Finite element analysis of vibration-driven electro-active paper energy harvester with experimental verification

In this research work, a coupled-field finite element model of electro-active paper energy harvester is presented, and the results are verified experimentally. Electro-active paper is a smart form of cellulose coated with electrodes on both sides. A finite element model was developed, and harmonic and transient analyses were performed using a commercial finite element analysis package. Two 80 mm × 50 mm and 100 mm × 50 mm aluminum cantilever benders bonded with electro-active paper were tested to validate the finite element model results. Displacement and voltage generated by the energy harvester at the electrode surfaces were measured. The electro-active paper energy harvesters were excited at their fundamental resonance frequencies by a sinusoidal force located 18 mm from the free end. The voltage obtained from the 80 mm × 50 mm and 100 mm × 50 mm electro-active paper energy harvester finite element model was 3.7 and 7 mV, respectively. Experimental results have shown good agreement with the finite element model. The direct piezoelectric effect of electro-active paper shows potential for a cellulose-based eco-friendly energy harvester

Nanocellulose Bulk Material Prepared by Steam Treatment and Hot Press Molding: Material Processing and Machining Test

Nanocellulose (NC) has been spotlighted as a new building block of future materials since it has many advantages, such as being lightweight and environment-friendly and having high mechanical properties and heat resistance. However, the use of NC requires an upscale manufacturing process to maintain its advantageous properties. Herein, the process of assembling NC into a macro-scale bulk material was developed through a combination of steam treatment and hot press molding. The steam treatment was applied to an NC paste to energize the hydroxyl groups in the cellulose, followed by two stages of hot press molding, which helped in the self-assembly of NC without adhesives. Cellulose nanocrystals were used as the NC, and circular disk shape specimens were prepared. The mechanical properties of the prepared bulk material were higher than typical engineering plastics. In addition, an end mill machining test of the NC bulk material showed its machinability. This paper showed the processing feasibility of NC bulk material, which can substitute plastics

Fabrication Method Study of ZnO Nanocoated Cellulose Film and Its Piezoelectric Property

Recently, a cellulose-based composite material with a thin ZnO nanolayer—namely, ZnO nanocoated cellulose film (ZONCE)—was fabricated to increase its piezoelectric charge constant. However, the fabrication method has limitations to its application in mass production. In this paper, a hydrothermal synthesis method suitable for the mass production of ZONCE (HZONCE) is proposed. A simple hydrothermal synthesis which includes a hydrothermal reaction is used for the production, and the reaction time is controlled. To improve the piezoelectric charge constant, the hydrothermal reaction is conducted twice. HZONCE fabricated by twice-hydrothermal reaction shows approximately 1.6-times improved piezoelectric charge constant compared to HZONCE fabricated by single hydrothermal reaction. Since the fabricated HZONCE has high transparency, dielectric constant, and piezoelectric constant, the proposed method can be applied for continuous mass production

Flexible cellulose and ZnO hybrid nanocomposite and its UV sensing characteristics

This paper reports the synthesis and UV sensing characteristics of a cellulose and ZnO hybrid nanocomposite (CEZOHN) prepared by exploiting the synergetic effects of ZnO functionality and the renewability of cellulose. Vertically aligned ZnO nanorods were grown well on a flexible cellulose film by direct ZnO seeding and hydrothermal growing processes. The ZnO nanorods have the wurtzite structure and an aspect ratio of 9 ~ 11. Photoresponse of the prepared CEZOHN was evaluated by measuring photocurrent under UV illumination. CEZOHN shows bi-directional, linear and fast photoresponse as a function of UV intensity. Electrode materials, light sources, repeatability, durability and flexibility of the prepared CEZOHN were tested and the photocurrent generation mechanism is discussed. The silver nanowire coating used for electrodes on CEZOHN is compatible with a transparent UV sensor. The prepared CEZOHN is flexible, transparent and biocompatible, and hence can be used for flexible and wearable UV sensors

Production of Micro- and Nanofibrillated Cellulose through an Aqueous Counter Collision System Followed by Ultrasound: Effect of Mechanical Pretreatments

The purpose of this work was the production of cellulose micro-nanofibrils from wood pulps through a combination of mechanical treatments, including a recently patented process, a so-called aqueous counter collision (ACC) method followed by ultrasound treatment. Previously to ACC process, the raw pulp materials had to be downscaled to micro-sized dimension, due to the limits of collision jets nozzle diameter. Therefore, the softwood and hardwood pulps were mechanically pre-treated with valley beater refining or dry ball milling. Optical microscopy, atomic force microscopy, X-ray diffraction, thermogravimetric analysis, and gravimetric yield were estimated, to evaluate the effect of mechanical pretreatments on the proposed integrated fibrillation process. The characterizations indicated that valley beater as mechanical pretreatment was found to be more efficient compared to ball milling, of producing cellulose micro-nanofibrils in compliance with the proposed experimental procedure

