With the increasing demand for wearable electronics (such as smartwatch equipment, wearable health monitoring systems, and human–robot interface units), flexible energy storage systems with ...eco‐friendly, low‐cost, multifunctional characteristics, and high electrochemical performances are imperative to be constructed. Nanocellulose with sustainable natural abundance, superb properties, and unique structures has emerged as a promising nanomaterial, which shows significant potential for fabricating functional energy storage systems. This review is intended to provide novel perspectives on the combination of nanocellulose with other electrochemical materials to design and fabricate nanocellulose‐based flexible composites for advanced energy storage devices. First, the unique structural characteristics and properties of nanocellulose are briefly introduced. Second, the structure–property–application relationships of these composites are addressed to optimize their performances from the perspective of processing technologies and micro/nano‐interface structure. Next, the recent specific applications of nanocellulose‐based composites, ranging from flexible lithium‐ion batteries and electrochemical supercapacitors to emerging electrochemical energy storage devices, such as lithium‐sulfur batteries, sodium‐ion batteries, and zinc‐ion batteries, are comprehensively discussed. Finally, the current challenges and future developments in nanocellulose‐based composites for the next generation of flexible energy storage systems are proposed.
Recent advances on nanocellulose‐based composites consisting of nanocellulose and other electrochemical materials for emerging flexible energy‐storage devices are comprehensively discussed, with a focus on structure–property–application relationships to optimize their performance. The current challenges and future developments regarding design and fabrication of nanocellulose‐based composites for the next generation of energy‐storage systems are discussed and proposed.
The recent strategies in preparation of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) were described. CNCs and CNFs are two types of nanocelluloses (NCs), and they possess various ...superior properties, such as large specific surface area, high tensile strength and stiffness, low density, and low thermal expansion coefficient. Due to various applications in biomedical engineering, food, sensor, packaging, and so on, there are many studies conducted on CNCs and CNFs. In this review, various methods of preparation of CNCs and CNFs are summarized, including mechanical, chemical, and biological methods. The methods of pretreatment of cellulose are described in view of the benefits to fibrillation.
Highlights
Preparation strategies of cellulose nanopaper were elaborated.
Functionalization of cellulose nanopaper and its advanced applications were summarized.
Prospects and challenges of cellulose ...nanopaper were discussed.
Cellulose nanopaper has shown great potential in diverse fields including optoelectronic devices, food packaging, biomedical application, and so forth, owing to their various advantages such as good flexibility, tunable light transmittance, high thermal stability, low thermal expansion coefficient, and superior mechanical properties. Herein, recent progress on the fabrication and applications of cellulose nanopaper is summarized and discussed based on the analyses of the latest studies. We begin with a brief introduction of the three types of nanocellulose: cellulose nanocrystals, cellulose nanofibrils and bacterial cellulose, recapitulating their differences in preparation and properties. Then, the main preparation methods of cellulose nanopaper including filtration method and casting method as well as the newly developed technology are systematically elaborated and compared. Furthermore, the advanced applications of cellulose nanopaper including energy storage, electronic devices, water treatment, and high-performance packaging materials were highlighted. Finally, the prospects and ongoing challenges of cellulose nanopaper were summarized.
Highlights
Hyperelastic and superlight multifunctional MXene/nanocellulose composite aerogels with high conductivity are designed by constructing biomimetic texture.
The MXene/nanocellulose aerogels ...as flexible pressure sensors exhibit appealing linear sensitivity performance (817.3 kPa
−1
).
The as-prepared compressible supercapacitor with MXene/nanocellulose electrodes reveals superior electrochemical performance (849.2 mF cm
−2
at 0.8 mA cm
−2
).
Multifunctional architecture with intriguing structural design is highly desired for realizing the promising performances in wearable sensors and flexible energy storage devices. Cellulose nanofiber (CNF) is employed for assisting in building conductive, hyperelastic, and ultralight Ti
3
C
2
T
x
MXene hybrid aerogels with oriented tracheid-like texture. The biomimetic hybrid aerogels are constructed by a facile bidirectional freezing strategy with CNF, carbon nanotube (CNT), and MXene based on synergistic electrostatic interaction and hydrogen bonding. Entangled CNF and CNT “mortars” bonded with MXene “bricks” of the tracheid structure produce good interfacial binding, and superior mechanical strength (up to 80% compressibility and extraordinary fatigue resistance of 1000 cycles at 50% strain). Benefiting from the biomimetic texture, CNF/CNT/MXene aerogel shows ultralow density of 7.48 mg cm
−3
and excellent electrical conductivity (~ 2400 S m
−1
). Used as pressure sensors, such aerogels exhibit appealing sensitivity performance with the linear sensitivity up to 817.3 kPa
−1
, which affords their application in monitoring body surface information and detecting human motion. Furthermore, the aerogels can also act as electrode materials of compressive solid-state supercapacitors that reveal satisfactory electrochemical performance (849.2 mF cm
−2
at 0.8 mA cm
−2
) and superior long cycle compression performance (88% after 10,000 cycles at a compressive strain of 30%).
Discriminative dictionary learning plays a key role in sparse representation-based classification. In this paper, we propose a low-rank graph preserving discriminative dictionary learning (LRGPDDL) ...method for sparse representation-based image recognition. Specifically, we learn a common sub-dictionary as well as several class-specific sub-dictionaries to explicitly capture the common information shared by all the classes and the class-specific information belonging to the corresponding class. We also impose a low-rank constraint on each sub-dictionary to weaken the negative influence from noise contained in training samples. A discriminative graph preserving criterion and a discriminative reconstruction error term are used for exploiting discriminative information, which can improve the discriminative ability of the learned dictionary effectively. In addition, an incoherence term is also introduced into the proposed dictionary learning model to encourage the learned sub-dictionaries to be as independent as possible. Experimental results on several image datasets verify the effectiveness and robustness of LRGPDDL.
