Abdullahil Kafy

Transparent and Flexible Cellulose Nanocrystal/Reduced Graphene Oxide Film for Proximity Sensing

The rapid development of touch screens as well as photoelectric sensors has stimulated the fabrication of reliable, convenient, and human-friendly devices. Other than sensors that detect physical touch or are based on pressure sensing, proximity sensors offer controlled sensibility without physical contact. In this work we present a transparent and eco-friendly sensor made through layer-by-layer spraying of modified graphene oxide filled cellulose nanocrystals on lithographic patterns of interdigitated electrodes on polymer substrates, which help to realize the precise location of approaching objects. Stable and reproducible signals generated by keeping the finger in close proximity to the sensor can be controlled by humidity, temperature, and the distance and number of sprayed layers. The chemical modification and reduction of the graphene oxide/cellulose crystal composite and its excellent nanostructure enable the development of proximity sensors with faster response and higher sensitivity, the integration of which resolves nearly all of the technological issues imposed on optoelectronic sensing devices.

Cellulose long fibers fabricated from cellulose nanofibers and its strong and tough characteristics

Cellulose nanofiber (CNF) with high crystallinity has great mechanical stiffness and strength. However, its length is too short to be used for fibers of environmentally friendly structural composites. This paper presents a fabrication process of cellulose long fiber from CNF suspension by spinning, stretching and drying. Isolation of CNF from the hardwood pulp is done by using (2, 2, 6, 6-tetramethylpiperidine-1-yl) oxidanyl (TEMPO) oxidation. The effect of spinning speed and stretching ratio on mechanical properties of the fabricated fibers are investigated. The modulus of the fabricated fibers increases with the spinning speed as well as the stretching ratio because of the orientation of CNFs. The fabricated long fiber exhibits the maximum tensile modulus of 23.9 GPa with the maximum tensile strength of 383.3 MPa. Moreover, the fabricated long fiber exhibits high strain at break, which indicates high toughness. The results indicate that strong and tough cellulose long fiber can be produced by using ionic crosslinking, controlling spinning speed, stretching and drying.

Calcinated tea and cellulose composite films and its dielectric and lead adsorption properties.

In this paper, calcinated tea and cellulose composite (CTCC) films were fabricated via solution casting method. Chemical structure, morphology, crystallinity and thermal stability of the fabricated films were characterized by using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. The effect of calcinated tea loading on the properties of the prepared CTCC films was studied. The results suggest that the prepared CTCC films show higher mechanical properties, thermal stability and dielectric constant than the neat cellulose film. In addition, the CTCC films adsorb Pb2+ ions and its adsorption performance depends on the calcinated tea content and pH level. The CTCC films are useful for sensors, flexible capacitor as well as lead adsorption applications.

Preparation and characterisation of cellulose ZnO hybrid film by blending method and its glucose biosensor application

Abstract This paper reports an inexpensive, flexible and disposable cellulose ZnO hybrid film (CZHF) and its feasibility for a conductometric glucose biosensor. CZHF is fabricated by simply blending ZnO nanoparticles with cellulose solution prepared by dissolving cotton pulp with lithium chloride/N, N-dimethylacetamide solvent. After curing in isopropyl alcohol and water mixture, the CZHF is obtained. The enzyme glucose oxidase is immobilised into the CZHF by physical adsorption method. The enzyme activity of the glucose biosensor increases as the ZnO weight ratio increases linearly. The CZHF can detect glucose in the range of 1–12 mM.

Green all-cellulose nanocomposites made with cellulose nanofibers reinforced in dissolved cellulose matrix without heat treatment

Green all-cellulose nanocomposites were fabricated by adding reinforcing cellulose nanofiber (CNF) to a matrix of dissolved cellulose. CNFs were isolated from one dried native hardwood bleached Kraft pulp and office waste recycled deinked copy/printing paper (DIP) by using the TEMPO oxidation method. The cellulose was dissolved by using DIP and DMAc/LiCl solvent without heat treatment and solvent exchange to form a matrix of the all-cellulose nanocomposites. The DIP was not only selected for CNF isolation, but also for the cellulose matrix. The isolated CNFs and the all-cellulose nanocomposites were characterized by atomic force microscopy, thermogravimetry–differential thermal analysis, X-ray diffraction and mechanical tensile testing. The green all-cellulose nanocomposites made without heat treatment offered better thermal stability, crystallinity and mechanical properties than the heat treated ones. CNFs isolated from two resources show similar reinforcement capacity in all-cellulose nanocomposites. All-cellulose nanocomposite fabrication by dissolving cellulose without heat treatment and solvent exchange is a simple way that saves energy and chemicals.

