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Full-Text Articles in Mechanical Engineering

Fabrication Of Complex 3d Micro-Scale Scaffolds And Drug Delivery Devices Using Dynamic Mask Projection Microstereolithography, Jae-Won Choi, In-Baek Park, Ryan B. Wicker, Seok-Hee Lee, Ho-Chan Kim Apr 2015

Fabrication Of Complex 3d Micro-Scale Scaffolds And Drug Delivery Devices Using Dynamic Mask Projection Microstereolithography, Jae-Won Choi, In-Baek Park, Ryan B. Wicker, Seok-Hee Lee, Ho-Chan Kim

Dr. Jae-Won Choi

Microstereolithography (μSL) technology can fabricate three-dimensional (3D) tissue engineered scaffolds with controlled biochemical and mechanical micro-architectures. A μSL system for tissue engineering was developed using a Digital Micromirror Device (DMDTM) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365 nm for crosslinking the photoreactive polymer solution. The μSL system was designed with x-y resolution of ~2 μm and a vertical (z) resolution of ~1 μm. To demonstrate the use of μSL in tissue engineering, poly(propylene fumarate) (PPF) was synthesized with a molecular weight of ~1200 Da. The viscosity of the PPF was reduced to ~150 cP ...


Curing Characteristics Of 3-Dimensional Microstructures Using Dynamic Pattern Projection, Jae-Won Choi, Young-Myoung Ha, Kyung-Hyun Choi, Seok-Hee Lee Apr 2015

Curing Characteristics Of 3-Dimensional Microstructures Using Dynamic Pattern Projection, Jae-Won Choi, Young-Myoung Ha, Kyung-Hyun Choi, Seok-Hee Lee

Dr. Jae-Won Choi

Using microstereolithography technology based on dynamic pattern projection, we can fabricate micro parts with high aspect ratio. In this technology, STL file is the standard format as the same of conventional rapid prototyping system, and 3D part is fabricated by stacking layers that are sliced as 2D section from STL file. In the conventional method, the resin surface is cured as scanning laser beam spot according to the section shape, but in this research, we use projection process which enables to cure the resin surface by one irradiation. DMD is a dynamic pattern generator that makes black and white regions ...


Dmd-Based 3d Micro-Manufacturing, Jae-Won Choi, Michael Irwin, Ryan Wicker Apr 2015

Dmd-Based 3d Micro-Manufacturing, Jae-Won Choi, Michael Irwin, Ryan Wicker

Dr. Jae-Won Choi

The development of the Digital Micromirror Device (DMD) by Texas Instruments has made a significant breakthrough in 3D micro-manufacturing, and in particular, in the area of additive layer-based manufacturing. One area of particular interest for using DMD technology is microstereolithography; a technology that builds 3D shapes through successive photopolymerization of individual thin 2D layers that are stacked vertically. A DMD-based projection microstereolithography system and a robust micro-manufacturing process have been developed. This system and various micro-fabricated 3D structures with features on the order of 10 microns, including recent advancements in multimaterial micro-fabrication, will be presented and described.


Fabrication Of Embedded Horizontal Micro-Channels Using Linescan Stereolithography, Jae-Won Choi, Rolando Quintana, Ryan Wicker Apr 2015

Fabrication Of Embedded Horizontal Micro-Channels Using Linescan Stereolithography, Jae-Won Choi, Rolando Quintana, Ryan Wicker

Dr. Jae-Won Choi

The objective of this paper is to demonstrate a method for producing embedded horizontal micro-channels using a commercial line-scan stereolithography (SL) system. To demonstrate that the method is repeatable, reproducible and capable of producing accurate horizontal micro-channels, a statistical design of experiments was performed. Design/methodology/approach – Demonstration of the technique was performed using a 3D Systems Viper si2TM SL system and DSM Somos® WaterShedTM resin with polytetrafluoroethylene (PTFE)-coated wire having diameters of 31.6 and 57.2 μm. By embedding the wire and building around the insert, the down-facing surfaces were supported during fabrication enabling accurate fabrication of ...


