Shreyas S. Limaye and Christina M. Mastrangelo
Healthcare-associated infections (HAIs) are a major cause of concern because of the high levels of associated morbidity, mortality, and cost. In addition, children and intensive…
Abstract
Healthcare-associated infections (HAIs) are a major cause of concern because of the high levels of associated morbidity, mortality, and cost. In addition, children and intensive care unit (ICU) patients are more vulnerable to these infections due to low levels of immunity. Various medical interventions and statistical process control techniques have been suggested to counter the spread of these infections and aid early detection of an infection outbreak. Methods such as hand hygiene help in the prevention of HAIs and are well-documented in the literature. This chapter demonstrates the utilization of a systems methodology to model and validate factors that contribute to the risk of HAIs in a pediatric ICU. It proposes an approach that has three unique aspects: it studies the problem of HAIs as a whole by focusing on several HAIs instead of a single type, it projects the effects of interventions onto the general patient population using the system-level model, and it studies both medical and behavioral interventions and compares their effectiveness. This methodology uses a systems modeling framework that includes simulation, risk analysis, and statistical techniques for studying interventions to reduce the transmission likelihood of HAIs.
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Wangyu Liu, Dong Sun, Aimin Tang and Mingke Li
Hydrogel is an excellent material for the fabrication of porous scaffold by mask-prototyping method. Different from the common commercial resin, hydrogel is hydrophilic and…
Abstract
Purpose
Hydrogel is an excellent material for the fabrication of porous scaffold by mask-prototyping method. Different from the common commercial resin, hydrogel is hydrophilic and hyperelastic, so that it cannot bear the conventional post-curing process to improve its mechanical properties. The purpose of this paper is to put forward a method to improve the curing bonding strength at the weak juncture of the porous hydrogel scaffold.
Design/methodology/approach
The working curve of the resin was obtained through the single layer cure experiment, and the energy accumulation model has been set up by MATLAB. Aimed at the specificity of material, a new method of partial curing on different kind of structure has been proposed. Under the same condition, only the tn2 needs to be changed to fabricate different test specimens with different accumulated energy between two layers. The tensile test is carried out with the authors’ preferred equipment.
Findings
The analysis reveals that accumulated energy can be changed by adjusting the key parameters, and the tensile test shows that when the accumulated energy is bigger, the ultimate tensile strength is higher.
Research limitations/implications
Subject to the equipment accuracy and specificity of material, some errors coming from the experiment and test might exist, but the authors believe they will not change their findings and conclusions in this paper.
Practical implications
The research provides a method which is different from the common methods but friendlier to improve the bonding strength of the hydrogel scaffold.
Social implications
This work can help to adjust the mechanical property of the scaffold used in tissue engineering.
Originality/value
This method can improve the bonding strength at weak juncture and give a direction for the design of porous scaffold.
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Mask projection micro‐stereolithography (MPμSLA) is an additive manufacturing process capable for fabricating true three‐dimensional microparts and hence, holds promise as a…
Abstract
Purpose
Mask projection micro‐stereolithography (MPμSLA) is an additive manufacturing process capable for fabricating true three‐dimensional microparts and hence, holds promise as a potential 3D MEMS fabrication process. With only a few MPμSLA systems developed and studied so far, the research in this field is inchoate and experimental in nature. In order to employ the MPμSLA technology for microfabrication, it is necessary to model its part building process and formulate a process planning method to cure dimensionally accurate microparts. The purpose of this paper is to formulate a process planning method for curing dimensionally accurate layers.
Design/methodology/approach
A MPμSLA system is designed and assembled. The process of curing a single layer in resin using this system is modeled as the layer cure model. The layer cure model is validated by curing test layers. This model is used to formulate a process planning method to cure dimensionally accurate layers. The process planning method is tested by conducting a case study.
Findings
The layer cure model is found to be valid within 3 percent for most of the features and within 10 percent for very small features (<250μm). The paper shows that ray tracing can be effectively used to model the process of irradiation of the resin surface in a MPμSLA system.
Research limitations/implications
The process planning method is applicable only to those imaging systems, which are aberration limited as opposed to diffraction limited. The dimensional errors in the lateral dimensions of single layers cured by MPμSLA have been modeled, but not the vertical errors in 3D parts.
Originality/value
In this paper, a process planning method for MPμSLA has been presented for the first time.
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Lifang Wu, Lidong Zhao, Meng Jian, Yuxin Mao, Miao Yu and Xiaohua Guo
In some three-dimensional (3D) printing application scenarios, e.g., model manufacture, it is necessary to print large-sized objects. However, it is impossible to implement…
Abstract
Purpose
In some three-dimensional (3D) printing application scenarios, e.g., model manufacture, it is necessary to print large-sized objects. However, it is impossible to implement large-size 3D printing using a single projector in digital light processing (DLP)-based mask projection 3D printing because of the limitations of the digital micromirror device chips.
