motions in real-time. Its sensitivity is calculated as GF = 3.84 at 0-200% strain. Especially, the gel with 5 wt % thermochromic pigments as a visual temperature indicator can quickly reflect abnormal human body temperature according to the color change. Therefore, the strategy shows potential applications in flexible electrodes, biomimetic sensors, and visual biosensors.

Flexible wearable electronics were developed for applications such as electronic skins, human-machine interactions, healthcare monitoring, and anti-infection therapy. But conventional materials showed impermeability, single sensing ability, and no designated therapy, which hindered their applications. Thus it was still a great challenge to develop electronic devices with multifunctional sensing properties and self-driven anti-infection therapy. Herein, flexible and breathable on-skin electronic devices for multifunctional fabric based sensing and self-driven designated anti-infection therapy were prepared successfully with cellulose nanocrystals/iron(III) ion/polyvinyl alcohol (CNC/Fe3+/PVA) composite. The resultant composite films possessed robust mechanical performances, outstanding conductivity, and distinguished breathability (3.03 kg/(m2·d)), which benefited from the multiple interactions of weak hydrogen bonds and Fe3+ chelation and synergistic effects among CNC, polyaniline (PANI), and PVA. Surprisingly, the film could be assembled as a multifunctional sensor to actively monitor real-time physical and infection related signals such as temperature, moisture, pH, NH3, and human movements even at sweat states. More importantly, this multifunctional device could act as a self-driven therapist to eliminate bacterial by the release of Fe3+, which was driven by the damage of metal coordination Fe-O bonds due to the high temperature caused by infection at wound sites. Thus, the composite films had potential versatile applications in electronic skins, smart wound dressings, human-machine interactions, and self-driven anti-infection therapy.

The conventional skin sensor detection of human physiological signals can be an effective method for disease diagnosis and health monitoring, but the poor biocompatibility, low sensitivity and complex design largely limit their applications. Developing natural nanofiller-reinforced composites as strain biosensors is an appealing solution to reduce environmental impacts and overcome technical bottleneck. Herein, a versatile nature skin-inspired composite film as flexible strain biosensor was developed based on cellulose nanocrystals-polyaniline (CNC-PANI) composites by utilizing their percolated conductive network in polyvinyl alcohol (PVA) matrix. The composite electronic skin showed robust mechanical strength (50.62 MPa) and high sensitivity (Gauge Factor = 11.467) with easy water-induced self-healing abilities. Moreover, we investigated the functioning mechanism of percolated network and the sensory behavior determined by CNC nanocomposite alignment. The percolation threshold of CNC-polyaniline (PANI) was determined at 4.278% and 5% CNC-PANI composite film shows the best overall sensing property. It was also discovered that the sensitivity of this type of conductive-filler electronic skin can be divided into two separate regions at different strain range due to its percolated network. With films prepared by dry casting and dip coating, the alignment of CNC-PANI also contributes to this unique change in electrical property. Generally, our results demonstrated the mechanism and tunability of conductive nanofiller-based composite strain biosensors as a potential alternative to commercial synthetic sensors.

The intrinsic intermittence of solar energy raises the necessity for thermal energy storage (TES) systems to balance the contradiction between energy supply and demand energy. This work experimentally provides solid-liquid phase change materials (PCMs) with sufficient storage capacity and discharging rate to offer heating for agriculture products by enhancing heat transfer in phase change fiber composites (PCF). To achieve this, we prepared dipole responsive magnetic/solar-driven PCF composites reinforced with magnetic cellulose nanocrystals hybrids (MCNC). The obtained PCF/MCNC-5% showed excellent magnetic property with a saturation magnetization (MS) value of 1.3 emu/g and effective latent heat phase change enthalpies of 69.2 ± 3.5 J/g - 83.1 ± 4.2 J/g. More importantly, PCF/MCNC-5% showed robust high magnetic to thermal energy storage efficiency of 32.5 % and solar light accelerated energy storage efficiency of 58.5 %. These advantages make the PCF composites promising and more desirable for drying and preservation of the fruits and other agriculture products.

Self-healing conductive hydrogels as artificial skin-like materials hold great potential applications in the fields of artificial intelligence, soft robotics and personal healthcare. However, it remained challenging to construct stimuli-free self-healing biomimetic hydrogels with ultra-stretchability and excellent sensitivity. Herein, polyaniline (PANI) was coated on the surface polycarboxylic multi-branched cellulose nanocrystals (Multi CNC-PANI) via templated polymerization. Afterword, rod-like Multi CNC-PANI served as a dynamic bridge endowed those hydrogels hierarchical structure and dynamic hydrogen bond interactions doped with polyvinyl alcohol (PVA)/borax system. Combined with the dynamic borate ester bonds, the biomimetic nanocomposite hydrogels had high breaking strength (171.52 KPa), ultra-stretchability (1085%), rapid self-healing properties, adhesiveness, decent biocompatibility, and sensitivity. Especially, the hydrogels could keep good self-healing ability both in air and underwater without any stimuli, and the self-healing efficiency could reach up to 99.56% within 120 s. This hydrogel sensor could sensitively detect and distinguish human motions including swallow, fingers, wrist, elbow and knee joints, in real-time. Besides, the self-healed hydrogel gave detective signal with uniform and repeatable sensitivity, which endowed the hydrogels mechanically adaptability and good store stability. Therefore, the strategy may provide unique opportunities in designing biomimetic sensors with skin-like mechanical stretchability, sensitivity and self-healing properties.

In this work, cellulose nanocrystals (CNCs) incorporated with supermagnetic iron oxide nanoparticles (Fe3O4 NPs) as (MCNC) hybrids by the co-precipitation method have developed. High-performance nanocomposite films consisting of poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and MCNC hybrids have prepared through a simple solution casting method. The addition of CNCs in MCNC-5% hybrids improved the surface hydrophilicity of PHBV, and displayed a reduction in water vapor permeability by 68.1 %, compared with pristine PHBV. The results prove that the addition of MCNC hybrids can be acted like a sensor to detect voltage change of the nanocomposites as functions of water vapor. The existence of CNCs in the MCNC-5% hybrids caused an increase in tensile strength and Young’s modulus by 74.6 % and 120.2 %, respectively. The addition of CNCs could enhance cell-matrix interactions and thus cytocompatibility of PHBV nanocomposites. The PHBV/MCNC-5% exhibited saturation magnetization (Ms) values of 1.5 emu g−1 and displayed almost a regular and operative voltage response signal with real-time monitoring of water vapor. This work provides sustainable smart packaging materials with high sensitivity for water vapor and excellent biocompatibility.

Herein, self-healing multi-branched cellulose nanocrystals/polyvinyl alcohol (MCNC/PVA) composite films with excellent sensitivity to human motions was synthesized by employing MCNC as reinforcing agent, where the potassium chloride (KCl) was added to enhance the conductivity and strain sensitivity of the composite film. There was a synergistic effect between MCNC and PVA, which could promote the slip and recombination of hydrogen bonds, so that the films had robust strength (2.2 times to pure PVA) and high self-healing efficiency (69.54% after 20 min). Especially, the flexible composite film could clearly monitor both large and subtle human motions (finger bending, swallowing, breathing, and insect crawling), and showed larger subtle strain sensitivity (strains