Fabrication And Characterization Of Embedded Horizontal Micro‐Channels Using Line‐Scan Stereolithography, Jae-Won Choi, Rolando Quintana, Ryan Wicker Apr 2015

Fabrication And Characterization Of Embedded Horizontal Micro‐Channels Using Line‐Scan Stereolithography, Jae-Won Choi, Rolando Quintana, Ryan Wicker

Dr. Jae-Won Choi

– The objective of this paper is to demonstrate a method for producing embedded horizontal micro‐channels using a commercial line‐scan stereolithography (SL) system. To demonstrate that the method is repeatable, reproducible and capable of producing accurate horizontal micro‐channels, a statistical design of experiments was performed.


Cure Depth Control For Complex 3d Microstructure Fabrication In Dynamic Mask Projection Microstereolithography, Jae-Won Choi, Ryan Wicker, Seok-Hyun Cho, Chang-Sik Ha, Seok-Hee Lee Apr 2015

Cure Depth Control For Complex 3d Microstructure Fabrication In Dynamic Mask Projection Microstereolithography, Jae-Won Choi, Ryan Wicker, Seok-Hyun Cho, Chang-Sik Ha, Seok-Hee Lee

Dr. Jae-Won Choi

– 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.


Scheduling And Process Planning For Multiple Material Stereolithography, Hochan Kim, Jae-Won Choi, Ryan Wicker Apr 2015

Scheduling And Process Planning For Multiple Material Stereolithography, Hochan Kim, Jae-Won Choi, Ryan Wicker

Dr. Jae-Won Choi

– To operate a multiple material stereolithography (MMSL) system, a material build schedule is required. The purpose of this paper is to describe a scheduling and process‐planning software system developed for MMSL and designed to minimize the number of material changeovers by using low‐viscosity resins that do not require sweeping.


Force And Slip Detection With Direct-Write Compliant Tactile Sensors Using Multi-Walled Carbon Nanotube/Polymer Composites, Morteza Vatani, Erik Engeberg, Jae-Won Choi Apr 2015

Force And Slip Detection With Direct-Write Compliant Tactile Sensors Using Multi-Walled Carbon Nanotube/Polymer Composites, Morteza Vatani, Erik Engeberg, Jae-Won Choi

Dr. Jae-Won Choi

A mechanically compliant tactile sensor has been developed through direct-write (DW) deposition of a flexible conductive nanocomposite embedded between flexible polyurethane materials. Dispersion of multi-walled carbon nanotubes (MWCNTs) in a flexible and photocurable monomer introduced electrical and piezoresistive properties to the polymer which was used for the flexible conductive nanocomposite. Dispensing experiments were performed using the developed DW system to precisely create and embed the sensor elements between polyurethane substrates. From the experimental results, several flexible sensors including highly stretchable sensor elements (wires) were fabricated. Experiments were also performed to show that the sensor could detect applied forces at distinct ...


Direct-Write/Cure Conductive Polymer Nanocomposites For 3d Structural Electronics, Yanfeng Lu, Morteza Vatani, Jae-Won Choi Apr 2015

Direct-Write/Cure Conductive Polymer Nanocomposites For 3d Structural Electronics, Yanfeng Lu, Morteza Vatani, Jae-Won Choi

Dr. Jae-Won Choi

The use of direct-write (DW) in the fabrication of conductive structures offers dramatic benefits over traditional technologies in terms of low-cost, print-on-demand conformal manufacturing. This DW process can be combined with direct-cure (DC) process as one-step manufacturing of conducting elements, whereas conventional methods need a manufacturing process of conducting elements followed by a relatively long time post-curing/baking process. A hybrid technology combined with direct-write/cure (DWC) and projection microstereolithography (PμSL) is presented in this work. Carbon nanotubes (CNTs) were dispersed in a photopolymer solution to introduce conductivity. The developed PμSL was used to create 3D structures, and DWC of ...


