A Comparative Study Between Weighing and Image Analysis Techniques for Predicting the Amount of Deposited Electrospun Nanofibres

Weighing and direct measurement are currently the two most common techniques used for estimating the amount of deposited nanofibres in electrospinning process. Nevertheless, due to its extremely small fibre size and mass, the task of measuring the weight or thickness of an electrospun nanofibres membrane is difficult and the results are arguable. This study evaluates the effectiveness of using greyscale image analysis for predicting the amount of deposited nanofibres compared to weighing technique. Polyvinyl alcohol electrospun nanofibres were collected at different deposition times on A4 black paper substrates. The substrates were weighed before and after deposition process and then scanned into 8 bit greyscale images. Analyses were carried out using ImageJ software, statistical analysis, high speed camera and scanning electron microscopy. At long deposition times, both techniques showed significant correlations between the measured values and deposition times. However, at short deposition times the weighing technique was found unreliable (p>0.05) compared to image analysis technique due to insignificant fibre masses compared to the weight variation of the substrates. Results suggest that image analysis technique was a better option to be used compared to weighing technique. This technique has the potential to be used as an automated online quality control in electrospun nanofibres manufacture

An investigation of using grey scale image analysis for predicting the amount of deposited electrospun nanofibres

When electrospinning, the amount of electrospun fibres deposited is difficult to determine due to the extremely small size and light weight of the fibres. Several methods have been used to predict the amount of deposited fibres including weighing, imaging and direct measurement. Although these methods work to a certain extent, they all have drawbacks that make them unsuitable for commercial scale process control. The methods are generally time consuming, destructive and only examine a small area of web. In this study, an image analysis method is used to predict the amount of electrospun fibres deposited over a significant area. When images of electrospun fibres are converted into grey scale images, it is suggested that the amount of fibres deposited can be predicted by measuring the grey scale intensity. A conventional weighing method was used to validate the image analysis results. The weighing method was found wanting when the deposition time was short (p>0.05). This was because the measured fibre masses were insignificant compared to the weight variation of the collector substrates. Statistical analyses showed that there were a strong correlation between grey scale intensity and deposition time especially at short deposition times. The results suggest that image analysis method could be used to predict the amount of deposited electrospun nanofibres. Further test on different polymers and different coloured substrates showed that the method was still capable to distinguish the samples. The developed method has the potential to be applied as an in-line non-destructive quality control method for electrospun fibre manufacture

The Effect of Deposition Time on Filtration Efficiency of Electrospun Nanofibre Water Filters

Growing concern over turbidity of river waters due to high presence of solid suspensions has encouraged the development of new type of efficient water filters. In this study, a new type of water filter was developed by incorporating electrospun nanofibres. The relationship between the amount of incorporated nanofibres in term of deposition time and filtration efficiency was studied. Nylon 6 solution at 20 wt.% concentration was electrospun onto standard glass fibre filters. A high voltage of 14 kV was supplied at the spinneret and electrospinning distance was set at 10 cm. Suspended solid retention test was conducted on the glass fibre filters using a vacuum filtration system based on BS EN 872 standard. The morphology of the filters was studied using scanning electron microscopy and ImageJ software. From the results, the suspended solid retention capability increased linearly with nanofibre deposition time. Due to small size of the nanofibres, the addition of nanofibre layer has increased the total porosity of the filter. Findings from this study could open up further understanding in new generation of water filters

Preparation, Characterization, and Electrical Conductivity Investigation of Multi-walled Carbon Nanotube-filled Composite Nanofibres

There is a growing interest in carbon nanofibre materials especially for applications that require high surface area, excellent chemical inertness, and good electrical conductivity. However, in certain applications a much higher electric conductivity is required before one can take the full advantage of the nanofibre network. Therefore, incorporating superconductive materials such carbon nanotubes is thought to be a feasible approach to enhance the electrical properties of the carbon nanofibres. The objectives of this study were to prepare and characterize multi-walled carbon nanotube-filled composite nanofibres. Carbon nanofibres were produced via electrospinning technique using precursor solutions of polyacrylonitrile in dimethylformamide loaded with different amount of multi-walled carbon nanotubes (MWCNT). The electrospun fibre samples were then pyrolyzed in a nitrogen-filled laboratory tube furnace. Characterization process was performed using scanning electron microscope (SEM), transmission electron microscope (TEM), and four-point probe method. It was found that the incorporation of MWCNT into the carbon nanofibre structures could significantly increase the electric properties of the nanofibres. The composite nanofibres with 0.1 wt.% of MWCNT loading has the highest electrical conductivity of 155.90 S/cm compared to just 10.71 S/cm of the pure carbon nanofibres. However, the electrical conductivity of the composite fibres reduced drastically when higher weight percentages of MWCNT were used. This was caused by agglomeration of MWCNT causing premature percolation, and broken fibre network as evidenced by SEM and TEM examinations. The results obtained from this study may facilitate improvements in the development of superconductive high surface area materials for electronic applications

