[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Since the last decade, interest in cellulose nanomaterials known as nanocellulose has been growing. Nanocellulose has various applications ranging from composite reinforcement to rheological modifiers. Recently, nanocellulose has been shown to have great potential in flexible printed electronics applications. The property of nanocellulose to form self-standing thermally stable films has been exploited for producing transparent and smooth substrates for printed electronics. However, other than substrates, the field of printed electronics involves the use of inks, various processing methods and the production of flexible electronic devices. This review aims at providing an overview of the use and potential of nanocellulose throughout the printed electronics field.

Use of nanocellulose in printed electronics: a review

Functionalization of cellulose nanocrystals for advanced applications

Advanced electrochemical energy storage devices (EESDs) that can store electrical energy efficiently while being miniature/flexible/wearable/load-bearing are much needed for various applications ranging from flexible/wearable/portable electronics to lightweight electric vehicles/aerospace equipment. Carbon-based fibers hold great promise in the development of these advanced EESDs (e.g., supercapacitors and batteries) due to their being lightweight, high electrical conductivity, excellent mechanical strength, flexibility, and tunable electrochemical performance. This review summarizes the fabrication techniques of carbon-based fibers, especially carbon nanofibers, carbon-nanotube-based fibers, and graphene-based fibers, and various strategies for improving their mechanical, electrical, and electrochemical performance. The design, assembly, and potential applications of advanced EESDs from these carbon-based fibers are highlighted. Finally, the challenges and future opportunities of carbon-based fibers for advanced EESDs are discussed.

Carbon-Based Fibers for Advanced Electrochemical Energy Storage Devices

Flexible reduced graphene oxide (rGO) sheets are being considered for applications in portable electrical devices and flexible energy storage systems. However, the poor mechanical properties and electrical conductivities of rGO sheets are limiting factors for the development of such devices. Here we use MXene (M) nanosheets to functionalize graphene oxide platelets through Ti-O-C covalent bonding to obtain MrGO sheets. A MrGO sheet was crosslinked by a conjugated molecule (1-aminopyrene-disuccinimidyl suberate, AD). The incorporation of MXene nanosheets and AD molecules reduces the voids within the graphene sheet and improves the alignment of graphene platelets, resulting in much higher compactness and high toughness. In situ Raman spectroscopy and molecular dynamics simulations reveal the synergistic interfacial interaction mechanisms of Ti-O-C covalent bonding, sliding of MXene nanosheets, and π-π bridging. Furthermore, a supercapacitor based on our super-tough MXene-functionalized graphene sheets provides a combination of energy and power densities that are high for flexible supercapacitors.

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Super-tough MXene-functionalized graphene sheets

Robust, hydrophilic graphene/cellulose nanocrystal fiber-based electrode with high capacitive performance and conductivity

Cellulose nanocrystal/zinc oxide (CNC/ZnO) nanohybrids were prepared through citric acid/hydrochloric acid hydrolysis of commercial microcrystalline cellulose (MCC), and simple precipitation with zinc nitrate aqueous solution [Zn(NO3)2·6H2O] via one-pot green synthesis, in which preparation and modification of CNCs were performed simultaneously and the obtained CNCs with carboxyl groups could act as a stabilizing and supporting agent to anchor ZnO nanoparticles. The influence of the Zn2+ ion concentration on the morphology, microstructure, and properties of the CNC/ZnO nanohybrids was investigated by using Fourier-transform infrared and ultraviolet–visible (UV–Vis) spectroscopy, X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy, and thermogravimetric analysis. According to the UV–Vis and XRD results, well-dispersed ZnO nanoparticles with hexagonal wurtzite structure and smallest average diameter of 42.6 nm were successfully anchored onto the surface of the CNCs. The CNC/ZnO nanohybrid CNC/ZnO-0.5 showed improved thermal stability, high antibacterial activity, and photocatalytic activity for methylene blue (MB) due to strong interaction between the CNCs and ZnO nanoparticles. Compared to CNCs, the thermal degradation onset temperature (T
 0) of the nanohybrids was increased by 23.9 °C, while antibacterial ratios of 100.0 and 100.0 % against viable Escherichia coli and Staphylococcus aureus were achieved. Moreover, 93 % of MB dye was decomposed after UV light irradiation for 100 min.

