Sintesis Nanofiber PVP dengan Ekstrak Basella rubra Linn. Menggunakan Metode Elektrospinning

Pembalut luka alternatif dari lembaran serat nano telah dikembangkan baru-baru ini. Aktivitas antioksidan dan antibakteri berperan penting dalam proses penyembuhan luka. Penelitian ini bertujuan untuk menggabungkan sifat ekstrak Bassela rubra Linn. (EBRL) menjadi serat nano polivynil pyrrolidone (PVP) dengan metode elektrospinning. Langkah pertama yang dilakukan adalah menimbang Bassela rubra L. sebanyak 8 gram dan membungkus kedalam kertas saring. Kemudian diekstraksi dengan menggunakan etanol 99% sebagai pelarut pada suhu ± 78 oC. Langkah selanjutnya adalah membuat nanofiber dengan metode elektrospinning dengan menimbang PVP (Polivinil pirrolidon) sebanyak 8%wt. Menambahkan ekstrak Bassela rubra L. sebanyak 2%wt, 5%wt dan 8%wt pada larutan kedalam jarum suntik. Lalu mengatur laju alir 1 mL/jam, jarak antara spineret dengan kolektor 10 cm, dan tegangan 12kV. Dalam pengaplikasian nanofiber dengan EBRL diperlukan ukuran serat tertentu, maka dalam penelitian ini dilakukan pengamatan dampak komposisi EBRL terhadap diameter dan distribusinya. Metode ini dimulai dengan menginjeksikan larutan PVP dan EBRL dengan berbagai komposisi menuju kolektor dalam seperangkat alat elektrospinning. Morfologi nanopartikel telah dianalisa menggunakan metode Scanning Electron Microscopy (SEM). Perbedaan komposisi EBRL memberikan diameter dan distribusi diameter yang berbeda-beda. Hal ini dapat dipengaruhi oleh bentuk Taylor Cone dari larutan yang diinjeksikan.An alternative wound dressing based on nanofiber mats have been developed recently. The antioxidant and antibacterial activity play an important role in wound healing process. This study aims to combine the properties of Bassela rubra Linn. (EBRL) extract into polivynil pyrrolidone (PVP) nanofibers using the electrospinning method. The first step is to weigh 8 grams of basella rubra linn and wrap it in filter paper. Then extracted using 99% ethanol as a solvent at a temperature of ± 78 oC. The next step is to make nanofibers using the electrospinning method by weighing 8% wt of PVP (Polyvinyl pyrrolidone). Basella rubra linn extract as much as 2% wt, 5% wt and 8% wt in the solution into a syringe. Then assistance with the flow rate of 1 mL / hour, the distance between the spineret and the collector is 10 cm, coating the collector with aluminum foil, and providing 12kV voltage assistance. In the application of nanofibers with EBRL, a certain fiber size is required, so in this study, we observed the impact of EBRL on its diameter and distribution. This method begins by injecting PVP and EBRL solutions of various compositions into the collector in a set of electrospinning devices. The morphology of the nanoparticles was analyzed using the Scanning Electron Microscopy (SEM) method. Differences in the composition of EBRL provide different diameter and diameter distribution. This can be constructed by the Taylor Cone form of the solution that is injected.