Tannic-Acid-Cross-Linked and TiO₂-Nanoparticle-Reinforced Chitosan-Based Nanocomposite Film

A chitosan-based nanocomposite film with tannic acid (TA) as a cross-linker and titanium dioxide nanoparticles (TiO2) as a reinforcing agent was developed with a solution casting technique. TA and TiO2 are biocompatible with chitosan, and this paper studied the synergistic effect of the cross-linker and the reinforcing agent. The addition of TA enhanced the ultraviolet blocking and mechanical properties of the chitosan-based nanocomposite film. The reinforcement of TiO2 in chitosan/TA further improved the nanocomposite film’s mechanical properties compared to the neat chitosan or chitosan/TA film. The thermal stability of the chitosan-based nanocomposite film was slightly enhanced, whereas the swelling ratio decreased. Interestingly, its water vapor barrier property was also significantly increased. The developed chitosan-based nanocomposite film showed potent antioxidant activity, and it is promising for active food packaging

Flexible NO2 sensors from renewable cellulose nanocrystals/iron oxide composites

A bio-friendly nanostructured cellulose nanocrystal (CNC) sheet with iron oxide grown on it acting as a nitrogen dioxide (NO2) gas sensor was fabricated by hydrothermal method. The structural investigation was done to monitor the growing mechanism of iron oxide on CNC surface using electron microscope as well as physical and chemical characterization methods. The sensing performance test for NO2 molecules demonstrates that the devices are highly sensitive and fully recoverable at room temperature, which is attributed to the excellent access of nitrogen dioxide molecules to the sensor surface via CNC. The effects of the temperature, durability, and flexibility of sensor are investigated. The reported sensor performance is a huge improvement towards low power consumption and its room temperature operation augurs well for use in various applications.National Research Foundation of Korea (NRF-2013M3C1A3059586).Scopu

Electroactive and Optically Adaptive Bionanocomposite for Reconfigurable Microlens

This paper introduces an electroactive bionanocomposite based on poly(diethylene glycol adipate) (PDEGA) and cellulose nanocrystals (CNCs). The bionanocomposites were made using CNCs extracted from cotton and by optimizing its concentration in terms of the optical transmittance and viscosity. The characteristic properties of the materials were analyzed using contact angle measurements and Fourier transformation infrared spectra. Using the PDEGA/CNC bionanocomposite at a very low concentration of CNCs, a configurable lens having a robust, self-contained tunable optical structure was developed. The shape and curvature of the soft PDEGA/CNC device were controlled by applying voltage, and the focal length was measured. The simple structure, high optical transparency, biodegradability, thermal stability, high durability, and low power consumption make the new material particularly useful in fabricating a reconfigurable lens for future electronic and optical devices. 2016 American Chemical Society.This work was supported by National Research Foundation of K o r e a ( N RF - 2 0 1 3 M 3 C 1 A 3 0 5 9 5 8 6 , N R F -2015R1A3A2066301).Scopu

Steered Pull Simulation to Determine Nanomechanical Properties of Cellulose Nanofiber

Cellulose nanofiber (CNF) exhibits excellent mechanical properties, which has been extensively proven through experimental techniques. However, understanding the mechanisms and the inherent structural behavior of cellulose is important in its vastly growing research areas of applications. This study focuses on taking a look into what happens to the atomic molecular interactions of CNF, mainly hydrogen bond, in the presence of external force. This paper investigates the hydrogen bond disparity within CNF structure. To achieve this, molecular dynamics simulations of cellulose I β nanofibers are carried out in equilibrated conditions in water using GROMACS software in conjunction with OPLS-AA force field. It is noted that the hydrogen bonds within the CNF are disrupted when a pulling force is applied. The simulated Young’s modulus of CNF is found to be 161 GPa. A simulated shear within the cellulose chains presents a trend with more hydrogen bond disruptions at higher forces

Chitosan Nanofiber and Cellulose Nanofiber Blended Composite Applicable for Active Food Packaging

This paper reports that, by simply blending two heterogeneous polysaccharide nanofibers, namely chitosan nanofiber (ChNF) and cellulose nanofiber (CNF), a ChNF–CNF composite was prepared, which exhibited improved mechanical properties and antioxidant activity. ChNF was isolated using the aqueous counter collision (ACC) method, while CNF was isolated using the combination of TEMPO oxidation and the ACC method, which resulted in smaller size of CNF than that of ChNF. The prepared composite was characterized in terms of morphologies, FT-IR, UV visible, thermal stability, mechanical properties, hygroscopic behaviors, and antioxidant activity. The composite was flexible enough to be bent without cracking. Better UV-light protection was shown at higher content of ChNF in the composite. The high ChNF content showed the highest antioxidant activity in the composite. It is the first time that a simple combination of ChNF–CNF composites fabrication showed good mechanical properties and antioxidant activities. In this study, the reinforcement effect of the composite was addressed. The ChNF–CNF composite is promising for active food packaging application