•A low-rank graph preserving discriminative dictionary learning method is proposed.•A low-rank constraint and an incoherence term are introduced in the DL model.•A discriminative graph preserving criterion is incorporated into the DL model.
Cellulose nanopaper (CNP) made of cellulose nanofibrils has gained extensive attention in recent years for its lightweight and superior mechanical properties alongside sustainable and green ...attributes. The mechanical characterization studies on CNP at the moment have generally been limited to tension tests. In fact, thus far there has not been any report on crack initiation and growth behavior, especially under dynamic loading conditions. In this work, crack initiation and growth in self-assembled CNP, made from filtration of CNF suspension, are studied using a full-field optical method. Dynamic crack initiation and growth behaviors and time-resolved fracture parameters are quantified using Digital Image Correlation technique. The challenge associated with dynamic loading of a thin strip of CNP has been overcome by an acrylic holder with a wide pre-cut slot bridged by edge-cracked CNP. The ultrahigh-speed digital photography is implemented to map in-plane deformations during pre- and post-crack initiation regimes including dynamic crack growth. Under stress wave loading conditions, macroscale crack growth occurs at surprisingly high-speed (600–700 m/s) in this microscopically fibrous material. The measured displacement fields from dynamic loading conditions are analyzed to extract stress intensity factors (SIF) and energy release rate (
G
) histories. The results show that the SIF at crack initiation is in the range of 6–7 MPa m
1/2
, far superior to many engineering plastics. Furthermore, the measured values increase during crack propagation under both low- and high-strain rates, demonstrating superior fracture resistance of CNP valuable for many structural applications.
Graphical abstract
Bacterial cellulose (BC) and its derivatives are a rich source of renewable natural ingredients, which are of great significance for biomedical and medical applications but have not yet been fully ...exploited. BC is a high-purity, biocompatible, and versatile biomaterial that can be used alone or in combination with other ingredients such as polymers and nanoparticles to provide different structural organization and function. This review briefly introduces the research status of BC hydrogels, focusing on the preparation of BC-based composite hydrogels and their applications in the field of biomedicine, particularly the wound dressings, tissue engineering scaffolds, and drug delivery.
By reviewing the most recent literature on this subject, we summarized recent advances in the preparation of BC-based composite hydrogels and their advances in biomedical applications, including wound dressings, tissue engineering, and drug delivery.
BC composite hydrogels have broadened the field of application of BC and developed a variety of BC-based biomaterials with excellent properties. BC-based hydrogels have good biocompatibility and broad application prospects in the biomedical field.
BC-based composite hydrogels with the advantages of 3D structure, nontoxicity, high purity, and good biocompatibility, have great prospects in the development of sustainable and multifunctional biomaterials for biomedical applications.
In this work, tension and fracture behaviors of cellulose nanopaper (CNP) made from two different preparation approaches are comparatively studied. The CNP are prepared by casting (or C-CNP) and ...filtration (or F-CNP) of CNF suspension. The resulting CNP are mechanically characterized using the vision-based full-field optical method of Digital Image Correlation. Tension tests show that F-CNP has a higher strength and greater nonlinearity than the C-CNP. The crack initiation and growth characteristics of the two types of CNP are investigated using optical measurements. The data are analyzed under small-scale-yielding conditions to quantify the fracture parameters such as stress intensity factors and energy release rates at crack initiation as well as during crack growth. The results indicate that both C-CNP and F-CNP show significant crack growth resistance in the post-crack initiation regime. The F-CNP particularly offers substantial resistance to crack growth relative to the C-CNP demonstrating that filtration is the preferred method to make CNP with higher tensile strength and better fracture properties.
Graphic abstract
Cross-modality visible-infrared person re-identification (VI-ReID) aims to match visible and infrared images of pedestrians from different cameras. Most existing VI-ReID methods learn global features ...of pedestrians from the original image subspace. However, they are not only susceptible to background clutter, but also do not explicitly handle the discrepancy between the two modalities. In addition, some local-based person re-identification methods extract the local features of pedestrians by slicing pedestrian feature maps. However, most of them simply concatenate these local features to obtain the final local features of pedestrians, ignoring the importance of each of these local features. To this end, we propose a triple-path global–local feature complementary network (TGLFC-Net). Specifically, we introduce intermediate modality images to weaken the impact of modality discrepancy and thus obtain the robust global features of pedestrians. Moreover, we design a local comprehensive discriminative feature mining module, which improves the network’s capability of mining the local comprehensive discriminative features of pedestrians by performing dynamic weighted fusion of local features. Since the final representations of pedestrians incorporate the robust global features and the local comprehensive discriminative features, they have stronger robustness and discriminative capability. In addition, we also design a weighted regularization center triplet loss, which can not only eliminate the negative impact of anomalous triplets, but also reduce the computational complexity of the network. Experimental results on RegDB and SYSU-MM01 datasets demonstrate that TGLFC-Net can achieve a satisfactory VI-ReID performance. In particular, it achieves 92.36% Rank-1 accuracy and 80.32% mAP on the RegDB dataset, respectively.
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