Improvement Of Mechanical Properties Of Uv-Curable Resin For High-Aspect Ratio Microstructures Fabricated In Microstereolithography, Su-Do Lee, Jae-Won Choi, In-Baek Park, Chang-Sik Ha, Seok-Hee Lee Apr 2015

Improvement Of Mechanical Properties Of Uv-Curable Resin For High-Aspect Ratio Microstructures Fabricated In Microstereolithography, Su-Do Lee, Jae-Won Choi, In-Baek Park, Chang-Sik Ha, Seok-Hee Lee

Dr. Jae-Won Choi

Recently, microstructures fabricated using microstereolithography technology have been used in the biological, medical and mechanical fields. Microstereolithography can fabricate real 3D microstructures with fine features, although there is presently a limited number of materials available for use in the process. Deformation of the fine features on a fabricated microstructure remains a critical issue for successful part fabrication, and part deformation can occur during rinsing or during fabrication as a result of fluid flow forces that occur during movement of mechanical parts of the system. Deformation can result in failure to fabricate a particular feature by breaking the feature completely, spatial ...


A Study On Enhancement Of Human Sensitivity For Interior Of Prototype Vehicles, Jae-Won Choi, Hwa-Jun Yang, S. H. Lee Apr 2015

A Study On Enhancement Of Human Sensitivity For Interior Of Prototype Vehicles, Jae-Won Choi, Hwa-Jun Yang, S. H. Lee

Dr. Jae-Won Choi

No abstract provided.


Slice Overlap-Detection Algorithm For Process Planning In Multiple-Material Stereolithography, Ho-Chan Kim, Jae-Won Choi, Eric Macdonald, Ryan Wicker Apr 2015

Slice Overlap-Detection Algorithm For Process Planning In Multiple-Material Stereolithography, Ho-Chan Kim, Jae-Won Choi, Eric Macdonald, Ryan Wicker

Dr. Jae-Won Choi

Recently, a multiple-material stereolithography (MMSL) system was introduced, which included the novel feature of stacking different photocurable resins to produce a multiple-material part. This process is capable of fabricating intricately detailed parts with smooth surface finish and internal structures of various colors. However, the MMSL system requires a washing process when switching materials, and this additional step increases the fabrication time and also introduces deformations in the build structure as registration errors accumulate. Consequently, reducing the number of material changeovers in this process is a priority, and the minimum number of changeovers is imposed in part by the sweep interference ...


Fabrication Of 3-Dimensional Microstructures Using Dynamic Image Projection, Jae-Won Choi, Y. Ha, K. Choi, Seok Lee Apr 2015

Fabrication Of 3-Dimensional Microstructures Using Dynamic Image Projection, Jae-Won Choi, Y. Ha, K. Choi, Seok Lee

Dr. Jae-Won Choi

As demand for complex precision parts increase, the existing fabrication methods such as MEMS, and LIGA technology have technical limitations with regard to high precision, high aspect ratio, and high complexity. A microstereolithography technology based on DMDTM(Digital Micromirror Device) can meet these demands. DMD enables a system to handle dynamic patterns. In this technology, the same standard format of the conventional rapid prototyping system, the STL file, is used, and 3D parts are fabricated by stacking layers that are sliced as 2D section from STL file. Whereas in conventional methods, the resin surface is cured by scanning laser beam ...


Combined Micro And Macro Additive Manufacturing Of A Swirling Flow Coaxial Phacoemulsifier Sleeve With Internal Micro-Vanes, Jae-Won Choi, Masaki Yamashita, Jun Sakakibara, Yuichi Kaji, Tetsuro Oshika, Ryan Wicker Apr 2015

Combined Micro And Macro Additive Manufacturing Of A Swirling Flow Coaxial Phacoemulsifier Sleeve With Internal Micro-Vanes, Jae-Won Choi, Masaki Yamashita, Jun Sakakibara, Yuichi Kaji, Tetsuro Oshika, Ryan Wicker

Dr. Jae-Won Choi

Microstereolithography (µSL) technology can fabricate complex, three-dimensional (3D) microstructures, although µSL has difficulty producing macrostructures with micro-scale features. There are potentially many applications where 3D micro-features can benefit the overall function of the macrostructure. One such application involves a medical device called a coaxial phacoemulsifier where the tip of the phacoemulsifier is inserted into the eye through a relatively small incision and used to break the lens apart while removing the lens pieces and associated fluid from the eye through a small tube. In order to maintain the eye at a constant pressure, the phacoemulsifier also includes an irrigation solution ...