Numerical Analysis on the Stability Conditions of an Electrohydrodynamic Jet

The Taylor cone jet is a well-known electrohydrodynamic flow (EHD), usually produced by applying an external electric field to a capillary liquid. The generation of this kind of flow involves a multi-phase and a multi-physics process and its stability has a specific operation window. This operating window is intrinsically dependent on the flow rate and magnitude of the applied electric voltage. In case high voltages are applied to the jet it can atomize and produce an electrospray. Our work presents a numerical study of the process of atomization of a Taylor cone jet using computational fluid dynamics (CFD). The study intents to assess the limit conditions of operation and the applied voltage needed to stabilize an electrospray. The numerical model was implemented within OpenFOAM, where the multi-phase hydrodynamics equations are solved using a volume-of-fluid (VOF) approach. This method is coupled with the Maxwell equations governing an electrostatic field, in order to incorporate the electric body forces into the incompressible Navier-Stokes equations. The leaky-dielectric model is used and, therefore, the interface between the two phases is subject to the hydrodynamic surface tension and electric stress (Maxwell stress). This allows a leakage of charge though the phase due to ohmic conduction. Thus, the permittivity and conductivity of the phases are taken into consideration. A two-fluid system with relevant electric properties can be categorized as, dielectric-dielectric, dielectric-conducting, and conducting-conducting considering the electrical conductivity and permittivities of the participating phases. Due to the usage of the leaky-dielectric model, it is possible to simulate any of this physical situations. By increasing the applied voltage reaches a value where the cone instability is verified, allowing a discussion on this effect. It is demonstrated that to adequately model the process of atomization a fine grid refinement is needed. The validation of the numerical model is made by comparing against diverse experimental data, for the case of a stable jet. The diameter and velocity of the droplet and the electric current of the jet are the main variables that are compared with previous results. The tests were performed with Heptane. The cone and the jet are strongly affected by the flow rate. The dimensionless diameter, as a function of the dimensionless flow rate, agrees with the scaling laws. The model predicts accurate results over a wide range of flow rates with an accuracy of around 10%. The results are obtained using structured meshes.

Sketch-Based Tensor Decomposition for Non-Parametric Monitoring of Electrospinning Processes

Electrospinning is a promising process to fabricate functional parts from macrofibers and nanofibers of bio-compatible materials including collagen, polylactide (PLA), and polyacrylonitrile (PAN). However, the functionality of the produced parts highly rely on quality, repeatability, and uniformity of the electrospun fibers. Due to the variations in material composition, process settings, and ambient conditions, the process suffers from large variations. In particular, the fiber formation in the stable regime (i.e., Taylor cone and jet) and its propagation to the substrate plays the most significant role in the process stability. This work aims to designing a fast process monitoring tool from scratch for monitoring the dynamic electrospinning process based on the Taylor cone and jet videos. Nevertheless, this is challenging since the videos are of high frequency and high dimension, and the monitoring statistics may not have a parametric distribution. To achieve this goal, a framework integrating image analysis, sketch-based tensor decomposition, and non-parametric monitoring, is proposed. In particular, we use Tucker tensor-sketch (Tucker-TS) based tensor decomposition to extract the sparse structure representations of the videos. Additionally, the extracted monitoring variables are non-normally distributed, hence non-parametric bootstrap Hotelling T2 control chart is deployed to handle this issue during the monitoring. The framework is demonstrated by electrospinning a PAN-based polymeric solution. Finally, it is demonstrated that the proposed framework, which uses Tucker-TS, largely outperformed the computational speed of the alternating least squares (ALS) approach for the Tucker tensor decomposition, i.e., Tucker-ALS, in various anomaly detection tasks while keeping the comparable anomaly detection accuracy.

Secondary Breakup Characteristics and Mechanism of Single Electrified Al/N-Decane Nanofluid Fuel Droplet in Electrostatic Field

The combustion characteristics of nanofluid fuels have been widely investigated, but rare studies on the atomization were reported. Atomization is an imperative and crucial step to improve the combustion performance of nanofluid fuels, and the secondary breakup of droplets is an important segment for atomization to produce uniform fine droplets and distribute nanoparticles in each droplet. This paper firstly presents the secondary breakup characteristics of single electrified Al/n-decane nanofluid fuel droplets and revealed the mechanism of the secondary breakup. The results demonstrated that fine droplets could be produced in the electrostatic field and Al nanoparticles were distributed in each droplet. Before the breakup, the single electrified droplets experienced surface charge transportation, deformation, and Taylor cone formation. A gradient of the electric field deformed the droplet to produce the Taylor cone. As the Taylor cones were stabilized, the fluid was extruded from the tips of stable Taylor cones to produce jet filament parallel to the electric field direction and correspondingly broke up into fine sub droplets. At the nanoparticle concentration range of 1.0~10 mg/mL, the minimum average diameter of breakup sub droplets could achieve ~55.4 μm at 6.0 mg/mL. The Al nanoparticle concentration had a significant effect on the breakup performance by influencing the physical properties and charging. The order of the Charge-to-Mass ratio magnitude was 10−7~10−5 C/kg. Furthermore, the secondary breakup mechanism of single electrified nanofluid fuel droplets in the uniform electrostatic field was revealed by analyzing the droplet surface charge, deformation, Taylor cone formation, and nanoparticle concentration effect.