ABSTRACT
Based on an analysis of large sample data, this paper improves the calculation method of the fractal dimension in an electrospun membrane and proposes a method to generate a computer-aided design (CAD) model of an electrospun membrane under the control of fractal dimension. Fifteen electrospun membrane samples of PMMA and PMMA/poly(vinylidene fluoride) (PVDF) materials were prepared under similar concentrations and voltage parameters, and 525 SEM images of the surface morphology with a resolution of 2560 × 1920 were taken as a dataset. The feature parameters, such as fiber diameter and direction, are extracted from the image. Second, based on the minimum value of the power law behavior, the pore perimeter data were preprocessed to calculate the fractal dimensions. A 2D model was reconstructed randomly based on the inverse transformation of the characteristic parameters. The genetic optimization algorithm adjusts the fiber arrangement to realize the control of characteristic parameters, such as the fractal dimension. Based on the 2D model, a long fiber network layer with a thickness consistent with the depth of the SEM shooting is generated in ABAQUS software. Finally, a solid CAD model of the electrospun membrane with realistic thickness was constructed by combining multiple fiber layers. The result shows that the improved fractal dimension exhibits multifractal characteristics and distinct sample differences, which are more similar to the experimental results. The proposed 2D modeling method of the long fiber network can allow the control of various characteristic parameters, including the fractal dimension, and can generate the required model quickly.
ABSTRACT
Tool detachment during the machining process is often required by many image-based tool wear monitoring (TWM) systems. Tool detachment prevents the online mode of the wear measurement, extends the machining time, and contributes to measurement inaccuracy. Other alternatives of the image-based TWM systems have been developed with the image-acquisition device located statically near the tool position without the requirement for the tool detachment. However, due to its proximity to the machining site, the image-acquisition device may experience obstruction from the workpiece chips and the splash of coolant fluid during the machining process, resulting in non-optimal TWM. This article presents MicroEye - an online image-based TWM system with modular 3D-printed components to overcome the two problems. MicroEye offers great flexibility in its operation through the use of an active 6-DOF (degree of freedom) robotics arm with a camera at the end-effector. MicroEye does not require tool detachment to perform tool wear monitoring and can be safely placed outside the machining area. MicroEye is the first open-sourced, 3D-printed components and active dynamic-type TWM system for the application of micro-milling. MicroEye can be built at a low-cost (approximately US$ 872, including the camera). MicroEye is suitable for various micro-milling sites, from laboratory scale to middle-low workshop.
ABSTRACT
A number of studies on skin tissue regeneration and wound healing have been conducted. Electrospun nanofibers have numerous advantages for use in wound healing dressings. Here, we present an electrospinning method for alteration of the surface morphological properties of electrospun mats because most previous studies focused on the materials used or the introduction of bioactive healing agents. In this study, a micromachined human skin pattern mold was used as a collector in an electrospinning setup to replicate the pattern onto the surface of the electrospun mat. We demonstrated the successful fabrication of a nanofibrous mat with a human skin pattern. To verify its suitability for wound healing, a 14-day in vitro cell culture was carried out. The results indicated that the fabricated mat not only induces equivalent cell viability to the conventional electrospun mat, but also exhibits guidance of cells along the skin pattern without significant deterioration of pattern geometry.