Design/methodology/approach
A multi-projector DLP with energy homogenization (EHMP-DLP) scheme is proposed for large-size 3D printing. First, a large-area printing plane is established by tiling multiple projectors. Second, the projector set’s tiling pattern is obtained automatically, and the maximum printable plane is determined. Third, the energy is homogenized across the entire printable plane by adjusting gray levels of the images input into the projectors. Finally, slices are automatically segmented based on the tiling pattern of the projector set, and the gray levels of these slices are reassigned based on the images of the corresponding projectors.
Findings
Large-area high-intensity projection for mask projection 3D printing can be performed by tiling multiple DLP projectors. The tiled projector output energies can be homogenized by adjusting the images of the projectors. Uniform ultraviolet energy is important for high-quality printing.
Practical implications
A prototype device is constructed using two projectors. The printable area becomes 140 × 210 mm from the original 140 × 110 mm.
Originality/value
The proposed EHMP-DLP scheme enables 3D printing of large-size objects with linearly increasing printing times and high printing precision. A device was established using two projectors to practice the scheme and can easily be extended to larger sizes by using more projectors.
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Shih-Hsuan Chiu, Kun-Ting Chen, Sigit Tri Wicaksono, Jia-Rung Tsai and Sheng-Hong Pong
The aim of this study is to optimize the process parameters of area-forming rapid prototyping system to improve the model dimensional repeatability and to minimize the process…
Abstract
Purpose
The aim of this study is to optimize the process parameters of area-forming rapid prototyping system to improve the model dimensional repeatability and to minimize the process time as well.
Design/methodology/approach
Model dimensional repeatability is based on the dimensional standard deviation of the test sample. The significant factors that affect the model dimensional repeatability and process time are established by the fractional factorial design. Response surface methodology, based on the central composite design, is applied to evaluate the regression models of the response variables including prototype’s dimensional repeatability and processing time. Finally, a desirability function for each individual response variables is constructed to obtain the optimal process parameters.
Findings
The significant factors that have an impact on the main effects of response variables model dimensional repeatability and process time found by the fractional factorial design are curing time, light flux and platform moving velocity.
Originality/value
All previous studies were concerned with product accuracy in area-forming rapid prototyping system. In this work, we focus on optimization of model dimensional repeatability.
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Shih-Hsuan Chiu, Cheng-Lung Wu, Shun-Ying Gan, Kun-Ting Chen, Yi-Ming Wang, Sheng-Hong Pong and Hitoshi Takagi
The purpose of this study is to increase the thermal and mechanical properties of the photopolymer by filling with the copper powder for the application of rapid tooling.
Abstract
Purpose
The purpose of this study is to increase the thermal and mechanical properties of the photopolymer by filling with the copper powder for the application of rapid tooling.
Design/methodology/approach
In this study, the photopolymer is filled with the different loading of copper powder for investigating the thermal and mechanical properties of the copper/photopolymer composite. The thermal properties of the copper/photopolymer composite are characterized with the degradation temperature and with the thermal conductivity. The mechanical properties of copper/photopolymer composite are performed with the tensile strength and hardness testing. Moreover, the copper/photopolymer composite is imaged by using a scanning electron microscopic with energy dispersive spectroscopy.
Findings
The tensile strength of the copper/photopolymer composite is increased over 45 per cent at 20 phr copper loading. The hardness of the photopolymer has a negative correlation with the increasing copper loading and is decreased about 28.5 per cent at 100 phr copper loading. The degradation temperature of the copper/photopolymer composite is increased about 7.2 per cent at 70 phr copper loading. The thermal conductivity of the copper/photopolymer composite is increased over 65 per cent at 100 phr copper loading.
Originality/value
The photopolymer used in rapid prototyping system is generally fragile and has poor thermal properties. This study improves the thermal and mechanical properties of the photopolymer with the copper filling which has been never investigated in the field of rapid prototyping applications.
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Jae‐Won Choi, Ryan B. Wicker, Seok‐Hyun Cho, Chang‐Sik Ha and Seok‐Hee Lee
The paper's aim is to explore a method using light absorption for improving manufacturing of complex, three‐dimensional (3D) micro‐parts with a previously developed dynamic mask…
Abstract
Purpose
The paper's aim is to explore a method using light absorption for improving manufacturing of complex, three‐dimensional (3D) micro‐parts with a previously developed dynamic mask projection microstereolithography (MSL) system. A common issue with stereolithography systems and especially important in MSL is uncontrolled penetration of the ultraviolet light source into the photocrosslinkable resin when fabricating down‐facing surfaces. To accurately fabricate complex 3D parts with down‐facing surfaces, a chemical light absorber, Tinuvin 327™ was mixed in different concentrations into an acrylate‐based photocurable resin, and the solutions were tested for cure depths and successful micro‐part fabrication.
