May 15, 2020 by admin 0 Comments

Exfoliated graphene/thermoplastic elastomer nanocomposites with improved wear properties for 3D printing

Authors
Hyerin Jeon a,b,1, Youn Kim b,1, Woong-Ryeol Yu a, Jea UkLee b
Abstract
Although three-dimensional (3D) thermoplastic elastomer printing has been studied, the unsatisfactory mechanical properties of 3D-printed elastomers, especially their substandard wear characteristics, make it difficult to use them in industrial products or processes. In this study, thermoplastic elastomer nanocomposites with improved wear properties were fabricated using thermoplastic polyether elastomer (TPEE), with surface-modified carbon black (CB), or electrochemically exfoliated graphene through multiple extrusion processes. The surface-modified CB/TPEE composite showed about four times more wear resistance and 26% improvement in tensile strength as compared to bare TPEE resin. The graphene/TPEE composite with only 1 wt% graphene exhibited an elevenfold increase in wear resistance and 43% improvement in the tensile strength owing to the high dispersibility and lubricating effect of the two-dimensional graphene filler. Graphene/TPEE composites were extruded into filaments for 3D printing. Three-dimensional printed products made from the nanocomposites have much higher wear resistance than 3D products of bare TPEE resin, demonstrating that graphene and TPEE nanocomposites are well suited for manufacturing a wide variety of complex electronic and mechanical components with excellent wear characteristics.

January 6, 2020 by admin 0 Comments

NiCHE Platform: Nature-Inspired Catechol-Conjugated Hyaluronic Acid Environment Platform for Salivary Gland Tissue Engineering

Authors
Sang-woo Lee, Ji Hyun Ryu, Min Jae Do, Eun Namkoong, Haeshin Lee* and Kyungpyo Park*
Abstract
Recently, there has been growing interest in replacing severely damaged salivary glands with artificial salivary gland functional units created in vitro by tissue engineering approaches. Although various materials such as poly(lactic-co-glycolic acid), polylactic acid, poly(glycolic acid), and polyethylene glycol hydrogels have been used as scaffolds for salivary gland tissue engineering, none of them is effective enough to closely recapitulate the branched structural complexity and heterogeneous cell population of native salivary glands. Instead of discovering new biomaterial candidates, we synthesized hyaluronic acid–catechol (HACA) conjugates to establish a versatile hyaluronic acid coating platform named “NiCHE (nature-inspired catechol-conjugated hyaluronic acid environment)” for boosting the salivary gland tissue engineering efficacy of the previously reported biomaterials. By mimicking hyaluronic acid-rich niche in the mesenchyme of embryonic submandibular glands (eSMGs) with NiCHE coating on substrates including polycarbonate membrane, stiff agarose hydrogel, and polycaprolactone scaffold, we observed significantly enhanced cell adhesion, vascular endothelial and progenitor cell proliferation, and branching of in vitro-cultured eSMGs. High mechanical stiffness of the substrate is known to inhibit eSMG growth, but the NiCHE coating significantly reduced such stiffness-induced negative effects, leading to successful differentiation of progenitor cells to functional acinar and myoepithelial cells. These enhancement effects of the NiCHE coating were due to the increased proliferation of vascular endothelial cells via interaction between CD44 and surface-immobilized HAs. As such, our NiCHE coating platform renders any kind of material highly effective for salivary gland tissue culture by mimicking in vivo embryonic mesenchymal HA. Based on our results, we expect the NiCHE coating to expand the range of biomaterial candidates for salivary glands and other branching epithelial organs.

June 1, 2019 by admin 0 Comments

Characterization of the biomechanical properties of canine trachea using a customized 3D-printed apparatus

Authors
Jennifer Sang-jee Lee (a, 1), Jonghyun Park (b, 1), Dong-A Shin (b), Yoon-jong Ryu (a), Hee Chan Kim (c, d, e), Jung Chan Lee (c, d, e), Seong Keun Kwon (a)
Abstract
Objectives The canine trachea is considered to be an excellent preclinical model for tracheal research due to its similar mechanical and dimensional characteristics to the human trachea. However, normative biomechanical properties have yet to be defined and it is one of the main reasons tracheal reconstruction has not succeeded in animal models at large scale. Variation and inaccurate measurement due to a lack of proper apparatus for mechanical tests further prevent determination of normative mechanical data of the trachea. The goal of this study was to overcome these shortcomings by designing the measuring apparatus using 3D-printing technology. Using this apparatus, we determined the normative biomechanical properties of the canine trachea. Methods Whole tracheas were obtained from thirteen mongrel dogs. Biomechanical measurements were performed to determine the radial compressive strength and tensile strength of the intact trachea, and the elastic modulus of the tracheal cartilage. Results Structural parameter data indicated the canine trachea to have inner-diameters similar to those of the human trachea and other widely used animal models. The compressive strength was 4.24 N while the tensile strength was 29.96 N. The elastic modulus of the cartilage portion of the trachea was 1.58 N without showing a significant difference in value based on the location of the trachea. Conclusions This study delineates a comprehensive and foundational characterization of the biomechanical properties of both the intact and cartilage portion of the canine trachea. The parameters were in agreement with those of the human trachea, confirming the canine trachea to be an excellent preclinical model for tracheal research.

