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10 results on '"Lee, Sunkey"'

4. 3D Fabrication of Fully Iron Magnetic Microrobots

Author

Alcântara, Carlos C.J., Kim, Sangwon, Lee, Sunkey, Jang, Bumjin, Thakolkaran, Prakash, Kim, Jin-Young, Choi, Hongsoo, Nelson, Bradley J., and Pané, Salvador

Subjects
direct laser writing, iron electrodeposition, magnetic microrobots, template‐assisted deposition, upstream motion
Abstract

Small, 15 (16), ISSN:1613-6810, ISSN:1613-6829

Published
2019

9. Autogenous shrinkage of concrete containing granulated blast-furnace slag

Author

Kwang-Myong Lee, Lee Sunkey, Hyunyeul Lee, and Gyu-Yong Kim

Subjects
Water–cement ratio, Materials science, Shrinkage strain, Slag, Building and Construction, Stress (mechanics), Ground granulated blast-furnace slag, visual_art, visual_art.visual_art_medium, General Materials Science, Cementitious, Composite material, Material properties, Shrinkage
Abstract

This paper presents the experimental results and prediction model for the autogenous shrinkage of concrete made with various water-to-cementitious materials ratios ( w / cm) ranging from 0.27 to 0.42 and granulated blast-furnace slag (BFS) in the range of 0% to 50% by mass of the total cementitious materials. Test results showed that BFS concrete exhibited greater autogenous shrinkage than ordinary concrete with no BFS with the same w / cm, and that the higher the BFS content, the greater the autogenous shrinkage. At the same content of BFS, the increasing rate of autogenous shrinkage is affected by the w / cm; the lower the w / cm, the smaller the increasing rate of autogenous shrinkage. Based on the test results, a prediction model for autogenous shrinkage was proposed. In particular, an effective autogenous shrinkage that is a realistic shrinkage strain responsible for stress development was introduced in the model. It was determined by taking into account the characteristics of ultrasonic pulse velocity evolution in concrete. This prediction method for autogenous shrinkage may be effectively used to estimate the stress induced by autogenous shrinkage.

Published
2006
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10. 3D Fabrication of Fully Iron Magnetic Microrobots.

Author

Alcântara CCJ, Kim S, Lee S, Jang B, Thakolkaran P, Kim JY, Choi H, Nelson BJ, and Pané S

Subjects
Biocompatible Materials, Electrochemistry, Electroplating, HCT116 Cells, Humans, Hydrogen chemistry, Magnets, Microfluidics, Robotics methods, Surface Properties, Iron chemistry, Magnetic Fields, Microtechnology methods, Printing, Three-Dimensional instrumentation, Robotics instrumentation
Abstract

Biocompatibility and high responsiveness to magnetic fields are fundamental requisites to translate magnetic small-scale robots into clinical applications. The magnetic element iron exhibits the highest saturation magnetization and magnetic susceptibility while exhibiting excellent biocompatibility characteristics. Here, a process to reliably fabricate iron microrobots by means of template-assisted electrodeposition in 3D-printed micromolds is presented. The 3D molds are fabricated using a modified two-photon absorption configuration, which overcomes previous limitations such as the use of transparent substrates, low writing speeds, and limited depth of field. By optimizing the geometrical parameters of the 3D molds, metallic structures with complex features can be fabricated. Fe microrollers and microswimmers are realized that demonstrate motion at ≈20 body lengths per second, perform 3D motion in viscous environments, and overcome higher flow velocities than those of "conventional 3D printed helical microswimmers." The cytotoxicity of these microrobots is assessed by culturing them with human colorectal cancer (HCT116) cells for four days, demonstrating their good biocompatibility characteristics. Finally, preliminary results regarding the degradation of iron structures in simulated gastric acid liquid are provided., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2019
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