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Biocompatible micro, soft bellow actuator rapidly manufactured using 3D-printed soluble mold
Jung, Woojun,Kang, Yoon,Han, Seungoh,Hwang, Yongha IOP 2019 Journal of micromechanics and microengineering Vol.29 No.12
<P>A micro, soft bellow actuator, which is fabricated using a biocompatible material (polydimethylsiloxane (PDMS)) and operates in a pneumatic manner that is harmless to the living body, has been experimentally validated using 3D-printed soluble molds and supports. Typical planar microfabrication techniques for flexible pneumatic actuators with complex geometries generally have inherent design limitations owing to the manner in which 2D thin films are stacked and require multiple lithographic and alignment steps. In this study, micro bellow actuators with 3D structures that cannot be fabricated using the existing softlithography techniques were designed by simulating the mechanical behavior of the actuator based on the nonlinear elastic properties of PDMS. The subsequently designed 3D-printed soluble-mold technique was used to fabricate the bellow actuators with a 10 <I>µ</I>m resolution, while taking into consideration the printing quality, which depends on the printing direction and layer thickness of the 3D printer. On evaluating the operating performance, the micro bellow actuator showed a displacement of 1540 <I>µ</I>m at the applied pneumatic pressure of 60 kPa and can apply a force of 0.14 N. Even after 10 000 repetitive operations, the change in the operating characteristic was less than 0.44%. It was also demonstrated that fast prototyping of actuators within 48 h is possible without any process revision, even with variable design changes or other soft polymer materials. The reported fabrication technique is a superior approach for fabricating 3D, sealed, soft pneumatic actuators for micro, soft robot applications.</P>
Gyu Seop Hwang,Hongje Jang,Yang-Rae Kim,Woojun Shin,Gyeonghye Yim,Jae Hyuk Choi,Young-Kwan Kim 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.11
Rh nanoparticles (RhNPs) have attracted significant attention due to their superiorelectrocatalytic activity in several energy conversion reactions. However,studies relating their morphology and performance are rare. In this study, threetypes of RhNPs, i.e., nanoshells, nanoframes, and porous nanoplates, were synthesizedvia inverse-directional galvanic replacement. The relationship betweenthe performance of the RhNPs at catalyzing the oxygen reduction reaction(ORR) and their morphology was investigated using cyclic voltammetry, linearsweep voltammetry, the Tafel slope, and electrochemical impedance spectroscopy. X-ray photoelectron spectroscopy and X-ray diffraction data revealed thatthe RhNPs contained different Rh/Ag ratios. All the RhNPs exhibited long-termstability under acidic conditions. In particular, nanoshell-structured RhNPsexhibited superior ORR activity as determined from the slope of the Tafel plot,the number of electrons, and the onset potential compared to a commercialRh electrocatalyst and other RhNPs. Evidently, controlling the morphology andcomposition of RhNPs greatly facilitates efficient electrocatalysis.
Enabling technologies for AI empowered 6G massive radio access networks
Md. Shahjalal,Woojun Kim,Waqas Khalid,Seokjae Moon,Murad Khan,ShuZhi Liu,Suhyeon Lim,Eunjin Kim,Deok-Won Yun,Joohyun Lee,Won-Cheol Lee,Seung-Hoon Hwang,Dongkyun Kim,Jang-Won Lee,Heejung Yu,Youngchul S 한국통신학회 2023 ICT Express Vol.9 No.3
Predictably, the upcoming six generation (6G) networks demand ultra-massive interconnectivity comprising densely congested sustainable small-to-tiny networks. The conventional radio access network (RAN) will be redesigned to provide the necessary intelligence in all areas to meet required network flexibility, full coverage, and massive access. In this respect, this paper focuses on intelligent massive RAN (mRAN) architecture and key technologies fulfilling the requirements. Particularly, we investigate potential AI algorithms for network and resource management issues in 6G mRAN. Furthermore, we summarize the research issues in edge technologies and physical layer intelligence on 6G network architecture.
Droplet generation with integrated 3D pneumatic actuator for orifice control
Chanju Lee,Yongseong Cho,Woojun Jung,Jumi Lee,Yongha Hwang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.1
A droplet generator with an embedded 3D balloon actuator around a flowfocusing junction is realized to adjust the size of the droplets as required with only one element. The 3D actuator encircling the orifice causes a geometric deformation due to pneumatic pressure, which controls the orifice and thus the sizes of the droplets. The orifice and actuator are designed to have triangular cross-sections with the largest possible reduction in hydraulic diameters under the same pneumatic pressure. We empirically demonstrated that, compared with typical fixed orifice structures, droplet generators with variable orifices reduce the droplet size without changing the flow rate and can even be adjusted to a wider range of 259.3 %. The devices were fabricated by the 3D-printed soluble mold technique to achieve a fully 3D structure within a single body of polydimethylsiloxane that is unattainable by conventional standard microfabrications as well as a non-bonding structure without any leakage.