February 1, 2019 by admin 0 Comments

Effect of Temperature on the Emission Rate of Particulate Matter during 3D Printing and Characteristics of Initial Peak

Authors
Haejoon Jeon
Abstract
Three dimensional (3D) printers based on fused deposition modeling (FDM) technology are rapidly becoming popular. Various harmful substances including gas and particulate matter are known to be released during 3D printing by heating thermoplastic materials at high temperature conditions. Previous study reported that the particle concentration increased as the temperature rising and occurred highest emission at early stages of printing although limited paper mentioned about the effect of temperature on the particle emission and the high concentration of the early printing. The aims of this study were to evaluate the effect of temperature on the emission rate of particulate matter during three-dimensional (3D) printing using different filament types and to investigate the mechanism of the highest concentration peak in early stage of printing.

February 1, 2019 by admin 0 Comments

3D printed PLCL/hydrogel complex scaffolds using decellularized adipose tissue development

Authors
Soojin Lee
Abstract
Adipose tissue regeneration has been studied for many patients who had a burn defect, traumatic injury and mastectomy to improve their quality of life. The number of surgical operations is increasing due to the increase in the number of patients newly diagnosed with breast cancer. Although the studies on adipose tissue regeneration using natural polymer and synthetic polymer have been done, but disadvantages such as fast degradation rate and mismatch of mechanical properties still exist. So we set up three strategies to overcome the limits of previous researches. First, poly (lactide-co-caprolactone) (PLCL), very elastic and biocompatible polymer, was synthesized to provide proper mechanical properties and three dimensional structure for adipose tissue engineering. It also provide a stable tertiary structure to prevent the fast degradation while the adipose tissue regenerate. Secondly, to induce adipogenic differentiation and neo-vascularization for large sized tissue, decellularized extracellular matrix (dECM) was used to promote angiogenesis for efficient blood supply. Lastly, 3D printing technique was used to fabricate a patient-specific scaffold.<br /> The PLCL and adipose tissue derived dECM hydrogel was printed through dual nozzle system and the complex construct composed of PLCL and hydrogel was fabricated (15 mm x 15 mm x 4.0 mm). Flexibility and stretchability of the PLCL copolymer were maintained after 3D printing. Adipose tissue derived dECM based hydrogel was prepared as a biocompatible bioink. Since 1:3-adECM: collagen showed the best cell viability and printability than other ratio of hydrogels, it was used for further experiments. We evaluated angiogenesis and macrophage infiltration of the samples while in vivo experiments and investigated the potential for adipose tissue regeneration. A lot of matured blood vessels were observed more in the Hydrogel-PLCL complex constructs than in PLCL only scaffolds. Moreover, the higher expression of M2 macrophage for tissue repair and of adipogenic differentiation relative genes was measured in the Hydrogel-PLCL complex constructs by immunofluorescent analysis and real-time PCR, respectively. Based on these results, we anticipate that our constructs will be a promising alternative for adipose tissue regeneration.

August 30, 2017 by admin 0 Comments

Characterization and Control of Nanoparticle Emission during 3D Printing

Authors
Ohhun Kwon †‡, Chungsik Yoon *†‡, Seunghon Ham ‡, Jihoon Park †, Jinho Lee †, Danbi Yoo †, Yoojin Kim †
Abstract
This study aimed to evaluate particle emission characteristics and to evaluate several control methods used to reduce particle emissions during three-dimensional (3D) printing. Experiments for particle characterization were conducted to measure particle number concentrations, emission rates, morphology, and chemical compositions under manufacturer-recommended and consistent-temperature conditions with seven different thermoplastic materials in an exposure chamber.