Direction Of Slip Detection For A Biomimetic Tactile Sensor, Erik Engeberg, Morteza Vatani, Jae-Won Choi Apr 2015

Direction Of Slip Detection For A Biomimetic Tactile Sensor, Erik Engeberg, Morteza Vatani, Jae-Won Choi

Dr. Jae-Won Choi

A biomimetic tactile sensor (BTS) is developed from strips of electrically conductive carbon nanotubes (CNTs) mixed in a polymer matrix that is embedded within a flexible polyurethane shell. The mechanical compliance of the BTS is similar to the human fingertip. Experiments are performed which show that the BTS can be used to detect slip and the direction that slip occurs by examining the relative timing among force signals from adjacent strips of CNTs and the frequency content of the force signals. The BTS can also detect forces applied at distinct points on the surface of the BTS.


Development Of A Mobile Fused Deposition Modeling System With Enhanced Manufacturing Flexibility, Jae-Won Choi, Francisco Medina, Chiyen Kim, David Espalin, David Rodriguez, Brent Stucker, Ryan Wicker Apr 2015

Development Of A Mobile Fused Deposition Modeling System With Enhanced Manufacturing Flexibility, Jae-Won Choi, Francisco Medina, Chiyen Kim, David Espalin, David Rodriguez, Brent Stucker, Ryan Wicker

Dr. Jae-Won Choi

Development of a flexible and mobile fused deposition modeling (FDM) system from an existing FDM system to enable deposition of material on virtually any surface without being confined to a build chamber is described. Flexibility of the system was demonstrated by depositing ABS on different surfaces, and simple pull tests were performed to determine bonding strength between the deposited materials. To develop the flexible FDM system, a Stratasys FDM 3000 machine was used and modified by reversing the z stage and attaching the x–y table controlling the FDM head to the bottom of the z stage. In this new ...


Development Of A Multi-Material Stereolithography System, Ho-Chan Kim, Jae-Won Choi, Ryan B. Wicker Apr 2015

Development Of A Multi-Material Stereolithography System, Ho-Chan Kim, Jae-Won Choi, Ryan B. Wicker

Dr. Jae-Won Choi

Researchers continue to explore possibilities for expanding additive manufacturing (AM) technologies into direct product manufacturing. One limitation is in the materials available for use in AM that can meet the needs of end-use applications. Stereolithography (SL) is an AM technology well known for its precision and high quality surface finish capabilities. SL builds parts by selectively crosslinking or solidifying photo-curable liquid resins, and the resin industry has been continuously developing new resins with improved performance characteristics. This paper introduces a unique SL machine that can fabricate parts out of multiple SL materials. The technology is based on using multiple vats ...


Fabrication Of Part And Its Evaluation Using Dual Laser In Solid Freeform Fabrication System, Jae-Won Choi, Dong-Soo Kim, Yang-Hoe Doh, Seok-Hee Lee, Kyung-Hyun Choi Apr 2015

Fabrication Of Part And Its Evaluation Using Dual Laser In Solid Freeform Fabrication System, Jae-Won Choi, Dong-Soo Kim, Yang-Hoe Doh, Seok-Hee Lee, Kyung-Hyun Choi

Dr. Jae-Won Choi

A solid freeform fabrication (SFF) system using selective laser sintering (SLS) is currently recognized as a leading process and the SLS extends the applications to machinery and automobiles due to various employing materials. In order to fabricate a large part with SFF system, dual laser approach has been introduced. Since the building room is divided into two regions, each scan path for dual laser system is generated based on the single laser scan path. Scan paths for each laser have to be synchronized and consider mechanical strength against fracture at the interfaced region. This paper will address generation of single ...


