A method of producing sharp tipped plastic hollow microneedle arrays using microinjection moulding is presented in this paper. Unlike traditional approaches, three mould inserts were used to create the sharp tips of the microneedles. Mould inserts with low surface roughness were fabricated using a picosecond laser machine. Sharp tipped plastic hollow microneedles 500 μm in height were fabricated using a microinjection moulding machine developed by the authors' group. In addition, the strength of the microneedle was studied by simulation and penetration experiments. Results show that the microneedles can penetrate into skin, delivering liquid successfully without any breakage or severe deformation. Techniques presented in this paper can be used to fabricate sharp tipped plastic hollow microneedle arrays massively with low cost.
Male, Ph.D. candidate in Tohoku university. His research interests mainly focus on the quantitative analysis for microstructure of die castings and compounds using mathematical morphology. V arious types of surface defects of die casting products may occur due to the complex situation inside the die. The evaluation and classification of surface defects on die castings have long been an important and challenging issue. Traditionally, visual inspection depending on technicians' individual experience has been used in factories to examine whether the surface defects are acceptable or not. However, this calls for high requirement on the technicians' skill. Even professional technicians will find it difficult to balance the conflict between efficiency and accuracy, since the work is so subjective, tedious and monotonous.Image processing technology provides a viable alternative to automatically detect the defects and evaluate the defect severity. Wong [1] et al. adopted fuzzy logic algorithm to surface images after image Abstract: It is necessary in factories to assess the severity of the surface defects of castings, as a slight surface defect will be taken as qualified when it brings no bad effect or it can be removed by the subsequent processing. In practical production, professional technicians visually inspect the surface defect severity according to their individual experience. Therefore, it is difficult for them to maintain the same standard and accuracy in the subjective, tedious and labor-intensive work. Recently, image processing techniques based on optical images have been applied to achieve better accuracy and high efficiency. Unfortunately, optical images cannot directly quantify surface depth, which works as a crucial factor in the practical assessment of surface defect severity. The surface roughness evaluation algorithm, which takes into account of both area and depth information of the assessed surface, was applied to directly characterize surface defect severity based on surface asperity rather than optical image. The results using standard casting pieces show that surface defect severity has no apparent dependence on surface roughness. However, the subsequent results show that the root-mean-squared-deviation (RMSD) of surface gradient of flow line defects positively correlates with the increase of defect severity. The other types of defect do not present such tendency. Thus, practical workpieces with flow line defects on the surface were used to verify the universality of this tendency. The results show that surface roughness of an unqualified workpiece is larger than that of a qualified workpiece after surface slope adjustment, but presents no obvious coincidence before the adjustment. In contrast, the RMSD of an unqualified workpiece, no matter before or after the adjustment, is larger than that of a qualified one.
In order to study the impact on the roller abrasion resistance of the surface structure parameters such as stripes depth and number, roller abrasion model experiments were carried out with quartz sand as granular material and optimal design method was used to arrange testing program. Based on structural features of roller press, a model test bed was build and stripes roller were design and manufactured according to similar principles. Roller surface structure parameters were determined by orthogonal polynomial regression design method. By processing the test data, a regression equation was obtained with stripes depth, number and the amount of wear as parameters. The results showed that: Stripes structure grinding rollers have better abrasion resistance than the light roller; The depth and the number of stripes have a greater impact on the abrasion resistance and there was an interaction between them; In the same conditions, when the stripe depth is fixed, the wear amount increases with the number of stripes increasing; when a fixed number of stripes, the wear amount decreases with stripes depth increasing.
A improved sliding friction coefficient model is presented based on road surface character and rubber character to analyze how the road character, tire and contact pressure affect the sliding friction coefficient. Improved the sliding friction coefficient model by introducing the theory of true contact with rough road and combined with the simplified rubber viscosity. Verifying the efficiency of the improved model through comparison with the dynamic friction coefficient of Savkoor. Analyzed the impact of contact pressure to the actual contact area and the contact pressure, and how tire and road surface character influence the sliding friction coefficient. The simulation result shows that the improved model can precisely analyze the impact of contact pressure,road surface character and tire to the sliding friction coefficient.
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