Ultrasonic wave propagation of flexible piezoelectric polymer for tactile actuator: simulation and experiment

This study deals with ultrasonic wave propagation on a piezoelectric polymer substrate for tactile actuator. On the piezoelectric polymer substrate, a pair of interdigital transductor (IDT) electrodes is patterned by lift-off process and a resonator is made by exciting the IDTs. A standing wave is generated between the pair of IDT electrodes, of which the wavelength matches with the distance between two IDTs. The standing ultrasonic waves can give different textures to the users. The wave propagation in this periodic structure on the polymer substrate is studied by harmonic and transient analysis. Vertical displacement and induced voltage at the output IDT electrode are calculated and the ultrasonic wave generation is experimentally verified. The proposed concept of tactile actuator based on ultrasonic wave is explained.

Array haptic actuator for flight simulator

Array haptic actuator to realize texture of button for virtue flight simulator is fabricated by using cellulose acetate (CA) film. The haptic actuator has independent 3 × 3 cells for identical vibration. Each cell consists of topside CA layer and bottomside CA layer with two pillars. Two ends of topside CA layer are fixed on the pillars similar with fixed end beam. By an electrostatic force in the presence of electric field, the topside CA layer vibrates. Each cell shows its resonance frequency peak in the capable frequency range of vibrotactile feeling from 100 Hz to 500 Hz. The acceleration performance is shown to be higher than vibrotactile threshold on wide frequency band from 100 Hz to 400 Hz.

Multi Functional and Smart Graphene Filled Polymers as Piezoelectrics and Actuators

Graphite and its derivative materials are widely used in fabricating energy harvesters and are known as materials of this generation. The excellent applications of these materials in technology come from their superior electronic properties. Piezoelectric , Actuator and other tactile materials based on graphene have come up with substantially improved properties. The present chapter deals with these aspects of graphene filled polymer nanocomposites where a thorough investigation of the design and properties of them is carried out. Effect of homogeneous distribution of graphene within the matrix, interfacial interaction and functionalization of fillers are discussed to bring dynamic control to nanoscale actuators and piezoelectrics. In addition to explaining the fundamental requirements to make the best piezoelectric and actuator materials, the existing confronts to guide future progress is also undertaken in this study.

Synthesis and characterization of graphene/cellulose nanocomposite

Cellulose is one of attractive natural polysaccharides in nature due to its good chemical stability, mechanical strength, biocompatibility, hydrophilic, and biodegradation properties [1-2]. The main disadvantages of biopolymer films like cellulose are their poor mechanical properties. Modification of polymers with inorganic materials is a new way to improve polymer properties such as mechanical strength [3-4]. Presently, the use of graphene/graphene oxide (GO) in materials research has attracted tremendous attention in the past 40 years in various fields including biomedicine, information technology and nanotechnology[5-7]. Graphene, a single sheet of graphite, has an ideal 2D structure with a monolayer of carbon atoms packed into a honeycomb crystal plane. Using both experimental and theoretical scientific research, researchers including Geim, Rao and Stankovich [8-10] have described the attractiveness of graphene in the materials research field. Due to its sp2 hybrid carbon network as well as extraordinary mechanical, electronic, and thermal properties, graphene has opened new pathways for developing a wide range of novel functional materials. Perfect graphene does not exist naturally, but bulk and solution processable functionalized graphene materials including graphene oxide (GO) can now be prepared [11-13].The large surface area of GO has a number of functional groups, such as -OH, -COOH, -O- , and C=O, which make GO hydrophilic and readily dispersible in water as well as some organic solvents[14] , thereby providing a convenient access to fabrication of graphene-based materials by solution casting. According to several reports [15-17], GO can be dispersed throughout a selected polymer matrix to make GO-based nanocomposites with excellent mechanical and thermal properties. Since GO is prepared from low-cost graphite, it has an outstanding price advantage over CNTs, which has encouraged studies of GO/synthetic polymer composites [18-20]. In some reported papers, graphene oxide has also been used to reinforce polysaccharide matrices such as carboxymethyl cellulose-starch[21]. Here, we report a simple and environmentally benign preparation of GO/cellulose nanocomposite films by a simple solution mixing-curing method.

Fabrication and characterization of cellulose nanofiber/graphene oxide blended fibers

Hybridization of organic and inorganic material opens many opportunities by taking the advantages of both materials. Cellulose is one of the most abundant material on earth which is biocompatible, cheap, lightweight, and environment friendly. Cellulose nanofibers (CNF) have high mechanical strength because of high crystallinity. Graphene Oxide (GO) is one forms of carbon which is produced from graphite flake. CNF and GO composites (CNFGO) can offer advantages in terms of mechanical strength as well as electrical properties. CNF is extracted from hardwood pulp using mild TEMPO treatment and aqueous counter collision (ACC). GO is synthesized from graphite flakes following improved synthesize of graphene oxide. CNFGO suspension is prepared using a simple blending method. CNFGO fiber is fabricated by spinning CNFGO suspension in CaCl2 coagulation solution. The composite fiber is characterized using Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD). Mechanical Properties of the composite fibers is also investigated.