Effects Of Build Orientation On Tensile Strength For Stereolithography-Manufactured Astm D-638 Type I Specimens, Rolando Quintana, Jae-Won Choi, Karina Puebla, Ryan Wicker Apr 2015

Effects Of Build Orientation On Tensile Strength For Stereolithography-Manufactured Astm D-638 Type I Specimens, Rolando Quintana, Jae-Won Choi, Karina Puebla, Ryan Wicker

Dr. Jae-Won Choi

A statistical design of experiments (DOE) approach was used to determine if specific build orientation parameters impacted mechanical strength of stereolithography (SL) fabricated parts. A single platform (25.4 × 25.4-cm cross-section) on the 3D Systems Viper si2 SL machine was designed to hold 18 ASTM D-638 type I samples manufactured in different orientations. The DOE tested three factors: axis, layout, and position. Samples were fabricated parallel with the x-axis or y-axis, or 45° to both axes (called axes 1, 2, and 3, respectively). For each axis, samples were fabricated either flat or on an edge relative to ...


Design Of Microstereolithography System Based On Dynamic Image Projection For Fabrication Of Three-Dimensional Microstructures, Jae-Won Choi, Young Ha, Seok Lee, Kyun Choi Apr 2015

Design Of Microstereolithography System Based On Dynamic Image Projection For Fabrication Of Three-Dimensional Microstructures, Jae-Won Choi, Young Ha, Seok Lee, Kyun Choi

Dr. Jae-Won Choi

As demands for complex microstructures with high aspect ratios have increased, the existing methods, MEMS and LIGA, have had difficulties coping with the number of masks and fabricable heights. A microstereolithography technology can meet these demands because it has no need of masks and is capable of fabricating high aspect ratio microstructures. In this technology, 3D part is fabricated by stacking layers, 2D sections, which are sliced from STL file, and the Dynamic Image Projection process enables the resin surface to be cured by a dynamic image generated with DMD™ (Digital Micromirror Device) and one irradiation. In this paper, we ...


Direct-Write Stretchable Sensors Using Singlewalled Carbon Nanotubes/Polymer Matrix, Morteza Vatani, Yanfeng Lu, Kye-Shin Lee, Ho-Chan Kim, Jae-Won Choi Apr 2015

Direct-Write Stretchable Sensors Using Singlewalled Carbon Nanotubes/Polymer Matrix, Morteza Vatani, Yanfeng Lu, Kye-Shin Lee, Ho-Chan Kim, Jae-Won Choi

Dr. Jae-Won Choi

There have been increasing demands and interests in stretchable sensors with the development of flexible or stretchable conductive materials. These sensors can be used for detecting large strain, 3D deformation, and a free-form shape. In this work, a stretchable conductive sensor has been developed using single-walled carbon nanotubes (SWCNTs) and monofunctional acrylate monomers (cyclic trimethylolpropane formal acrylate and acrylate ester). The suggested sensors have been fabricated using a screw-driven microdispensing direct-write (DW) technology. To demonstrate the capabilities of the DW system, effects of dispensing parameters such as the feed rate and material flow rate on created line widths were investigated ...


Fabrication Of 3d Biocompatible/Biodegradable Micro-Scaffolds Using Dynamic Mask Projection Microstereolithography, Jae-Won Choi, Ryan Wicker, Seok-Hee Lee, Kyung-Hyun Choi, Chang-Sik Ha, Ildoo Chung Apr 2015

Fabrication Of 3d Biocompatible/Biodegradable Micro-Scaffolds Using Dynamic Mask Projection Microstereolithography, Jae-Won Choi, Ryan Wicker, Seok-Hee Lee, Kyung-Hyun Choi, Chang-Sik Ha, Ildoo Chung

Dr. Jae-Won Choi

Microstereolithography (μSL) technology can fabricate three-dimensional (3D) tissue engineered scaffolds with controlled biochemical and mechanical micro-architectures. A μSL system for tissue engineering was developed using a Digital Micromirror Device (DMD™) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365 nm for crosslinking the photoreactive polymer solution. The μSL system was designed with x–y resolution of ∼2 μm and a vertical (z) resolution of ∼1 μm. To demonstrate the use of μSL in tissue engineering, poly(propylene fumarate) (PPF) was synthesized with a molecular weight of ∼1200 Da. The viscosity of the PPF was reduced to ∼150 ...


