The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform

Gilchrist M. D. - One of the best experts on this subject based on the ideXlab platform.

  • The use of variotherm systems for Microinjection Molding
    'Wiley', 2016
    Co-Authors: Su Quanliang, Zhang Nan, Gilchrist M. D.
    Abstract:

    Microinjection Molding (μIM) is a fast-developing technology which is used to produce polymeric microcomponents or components with micro/nanoscale features, such as are used in many fields including microfluidic diagnostics, microneedle drug delivery devices, microgears, and microswitches. The capabilities and performance of the Microinjection Molding Process can be improved by incorporating a variotherm system. This leads to improved component quality, especially for high aspect ratio features. It can also help to increase the polymer flow path, improve feature replication, reduce residual stresses and molecular orientations, and also can eliminate weld lines. This article reviews the use of different variotherm systems in μIM, and describes how simulation of its use can provide insight when designing a mold cavity or a component with challenging microfeatures. The article highlights important problems, challenges and areas for further research. An increased understanding of these issues will provide opportunities to enhance further developments in the μIM Process.Enterprise IrelandUniversity College DublinChinese Scholarship Counci

  • Manufacturing microstructured tool inserts for the production of polymeric microfluidic devices
    'IOP Publishing', 2016
    Co-Authors: Zhang Nan, Srivastava, Amit P., Kirwan Brendan, Byrne Richard, Fang Fengzhou, Browne, David J., Gilchrist M. D.
    Abstract:

    Tooling is critical in defining multi-scale patterns for mass production of polymeric microfluidic devices using the Microinjection Molding Process. In the present work, fabrication of various microstructured tool inserts using stainless steel, nickel and bulk metallic glasses (BMGs) is discussed based on die-sinking EDM (electrical discharge machining), electroforming, focused ion beam milling and thermoplastic forming Processes. Tool performance is evaluated in terms of surface roughness, hardness and tool life. Compared to stainless steel, nickel and BMGs are capable of integrating length scales from 100 to 10−8 m and are good candidates for producing polymeric microfluidics. Selection of tool materials and manufacturing technologies should consider the end-user requirements of actual applications.Enterprise IrelandEuropean Commission - European Regional Development Fun

  • Characterization of Microinjection Molding Process for milligram polymer microparts
    'Wiley', 2014
    Co-Authors: Zhang Nan, Gilchrist M. D.
    Abstract:

    Injection Molding small milligram components requires precise metering and high-speed injection. Industrially, metering can be maintained either by using small injection screws (≤14 mm in diameter) or plungers as small as 3 mm diameter and/or by having very large sprues and runners. Although large sprues and runners increase metering volume, they hide the effect of Process parameters on microcomponents. Consequently, knowledge of conventional injection Molding is not transferable to Microinjection Molding, making quality control and optimization difficult. We investigated the filling and postfilling behavior of 25 mm3 microdumbbell specimens with 289 mm3 sprue and runner by in-line Process monitoring. Design of Experiments were carried out to characterize the effects of Process parameters on cavity filling and postfilling behavior. Process characterization indicated that the machine transition from velocity control to pressure control (V-P transition) was around 10 ms: this was comparable to cavity filling time and had a significant effect on cavity filling behavior. Traditional short shot trials cannot provide the correct shot size for small parts, but introduce the effect of holding pressure into cavity filling. Based on a shot size optimization method using only cavity pressure and screw velocity, we eliminated the effect of holding parameters on cavity filling.Deposited by bulk impor

  • Flow Induced Crystallization of Poly(ether-block-amide) from the Microinjection Molding Process and its Effect on Mechanical Properties
    'Wiley', 2014
    Co-Authors: Zhang Nan, Choi, Seong Ying, Gilchrist M. D.
    Abstract:

    Crystallization during Microinjection Molding is investigated relative to Process conditions. Modulus and hardness of the skin layer are higher than the core layer, regardless of core structure. Young's modulus, strain at break and yield stress all increase with an increase of skin ratio. The relationship between Process, morphology and mechanical properties is studied for micro products. By using in-line Process monitoring, flow induced crystallization is characterized by shear stress and apparent specific work. Shear stress is shown to be a good candidate to characterize the formation of highly oriented structures under actual Microinjection Molding Processes. This may provide a method for in-line control of morphology development, and then final properties, by controlling the flow conditions.Deposited by bulk importNeeds citation details. JG 2014-09-2

Andreas Tunnermann - One of the best experts on this subject based on the ideXlab platform.

  • development of a low cost high precision three layer 3d artificial compound eye
    Optics Express, 2013
    Co-Authors: Hao Zhang, David L Mccray, Sebastian Scheiding, Neil J Naples, Andreas Gebhardt, Stefan Risse, Ramona Eberhardt, Andreas Tunnermann
    Abstract:

    Artificial compound eyes are typically designed on planar substrates due to the limits of current imaging devices and available manufacturing Processes. In this study, a high precision, low cost, three-layer 3D artificial compound eye consisting of a 3D microlens array, a freeform lens array, and a field lens array was constructed to mimic an apposition compound eye on a curved substrate. The freeform microlens array was manufactured on a curved substrate to alter incident light beams and steer their respective images onto a flat image plane. The optical design was performed using ZEMAX. The optical simulation shows that the artificial compound eye can form multiple images with aberrations below 11 μm; adequate for many imaging applications. Both the freeform lens array and the field lens array were manufactured using Microinjection Molding Process to reduce cost. Aluminum mold inserts were diamond machined by the slow tool servo method. The performance of the compound eye was tested using a home-built optical setup. The images captured demonstrate that the proposed structures can successfully steer images from a curved surface onto a planar photoreceptor. Experimental results show that the compound eye in this research has a field of view of 87°. In addition, images formed by multiple channels were found to be evenly distributed on the flat photoreceptor. Additionally, overlapping views of the adjacent channels allow higher resolution images to be re-constructed from multiple 3D images taken simultaneously.

