Centrifugal electrospinning (CES) was developed by integrating the electrospinning (ES) and centrifugal spinning (CS) concepts to produce oriented and diameter-controlled fibrous scaffolds which were then applied to stimulate the behaviour of fibroblast cells. During the fabrication process, polymer concentrations, rotational speeds, operating voltages, and needle sizes were key parameters to affect the diameters of produced fibres. The mathematical model indicated that the centrifugal force with the power of 2 was the main influence in fabricating thinner fibres, followed by electrostatic force with the power of 1. The developed CES technique could fabricate fibres scaffold ranging from 210 ± 50 nm to 2814 ± 96 nm by only applying low operating voltages and rotation speed which were 10 kV and up to 2000 rpm, respectively. Through optimum parameter, random and aligned nanofibrous were fabricated with the diameter being distributed mainly at 200–400 nm. Aligned nanofibrous demonstrated a high degree of orientation when 88% of the nanofibrous varied at 0°–10°. Compared to random structure, aligned nanofibrous presented high tensile strength, which was approximately 4.35 MPa and appropriate flexibility with 73% of elongation break. Aligned nanofibrous exhibited high cell viabilities with a 2.34 absorbance rate at day 14. The fibroblast cells elongated and accelerated in the orientation of the aligned nanofibrous. Results suggest that fibre aligned scaffolds are possible candidates for wound dressing application.

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This paper describes the fabrication of a structural scaffold consisting of both randomly oriented nanofibers and triangular prism patterns on the scaffold surface using a combination technique of electrospinning and collector templates. The polycaprolactone (PCL) nanofibers were electrospun over a triangular prism pattern mold, which acted as a template. The deposited scaffold was removed from the template to produce a standalone structural scaffold of three-dimensional micropatterned nanofibers. The fabricated structural scaffold was compared with flat randomly oriented nanofibers based on in vitro and in vivo studies. The in vitro study indicated that the structural scaffold demonstrated higher fibroblast cell proliferation, cell elongation with a 13.48 ± 2.73 aspect ratio and 70% fibroblast cell orientation compared with flat random nanofibers. Among the treatment groups, the structural scaffold escalated the wound closure to 92.17% on day 14. Histological staining of the healed wound area demonstrated that the structural scaffold exhibited advanced epithelization of the epidermal layer accompanied by mild inflammation. The proliferated fibroblast cells and collagen fibers in the structural scaffold appeared denser and arranged more horizontally. These results determined the potential of micropatterned scaffolds for stimulating cell behavior and their application for wound healing.

Activated sludge process is an important stage in Wastewater Treatment Plant (WWTP). In this study, model of the activated sludge process from Bunus Regional Sewage Treatment Plant Kuala Lumpur, Malaysia is developed. This paper focuses on modelling and model reduction of the WWTP system. The model with best fits of higher than 80% and the order of less than 10 is selected. For modelling purposes, data obtained is stimulated and modelled using System Identification technique which employ linear model ARX. For model reduction purposes, the high order model is reduced using model order reduction (MOR) of a combination of Singular Perturbation Approximation (SPA) and Frequency Domain Gramian based Model Reduction (FDIG) method. From the modelling results obtained, the ARX model with best fit of 85.11% is selected. Meanwhile, for the MOR FD-SPA technique, a 9th order model is selected with  reduction error between frequencies 0.05 rad/s and 1.4 rad/s.