Jae-Won Choi

Bio: Jae-Won Choi is an academic researcher from University of Akron. The author has contributed to research in topics: Tactile sensor & Piezoresistive effect. The author has an hindex of 26, co-authored 122 publications receiving 2208 citations. Previous affiliations of Jae-Won Choi include University of Texas at El Paso & Pusan National University.

A review on 3D printed smart devices for 4D printing

Abstract: Multi-material 3D printing with electrically functional materials including conducting, sensing, insulating and semiconducting materials has led to the development of smart devices such as 3D structural electronics, sensors, batteries, etc. Electronically smart devices are a hot issue in 3D printing because they can certainly benefit from 3D printing technology, providing high design flexibility and customized functions. Shape-changing materials (e.g. shape memory polymers) incorporated in 3D printing have given birth to 4D printing, where 3D printed structures change in their shapes by external stimuli (temperature, light, water, etc.). The motivation of this review paper is to discuss mutual benefits from both 3D printed smart devices and 4D printed features, which can be built in a single body. It is expected that the combination of 3D printed smart devices and 4D printing would contribute to the development of high performance, adaptability to the environment and programmable 3D smart devices, which have not yet existed. This paper has reviewed the background of 3D printing, smart device fabrication using 3D printing, development into 4D printing, and future applications of 4D printing.

Arbitrary Photo-Patterning in Liquid Crystal Alignments Using DMD Based Lithography System

Abstract: We propose and implement a technique for arbitrary pattern fabrication in liquid crystal (LC) alignments and local polarization control for light wavefront. A micro-lithography system with a digital micro-mirror device as dynamic mask forms arbitrary micro-images on photoalignment layers and further guides the LC molecule orientations. Besides normal phase gratings, more complex 2D patterns such as quasicrystal and checkerboard structures are demonstrated. To characterize the optical performances of the fabricated structures, the electro-optically tunable diffraction patterns and efficiencies are demonstrated in several 1D/2D phase gratings. Compared to other techniques, our method enables the arbitrary and instant manipulation of LC alignments and light polarization states, facilitating wide applications in display and photonic fields.

Multi-material microstereolithography.

Abstract: We have previously described the development of a microstereolithography (µSL) system using a Digital Micromirror Device (DMD) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365 nm for crosslinking a photoreactive polymer solution. The µSL system was designed with x–y resolution of approximately 2 µm and a vertical (z) resolution of approximately 1 µm (with practical build limitations on vertical resolution of approximately 30 µm due to limitations on controlling UV penetration in z). The developed µSL system is capable of producing real three-dimensional (3D) microstructures, which can be employed in applications such as microfluidics, tissue engineering, and various functional microsystems. Many benefits will potentially be derived from producing multiple material microstructures in µSL, and one particular application area of interest is in producing multi-material microscaffolds for tissue engineering. In the present work, a method for multi-material µSL fabrication was developed using a syringe pump system to add a material to a small, removable vat designed specifically for the multi-material µSL system. Multi-material fabrication was accomplished using a material changeover process that included manually removing the vat, draining the current material, rinsing the vat, returning the vat to the system, and finally dispensing a prescribed volume in the vat using the syringe pump. Layer thicknesses of approximately 30 µm were achieved using this process. To demonstrate this system, several multi-material microstructures were produced to highlight the capability of this promising technology for fabricating 3D functional, multi-material microstructures with spatial control over placement of both material and structure.

Cure depth control for complex 3D microstructure fabrication in dynamic mask projection microstereolithography

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 cur...

The Design and Analysis of Experiments

Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

A Review of Additive Manufacturing

Abstract: Additive manufacturing processes take the information from a computer-aided design (CAD) file that is later converted to a stereolithography (STL) file. In this process, the drawing made in the CAD software is approximated by triangles and sliced containing the information of each layer that is going to be printed. There is a discussion of the relevant additive manufacturing processes and their applications. The aerospace industry employs them because of the possibility of manufacturing lighter structures to reduce weight. Additive manufacturing is transforming the practice of medicine and making work easier for architects. In 2004, the Society of Manufacturing Engineers did a classification of the various technologies and there are at least four additional significant technologies in 2012. Studies are reviewed which were about the strength of products made in additive manufacturing processes. However, there is still a lot of work and research to be accomplished before additive manufacturing technologies become standard in the manufacturing industry because not every commonly used manufacturing material can be handled. The accuracy needs improvement to eliminate the necessity of a finishing process. The continuous and increasing growth experienced since the early days and the successful results up to the present time allow for optimism that additive manufacturing has a significant place in the future of manufacturing.

Evaluation of 3D printing and its potential impact on biotechnology and the chemical sciences.

Abstract: Nearing 30 years since its introduction, 3D printing technology is set to revolutionize research and teaching laboratories. This feature encompasses the history of 3D printing, reviews various printing methods, and presents current applications. The authors offer an appraisal of the future direction and impact this technology will have on laboratory settings as 3D printers become more accessible.