A facile one-pot route for preparing cellulose nanocrystal/zinc oxide nanohybrids with high antibacterial and photocatalytic activity

With growing interest in flexible and wearable devices, the demand for nature-inspired soft smart materials, especially intelligent hydrogels with multiple perceptions toward external strain and temperatures to mimic the human skin, is on the rise. However, simultaneous achievement of intelligent hydrogels with skin-compatible performances, including good transparency, appropriate mechanical properties, autonomous self-healing ability, multiple mechanical/thermoresponsiveness, and retaining flexibility at subzero temperatures, is still challenging and thus limits their application as skinlike devices. Here, conductive nanocomposite hydrogels (NC gels) were delicately designed and prepared via gelation of oligo(ethylene glycol) methacrylate (OEGMA)-based monomers in a glycerol-water cosolvent, where inorganic clay served as the physical cross-linker and provided conductive ions. The resultant NC gels exhibited good conductivity (∼3.32 × 10-4 S cm-1, akin to biological muscle tissue) and an autonomously self-healing capacity (healing efficiency reached 84.8%). Additionally, such NC gels displayed excellent flexibility and responded well to multiple strain/temperature external stimuli and subtle human motions in a wide temperature range (from -20 to 45 °C). These distinguished properties would endow such NC gels significant applications in fields of biosensors, human-machine interfaces, and soft robotics.

Conductive Self-Healing Nanocomposite Hydrogel Skin Sensors with Antifreezing and Thermoresponsive Properties.

Green nanocomposites containing biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and cellulose nanocrystals/silver (CNC-Ag) nanohybrids were synthesized and their properties were investigated It was found that homogeneously dispersed CNC-Ag could act as bifunctional reinforcements to improve the thermal, mechanical and antibacterial properties of PHBV Compared to pristine PHBV, the tensile strength and the maximum decomposition temperature (Tmax) of the nanocomposite with 10 wt% CNC-Ag were enhanced by 140% and 242 °C, respectively The nanocomposites displayed reduced water uptake and water vapor permeability along with lower migration level in both non-polar and polar simulants compared to the neat biopolymer, which can be related to the increased crystallinity and improved interfacial adhesion Moreover, the nanocomposites showed strong antibacterial activity against both Gram-negative E coli and Gram-positive S aureus The results of the study indicate that the high performance nanocomposites show great potential applications in the fields of food, beverage packaging and disposable overwrap films

Reinforcement of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with cellulose nanocrystal/silver nanohybrids as bifunctional nanofillers

Fibers have played a critical role in the long history of human development. They are the basic building blocks of textiles. Synthetic fibers not only make clothes stronger and more durable, but are also customizable and cheaper. The growth of miniature and wearable electronics has promoted the development of smart and multifunctional fibers. Particularly, the incorporation of functional semiconductors and electroactive materials in fibers has opened up the field of fiber electronics. The energy supply system is the key branch for fiber electronics. Herein, after a brief introduction on the history of smart and functional fibers, we review the current state of advanced functional fibers for their application in energy conversion and storage, focusing on nanogenerators, solar cells, supercapacitors and batteries. Subsequently, the importance of the integration of fiber-shaped energy conversion and storage devices via smart structure design is discussed. Finally, the challenges and future direction in this field are highlighted. Through this review, we hope to inspire scientists with different research backgrounds to enter this multi-disciplinary field to promote its prosperity and development and usher in a truly new era of smart fibers.

Guoyin Chen

Papers

Robust, hydrophilic graphene/cellulose nanocrystal fiber-based electrode with high capacitive performance and conductivity

A facile one-pot route for preparing cellulose nanocrystal/zinc oxide nanohybrids with high antibacterial and photocatalytic activity

Conductive Self-Healing Nanocomposite Hydrogel Skin Sensors with Antifreezing and Thermoresponsive Properties.

Reinforcement of biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with cellulose nanocrystal/silver nanohybrids as bifunctional nanofillers

Smart fibers for energy conversion and storage