Detection Of The Position, Direction And Speed Of Sliding Contact With A Multi-Layer Compliant Tactile Sensor Fabricated Using Direct-Print Technology, Morteza Vatani, Erik Engeberg, Jae-Won Choi Apr 2015

Detection Of The Position, Direction And Speed Of Sliding Contact With A Multi-Layer Compliant Tactile Sensor Fabricated Using Direct-Print Technology, Morteza Vatani, Erik Engeberg, Jae-Won Choi

Dr. Jae-Won Choi

A multi-layer resistance based compliant tactile sensor was fabricated using direct-print (DP) and soft molding processes. The sensor consists of two layers of embedded stretchable sensing elements sandwiched by three layers of a polyurethane rubber material. The sensing elements were created by the DP process using a photopolymer filled with multi-wall carbon nanotubes, which exhibit the property of piezoresistivity. The printed sensing elements were fully cured using ultraviolet light. The sensing elements within each layer of the sensor structure change in electrical resistance when external forces are applied. By processing the measured sensor signals, the fabricated sensor was able to ...


Multi-Material Stereolithography, Jae-Won Choi, Ho-Chan Kim, Ryan Wicker Apr 2015

Multi-Material Stereolithography, Jae-Won Choi, Ho-Chan Kim, Ryan Wicker

Dr. Jae-Won Choi

A multi-material stereolithography (MMSL) machine was developed by retrofitting components from a commercial 3D Systems 250/50 stereolithography (SL) machine on a separate stand-alone system and adapting the components to function with additional components required for MMSL operation. The MMSL machine required construction of a new frame and the development of a new rotating vat carousel system, platform assembly, and automatic leveling system. The overall operation of the MMSL system was managed using a custom LabVIEW® program, which included controlling a new vat leveling system and new linear and rotational stages, while the commercial SL control software (3D Systems Buildstation ...


Direct-Write Of Multi-Layer Tactile Sensors, Jae-Won Choi, Morteza Vatani, Erik Engeberg Apr 2015

Direct-Write Of Multi-Layer Tactile Sensors, Jae-Won Choi, Morteza Vatani, Erik Engeberg

Dr. Jae-Won Choi

Direct-write of piezoresistive photopolymers is regarded as a promising means to produce compliant tactile sensors. In this work, a multi-layer compliant tactile sensor was developed using a hybrid manufacturing process including soft molding, micro-dispensing and photopolymerization processes. The working principle of the suggested sensor is to detect changes in resistance as it is deformed. A compliant skin structure was built layer-by-layer using a soft polyurethane material to cover the piezoresistive sensing elements. These sensing elements were created from stretchable photocurable conductive carbon nanotube (CNT)/prepolymer nanocomposites, which were deposited by the micro-dispensing process within the polyurethane skin layers and cured ...


Fabrication Of Microstructure Array Using The Projection Microstereolithography System, Jae-Won Choi, Young-Myoung Ha, Seok-Hee Lee Apr 2015

Fabrication Of Microstructure Array Using The Projection Microstereolithography System, Jae-Won Choi, Young-Myoung Ha, Seok-Hee Lee

Dr. Jae-Won Choi

Microstereolithography technology is similar to the conventional stereolithography process and enables to fabricate a complex 3D microstructure. This is divided into scanning and projection type according to aiming at precision and fabrication speed. The scanning MSL fabricates each layer using position control of laser spot on the resin surface, whereas the projection MSL fabricates one layer with one exposure using a mask. In the projection MSL, DMD used to generate dynamic pattern consists of micromirrors which have per side. The fabrication range and resolution are determined by the field of view of the DMD and the magnification of the projection ...