Design/methodology/approach
Tinuvin 327 was selected as the light absorber based on its high absorption characteristics (∼0.4) at 365 nm (the filtered light wavelength used in the MSL system). Four concentrations of Tinuvin 327 in resin were used (0.00, 0.05, 0.10, and 0.15 percent (w/w)), and cure depth experiments were performed. To investigate the effects of different concentrations of Tinuvin 327 on complex 3D microstructure fabrication, several microstructures with overhanging features such as a fan and spring were fabricated.
Findings
Results showed that higher concentrations of Tinuvin 327 reduced penetration depths and thus cure depths. For the resin with 0.15 percent (w/w) of the Tinuvin 327, a cure depth of ∼30 μm was achieved as compared to ∼200 μm without the light absorber. The four resin solutions were used to fabricate complex 3D microstructures, and different concentrations of Tinuvin 327 at a given irradiance and exposure energy were required for successful fabrication depending on the geometry of the micro‐part (concentrations of 0.05 and 0.1 percent (w/w) provided the most accurate builds for the fan and spring, respectively).
Research limitations/implications
Although two different concentrations of light absorber in solution were required to demonstrate successful fabrication for two different micro‐part geometries (a fan and spring), the experiments were performed using a single irradiance and exposure energy. A single solution with the light absorber could have possibly been used to fabricate these micro‐parts by varying irradiance and/or exposure energy, although the effects of varying these parameters on geometric accuracy, mechanical strength, overall manufacturing time, and other variables were not explored.
Originality/value
This work systematically investigated 3D microstructure fabrication using different concentrations of a light absorber in solution, and demonstrated that different light absorption characteristics were required for different down‐facing micro‐features.
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Shih‐Hsuan Chiu, Sheng‐Hong Pong, Dien‐Chi Wu and Chien‐Hung Lin
The purpose of this paper is to present a novel photomask auto‐correction method for the area‐forming rapid prototyping (RP) system.
Abstract
Purpose
The purpose of this paper is to present a novel photomask auto‐correction method for the area‐forming rapid prototyping (RP) system.
Design/methodology/approach
A digital light processing (DLP) projector was used in this research as a light source to generate the photomask image. A set of optical lenses were mounted in front of the DLP to rescale the photomask image. The rescaled photomask image was collected into a computer via a camera. By using the technique of image processing, the actual size of the photomask was then calculated. The designed size of the photomask image was eventually achieved by adjusting the relative locations of the lenses.
Findings
It was found that this proposed photomask auto‐correction method can produce a more accurate dimension of the photomask image and perform with higher efficiency than the manual calibration processes.
Originality/value
The paper is believed to be the first work to use the image‐processing technique to calibrate the photomask of an area‐forming RP system, as well as to employ a method of adjusting the relative position between the lenses to rescale the photomask image size.
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Victor A. Lifton, Gregory Lifton and Steve Simon
This study aims to investigate the options for additive rapid prototyping methods in microelectromechanical systems (MEMS) technology. Additive rapid prototyping technologies…
Abstract
Purpose
This study aims to investigate the options for additive rapid prototyping methods in microelectromechanical systems (MEMS) technology. Additive rapid prototyping technologies, such as stereolithography (SLA), fused deposition modeling (FDM) and selective laser sintering (SLS), all commonly known as three-dimensional (3D) printing methods, are reviewed and compared with the resolution requirements of the traditional MEMS fabrication methods.
Design/methodology/approach
In the 3D print approach, the entire assembly, parts and prototypes are built using various plastic and metal materials directly from the software file input, completely bypassing any additional processing steps. The review highlights their potential place in the overall process flow to reduce the complexity of traditional microfabrication and long processing cycles needed to test multiple prototypes before the final design is set.
Findings
Additive manufacturing (AM) is a promising manufacturing technique in micro-device technology.
Practical implications
In the current state of 3D printing, microfluidic and lab-on-a-chip devices for fluid handling and manipulation appear to be the most compatible with the 3D print methods, given their fairly coarse minimum feature size of 50-500 μm. Future directions in the 3D materials and method development are identified, such as adhesion and material compatibility studies of the 3D print materials, wafer-level printing and conductive materials development. One of the most important goals should be the drive toward finer resolution and layer thickness (1-10 μm) to stimulate the use of the 3D printing in a wider array of MEMS devices.
Originality/value
The review combines two discrete disciplines, microfabrication and AM, and shows how microfabrication and micro-device commercialization may benefit from employing methods developed by the AM community.