Design and Development of Domestic Cyclone Dust Collector System Using TRIZ And CCD Method

In conventional vacuum cleaners, filter media or filter bags are used to physically separate dust and debris from flowing air streams. However, in such systems, the vacuum cleaner's efficiency diminishes over time as more debris is accumulated on the filter surface. In this study, a two-stage cyclone dust collector system was proposed, which can be attached to existing vacuum cleaners. The system was designed and developed using the integrated Theory of Inventive Problem Solving (TRIZ) and Classical Cyclone Design (CCD) method. The TRIZ method was implemented during the idea generation stage, where specific design solution strategies were reviewed. Theoretical analysis of the selected design was carried out using Classical Cyclone Design (CCD) method. Finally, a full-scale working prototype of the cyclone dust collector was fabricated for evaluation. Based on results, the cyclone dust collector system provides more than 99% fractional efficiency and 96% overall collection efficiency for particles with an average diameter of over 50 μm. The pressure drops and airflow inside the cyclone dust collector were also analysed. The results suggest that the proposed cyclone dust collector system would provide better filtration efficiency and less maintenance compared to the conventional system

Functional nanofibers in clothing for protection against chemical and biological hazards

Functional nanofibers have great potential to improve protection against chemical and biological warfare agents. This chapter reviews the history of chemical and biological warfare and existing protective technologies. The use of electrospinning to produce nanofibers for protective applications is also introduced. Previous studies demonstrate the applicability of electrospun nanofibers in protective fabric technologies. Advantages of these next generation protective materials include high penetration resistance, excellent breathability, low basis weight, low pressure drop, the potential for the incorporation of surface chemical functionality and simple processing equipment. Finally, the main development issues and potential research directions of electrospun nanofibers in protective applications are discussed

Three-Dimensional Uniaxially Aligned Nanofibre Construct Using Secondary Electrode Assisted Gap Electrospinning

Electrospinning is a simple, versatile, and scalable method of producing polymeric nanofibres from a solution or melt using electric charge. Due to their nanometre-scale diameters, electrospun fibres have been the subject of much study for applications that require a high surface area to volume ratio. However, challenges remain in spatially controlling the deposition of electrospun fibres due to the chaotic nature of electrospinning process. Due to the bending instability, electrospun fibres are typically deposited as random orientated fibres and furthermore, there is no control over the location where the fibres are deposited on the collector. Several techniques to control the deposition of electrospun fibres have been proposed; including the use of modified collectors and by reducing the tip-to-collector distances. Changes in solvent evaporation and the bending instability may reduce stretching of the fibre, resulting in larger diameter fibres. Recently, a new technique for controlling the deposition of electrospun fibres using charged secondary electrodes has been proposed and the results have been promising. In this study, a new approach of directly depositing uniaxially aligned nanofibres onto a holdable structure is demonstrated. The results suggest that the introduction of secondary electrodes charged with time-varying potentials could improve the alignment and distribution of fibres in gap electrospinning process. The new technique would be able to produce fibres for applications which have been previously limited by physical constraint of conventional electrospun fibres

Investigation on Fibre Diameter, Wettability and Tensile Behaviour of Electrospun Polyacrylonitrile Nanofibres

One of the major concerns in membrane distillation technology is membrane wettability. Surface functionalization using superhydrophobic electrospun nanofibre material is thought to be feasible and effective to overcome the issue. However, further understanding on characteristic and mechanical behaviour of electrospun fibres is required. This paper studied the effect of different electrospinning parameters on fibre diameter, wettability, and tensile behaviour of polyacrylonitrile electrospun nanofibres. Polyacrylonitrile in dimethyl-formamide solution of 10 wt.% concentration was electrospun under different applied voltages and electrospinning distances. The characteristic and behaviour of PAN electrospun nanofibres were characterised by using scanning electron microscope, water contact angle method and tensile test. Based on scanning electron micrographs, the average fibre diameters were in the range of nanometre. It was also observed that increasing the applied voltage would increase the fibre diameter, meanwhile, increasing the distance between spinneret and grounded collector would decrease fibre diameter and fibre deposition rate. The average contact angle and the tensile strength of PAN electrospun nanofibres also was determined in this study. The results from this study provide crucial information for the development of new filtration material for membrane distillation