Free-Form Surface Generation From Measuring Points Using Laser Scanner, Jae-Won Choi, Sugn-Min Hur, Seok-Hee Lee Apr 2015

Free-Form Surface Generation From Measuring Points Using Laser Scanner, Jae-Won Choi, Sugn-Min Hur, Seok-Hee Lee

Dr. Jae-Won Choi

With the development of a laser scanner of high precision and increased speed, reverse engineering becomes a key approach to reduce the time for the development of new products. But the modeling process is not so automated enough until now.Modeling in real workshops is usually performed by the experienced operators and it requires a skillful technique to get the resultant surface of high quality and precision. In this paper, a systematic solution is proposed to automate the free-form surface generation from the measured point data. Compatibility is imposed to the measured point data during input curve generation. And the ...


Multiple Fabrications Of Sacrificial Layers To Enhance The Dimensional Accuracy Of Microstructures In Maskless Projection Microstereolithography, In-Baek Park, Jae-Won Choi, Young-Myoung Ha, Seok-Hee Lee Apr 2015

Multiple Fabrications Of Sacrificial Layers To Enhance The Dimensional Accuracy Of Microstructures In Maskless Projection Microstereolithography, In-Baek Park, Jae-Won Choi, Young-Myoung Ha, Seok-Hee Lee

Dr. Jae-Won Choi

Microstereolithography (MSL) is a promising technology for producing fully three-dimensional microstructures with overhanging features and high-aspect ratios. In conventional stereolithography (SL), a layer thickness of ≈50–100 μm is obtained by using a recoater. However, a recoater cannot be used in MSL, where the layer thickness is typically ≈10 μm or less, since resin flow may break or distort the pre-fabricated layers. In most MSL systems, the resin surface (or layer thickness) is controlled by a free surface technique that employs resin gravity to refresh the resin surface over a given settling time. In addition, a sacrificial layer must be ...


Development Of Direct Printing/Curing Process For 3d Structural Electronics, Yanfeng Lu, Morteza Vatani, Ho-Chan Kim, Rae-Chan Lee, Jae-Won Choi Apr 2015

Development Of Direct Printing/Curing Process For 3d Structural Electronics, Yanfeng Lu, Morteza Vatani, Ho-Chan Kim, Rae-Chan Lee, Jae-Won Choi

Dr. Jae-Won Choi

3D structural electronics is a new paradigm in fabricating electronics with high design complexity. Basically, manufacturing of 3D structural electronics consists of several processes: structure building, wire creation, and pick-and-place of electrical components. In this work, a 3D structure was built in a commercial AM machine, and conductive wires were created on the 3D structure with a predetermined design of an electronic circuit. Generally, 2D wire paths are projected to a 3D surface, and a tool path for the wire is generated in advance. And a direct printing device follows the tool path to draw the conductive wires on the ...


Numerical And Experimental Analysis Of Droplet Impact, Deformation And Formation Of Droplet Train, Muhammad Hasan, Morteza Vatani, Yanfeng Lu, Ho-Chan Kim, Jae-Won Choi Apr 2015

Numerical And Experimental Analysis Of Droplet Impact, Deformation And Formation Of Droplet Train, Muhammad Hasan, Morteza Vatani, Yanfeng Lu, Ho-Chan Kim, Jae-Won Choi

Dr. Jae-Won Choi

Numerical analysis for a two dimensional case of two–phase fluid flow has been performed to investigate droplet impact, deformation for a droplet train. The purpose of this investigation is to study the phenomenon of liquid droplet impact on a liquid film created by a flattened droplet and the consequent deformation of the film while merging and advancing of the moving front of the film, during the manufacturing processes with jetting technology such as a direct printing process and inkjet printing. This investigation focuses on the analysis of interface tracking and the change of shape for an impacted droplet of ...