July 11, 2017 by admin 0 Comments

A portable, low-cost, 3D-printed main magnetic field system for magnetic imaging

Authors
Iksung Kang
Abstract
In this paper, a portable, low-cost, 3D-printed system for main magnetic field is proposed to suggest a solution for accessibility problems of current magnetic imaging systems, e.g. MRI scanner, their size and cost. The system consists of twelve pairs of NdFeB N35 permanent magnets arranged in a Halbach array in a 3D-printed, cylindrical container based on FEM simulation results by COMSOL Multiphysics 4.4b. Its magnetic field homogeneity and field strength were measured by Hall sensors, WSH-135 XPAN2 by Wilson Semiconductor, and the container was printed by 3DISON H700 by Rokit. The system generated a 5-mm imaging quality FOV and main magnetic field of 120 mT with a 12 % error in the field strength. Also, a hundred dollar was enough for the manufacture of the system with a radius of 6 cm and height of 10 cm. Given the results, I believe the system will be useful for some magnetic imaging applications, e.g. EPRI and low-field MRI.

October 18, 2016 by admin 0 Comments

Development of a Multi-functional Soft Robot (SNUMAX) and Performance in RoboSoft Grand Challenge

Authors
Jun-Young Lee, Brian Byunghyun Kang, Dae-Young Lee, Sang-Min Baek, Woong-Bae Kim, Woo-Young Choi, Jeong-Ryul Song, Hyeong-Joon Joo, Daegeun Park, Kyu-Jin Cho*
Abstract
This paper introduces SNUMAX, the grand winner of the RoboSoft Grand Challenge. SNUMAX was built to complete all the tasks of the challenge. Completing these tasks required robotic compliant components that could adapt to variable situations and environments and generate enough stiffness to maintain performance. SNUMAX has three key components: transformable origami wheels, a polymer-based variable stiffness manipulator, and an adaptive caging gripper. This paper describes the design of these components, and how they worked together to allow the robot to perform the contest’s navigation and manipulation tasks.

October 17, 2016 by admin 0 Comments

The effects of moisture and temperature on the mechanical properties of additive manufacturing components: fused deposition modeling

Authors
Eunseob Kim, Yong-Jun Shin, Sung-Hoon Ahn
Abstract
Purpose This paper aims to investigate the water absorption behaviors and mechanical properties, according to water absorption and temperature, of components fabricated by fused deposition modeling (FDM) and injection molding. The mechanical properties of FDM and injection molded parts were studied under several environmental conditions. Design/methodology/approach FDM components can be used as load-carrying elements under a range of moisture and temperature conditions. FDM parts show anisotropic mechanical properties according to build orientation. Components were fabricated from acrylonitrile-butadiene-styrene in three different orientations. The mechanical properties of parts fabricated by FDM were compared to injection molded components made from the same material. Water absorption tests were conducted in distilled water between 20 and 60°C to identify the maximum water absorption rate. Both moisture and temperature were considered as environmental variables in the tensile tests, which were conducted under various conditions to measure the effects on mechanical properties. Findings The water absorption behavior of FDM components obeyed Fickian diffusion theory, irrespective of the temperature. High temperatures accelerated the diffusion rate, although the maximum water absorption rate was not affected. The tensile strength of FDM parts under dry, room temperature conditions, was approximately 26-56 per cent that of injection molded parts, depending on build orientation. Increased temperature and water absorption had a more significant effect on FDM parts than injection molded components. The tensile strength was decreased by 67-71 per cent in hot, wet environments compared with dry, room temperature conditions. Originality/value The water absorption behavior of FDM components was investigated. The quantitative effects of temperature and moisture on tensile strength, modulus and strain were also measured. These results will contribute to the design of FDM parts for use under various environmental conditions.

May 21, 2016 by admin 0 Comments

Development of a polymer-based tendon-driven wearable robotic hand

Authors
Brian Byunghyun Kang, Haemin Lee, Hyunki In, Useok Jeong, Jinwon Chung, Kyu-Jin Cho
Abstract
This paper presents the development of a polymer-based tendon-driven wearable robotic hand, Exo-Glove Poly. Unlike the previously developed Exo-Glove, a fabric-based tendon-driven wearable robotic hand, Exo-Glove Poly was developed using silicone to allow for sanitization between users in multiple-user environments such as hospitals. Exo-Glove Poly was developed to use two motors, one for the thumb and the other for the index/middle finger, and an under-actuation mechanism to grasp various objects. In order to realize Exo-Glove Poly, design features and fabrication processes were developed to permit adjustment to different hand sizes, to protect users from injury, to enable ventilation, and to embed Teflon tubes for the wire paths. The mechanical properties of Exo-Glove Poly were verified with a healthy subject through a wrap grasp experiment using a mat-type pressure sensor and an under-actuation performance experiment with a specialized test set-up. Finally, performance of the Exo-Glove Poly for grasping various shapes of object was verified, including objects needing under-actuation.