In this paper, a microfluidic co-culture system comprising an embedded polydimethylsiloxane (PDMS) microstencil was fabricated. The fabricated co-culture system has two micro-channels separated with a PDMS microstencil membrane. Master molds for microchannels and stencil membranes were fabricated by photolithography, then used for casting of PDMS devices. The stencil membrane was 10 thick, with holes 10-μm large in diameter. The fabricated system co-cultured two types of cells (HepG2, NIH-3T3 Cells) successfully for seven days. The viability and stability of the cells were verified through LIVE/DEAD® staining and analysis. Additionally, albumin secretion of HepG2 cells was measured for seven days, using an HSA ELISA kit. The measured data were analyzed, to compare the activity of HepG2 cells. Results confirmed that cells can be co-cultured in the fabricated microfluidic system.
This paper proposes a practical method, for evaluating 3-D positioning of outdoor mobile robots using the Unscented Kalman Filter (UKF). The UKF method does not require the linearization process unlike conventional EKF localization, so it can minimize effects of errors caused by linearization of non-linear models for position estimation. Also, this method does not require Jacobian calculations difficult to calculate in the actual implementation. The 3-D position of the robot is predicted using an encoder and tilt sensor, and the optimal position is estimated by fusing these predicted positions with the GPS and digital compass information. Experimental results revealed the proposed method is stable for localization of the 3D position regardless of initial error size, and observation period.
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Research on Parameter Compensation Method and Control Strategy of Mobile Robot Dynamics Model Based on Digital Twin Renjun Li, Xiaoyu Shang, Yang Wang, Chunbai Liu, Linsen Song, Yiwen Zhang, Lidong Gu, Xinming Zhang Sensors.2024; 24(24): 8101. CrossRef
A Study on Improving the Sensitivity of High-Precision Real-Time Location Receive based on UWB Radar Communication for Precise Landing of a Drone Station Sung-Ho Hong, Jae-Youl Lee, Dong Ho Shin, Jehun Hahm, Kap-Ho Seo, Jin-Ho Suh Journal of the Korean Society for Precision Engineering.2022; 39(5): 323. CrossRef
Sound waves propagate in a manner in which energy is transmitted by adjacent molecules in the medium. These adjacent molecules exhibit inherent sound wave characteristics, such as height and wavelength, depending on the sound frequency. The Helmholtz resonator, one of the well-known acoustic elements, comprises a neck and a cavity, and features a resonance at a specific frequency related to structural dimensions. The acoustic characteristics of the Helmholtz resonator can be explained by a lumped spring-mass system in mechanical engineering; the resonant frequency can be calculated with the same analysis. The Helmholtz resonator is widely used as an acoustic filter as it can re-radiate sound waves with the opposite phase and significantly attenuate the original sound wave in the resonance frequency range. In this study, we fabricated a Helmholtz resonator-inspired film-type acoustic absorber (FAA), comprising a microscale resonator array made with polydimethylsiloxane (PDMS). Through acoustic attenuation experiments, the FAA revealed that the novel attenuation values reached up to 36.3 dB mm-1. Additionally, a continuous fabrication of the FAA was achieved via a custom-built roll-type equipment.
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Fabrication and Performance Evaluation of the Helmholtz Resonator Inspired Acoustic Absorber Using Various Materials Sung Ho Lee, Bong Su Kang, Gyu Man Kim, Yong Rae Roh, Moon Kyu Kwak Micromachines.2020; 11(11): 983. CrossRef
This paper proposes a 3D localization method for an outdoor mobile robot. This method assesses the 3D position including the altitude information, which is impossible in the existing 2D localization method. In this method, the 3D position of the robot is predicted using an encoder and an inclination sensor. The predicted position is fused with the position information obtained from the DGPS and the digital compass using extended kalman filter to evaluate the 3D position of the robot. The experimental results showed that the proposed method can effectively evaluate the 3D position of the robot in a sloping environment. Moreover, this method was found to be more effective than the conventional 2D localization method even in the evaluation of the plane position where altitude information is unnecessary.