Giovanni Lucchetta - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the influence of part thickness on the replication of micro structured surfaces by injection Molding
    Materials & Design, 2016
    Co-Authors: Davide Masato, Marco Sorgato, Giovanni Lucchetta
    Abstract:

    Abstract The achievement of an adequate accuracy of the Microinjection Molding Process applied to the replication of micro-features is a complex task. The selection of Process parameters and the geometry of the molded part influences the filling flow of the melt inside the mold cavity as well as the final quality of the replicated micro-features. In this work, the replication of a micro-structured surface is studied in relation to the thickness of the molded part. In particular, the effects of a rapid heat cycle Molding Process, cavity air evacuation, part thickness are experimentally evaluated. The analysis of the experimental data showed that the thickness of the main flow region and the Molding temperature are significant factor affecting the replication quality. In particular, a combination of small cavity thickness and a high mold temperature (above T g ) can be effective in increasing the replicated height of micro-features. Experimental results also point out the correlation between the holding pressure and the distance from the injection location. An effective approach to the design of both the part and the Process, should consider that the selection of Process parameters must be related to design of the mold cavity.

Hao Zhang - One of the best experts on this subject based on the ideXlab platform.

  • development of a low cost high precision three layer 3d artificial compound eye
    Optics Express, 2013
    Co-Authors: Hao Zhang, David L Mccray, Sebastian Scheiding, Neil J Naples, Andreas Gebhardt, Stefan Risse, Ramona Eberhardt, Andreas Tunnermann
    Abstract:

    Artificial compound eyes are typically designed on planar substrates due to the limits of current imaging devices and available manufacturing Processes. In this study, a high precision, low cost, three-layer 3D artificial compound eye consisting of a 3D microlens array, a freeform lens array, and a field lens array was constructed to mimic an apposition compound eye on a curved substrate. The freeform microlens array was manufactured on a curved substrate to alter incident light beams and steer their respective images onto a flat image plane. The optical design was performed using ZEMAX. The optical simulation shows that the artificial compound eye can form multiple images with aberrations below 11 μm; adequate for many imaging applications. Both the freeform lens array and the field lens array were manufactured using Microinjection Molding Process to reduce cost. Aluminum mold inserts were diamond machined by the slow tool servo method. The performance of the compound eye was tested using a home-built optical setup. The images captured demonstrate that the proposed structures can successfully steer images from a curved surface onto a planar photoreceptor. Experimental results show that the compound eye in this research has a field of view of 87°. In addition, images formed by multiple channels were found to be evenly distributed on the flat photoreceptor. Additionally, overlapping views of the adjacent channels allow higher resolution images to be re-constructed from multiple 3D images taken simultaneously.

Danyang Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Multi-Objective Optimizations for Microinjection Molding Process Parameters of Biodegradable Polymer Stent
    'MDPI AG', 2018
    Co-Authors: Kui Liu, Minjie Wang, Danyang Zhao, Jianhua Hou
    Abstract:

    Microinjection Molding technology for degradable polymer stents has good development potential. However, there is a very complicated relationship between Molding quality and Process parameters of Microinjection, and it is hard to determine the best combination of Process parameters to optimize the Molding quality of polymer stent. In this study, an adaptive optimization method based on the kriging surrogate model is proposed to reduce the residual stress and warpage of stent during its injection Molding. Integrating design of experiment (DOE) methods with the kriging surrogate model can approximate the functional relationship between design goals and design variables, replacing the expensive reanalysis of the stent residual stress and warpage during the optimization Process. In this proposed optimization algorithm, expected improvement (EI) is used to balance local and global search. The finite element method (FEM) is used to simulate the micro-injection Molding Process of polymer stent. As an example, a typical polymer vascular stent ART18Z was studied, where four key Process parameters are selected to be the design variables. Numerical results demonstrate that the proposed adaptive optimization method can effectively decrease the residual stress and warpage during the stent injection Molding Process

  • Multi-Objective Optimizations of Biodegradable Polymer Stent Structure and Stent Microinjection Molding Process
    MDPI AG, 2017
    Co-Authors: Xinyu Wang, Yunbo Wei, Tao Liu, Minjie Wang, Danyang Zhao, Aike Qiao, Yahua Liu
    Abstract:

    Biodegradable stents made of poly-l-lactic acid (PLLA) have a promising prospect thanks to high biocompatibility and a favorable biodegradation period. However, due to the low stiffness of PLLA, polymeric stents have a lower radial stiffness and larger foreshortening. Furthermore, a stent is a tiny meshed tube, hence, it is difficult to make a polymeric stent. In the present study, a finite element analysis-based optimization method combined with Kriging surrogate modeling is firstly proposed to optimize the stent structure and stent Microinjection Molding Process, so as to improve the stent mechanical properties and Microinjection Molding quality, respectively. The Kriging surrogate models are constructed to formulate the approximate mathematical relationships between the design variables and design objectives. Expected improvement is employed to balance local and global search to find the global optimal design. As an example, the polymeric ART18Z stent was investigated. The mechanical properties of stent expansion in a stenotic artery and the Molding quality were improved after optimization. Numerical results demonstrate the proposed optimization method can be used for the computationally measurable optimality of stent structure design and stent Microinjection Molding Process