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Research on Parameter Compensation Method and Control Strategy of Mobile Robot Dynamics Model Based on Digital Twin Renjun Li, Xiaoyu Shang, Yang Wang, Chunbai Liu, Linsen Song, Yiwen Zhang, Lidong Gu, Xinming Zhang Sensors.2024; 24(24): 8101. CrossRef
Unscented Kalman Filter Based 3D Localization of Outdoor Mobile Robots Woo Seok Lee, Min Ho Choi, Jong Hwan Lim Journal of the Korean Society for Precision Engineering.2020; 37(5): 331. CrossRef
We introduce technological development of stencil lithography, for new micro and nano fabricated method as a patterning technique. Stencil lithography has advantages of photoresistless, reusable patterning technique, and large area micro and nano patterning. The principle of stencil lithography is as follows: Materials are deposited through perforated holes on the membrane surface, of stencil in micro and nanoscale. In this paper, the fabrication method and application of three types of stencils, are reviewed according to the material. Solid-state stencils based on silicon, are fabricated by micro-fabrication processing of photolithography and etching. Metal stencils are fabricated by metal etching, electroforming, and laser machining. Polymer stencils are fabricated by molding and casting of polymers, such as PDMS, Hydrogel and Photocrosslinkable polymer, etc. Stencils fabricated from a variety of ways may be applied to nanopatterns, nano-wire patterning, and metal electrode fabrication, and used in metal deposition or etching masks and non-planar surface metal patterning techniques. Stencil lithography is applied in various areas of flexible displays, bio-devices, wearable sensors, etc.
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Single-cell patterning: a new frontier in bioengineering R. Gayathri, S. Kar, M. Nagai, F.-G. Tseng, P.S. Mahapatra, T.S. Santra Materials Today Chemistry.2022; 26: 101021. CrossRef
This paper presents results for effects of the liquid surface tension on the ejected droplet volume using a pneumatic printing system. The low surface tension of the solution causes the liquid wetting around the nozzle, and then the wetted nozzle also inhibits stable formation of droplets. First, we confirmed the maximum inlet pressure (i.e., balanced with capillary force on the outlet channel) corresponding to varied surface tensions of the solutions, prepared by controlling the concentration of a surfactant. The ejected droplet volumes with the surfactant concentrations was varied within approximately 7% at each maximum inlet pressure, and the volume variation decreased to a fifth as compared with a high surface tension liquid.
In this study, we propose a fabrication method of three-dimensional complex shape polydimethylsiloxane microstencils. Three-dimensional complex shape polydimethylsiloxane (PDMS) microstencils were fabricated by an air-knife system and PDMS casting form preparing master mold by photolithography, diffuser lithography and polyurethane acrylate (PUA) replication. PDMS microstencils shape was a production of the hemispherical and quadrangular pyramid. When the prepolymer of PDMS was spin-coated onto the three-dimensional complex shape master mold, a thin layer of prepolymer remained on top of the master"s structure and consequently prevented formation of perforated patterns. This residual layer was easily removed by the air-knife. The air-knife system was controlled by the flow rate of N2 gas and conveying speed of the master mold. Results revealed the fabricated three-dimensional complex shape PDMS microstencils, could be useful for application of three-dimensional cell culture device.
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Review on Microstencil Lithography Technologies Jin Ho Choi, Hye Jin Choi, Gyu Man Kim Journal of the Korean Society for Precision Engineering.2018; 35(11): 1043. CrossRef
In this study, drop-on-demand system using piezo-elecrtric inkjet printers was employed for preparation of collagen microspheres, and its application was made to the HepG2 cell-laden microsphere preparation. The collagen microspheres were injected into beaker filled with mineral oil and incubated in a water bath at 37℃ for 45 minutes to induce gelation of the collagen microsphere. The size of collagen microsphere was 100μm in diameter and 80μm in height showing spherical shape. HepG2 cells were encapsulated in the collagen microsphere. The cellladen microspheres were inspected by the microscopic images. The encapsulation of cells may be beneficial for applications ranging from tissue engineering to cell-based diagnostic assays.
In this presentation, we propose a fabrication method of PDMS stencil to apply into a localized culture of NIH/3T3 cells. PDMS stencil was fabricated by nitrogen gas blowing and soft lithography from preparing SU-8 master mold by photolithography. PDMS stencil pattern was production of the circle size 20 to 500 μm. In the culture test of PDMS stencil, a stencil was placed on a glass disk. The NIH/3T3 cells were successfully cultured into micropatterns by using the PDMS stencil. The results showed that cells could be cultured into micropatterns with precisely controlled manner at any shapes and specific size for bioscience study and bioengineering applications.
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