In this work, Mg1-xZnxO thin films were deposited on glass substrates by the pneumatic spray technique at 450°C using a 0.15 M precursor solution of magnesium acetate and zinc acetate. The effect of Zn content (x = 0, 0.3, 0.5, and 0.7%) on the structural, morphological, optical, and electrical properties of the films was examined. XRD analysis showed that all films adopted a cubic MgO structure with diffraction peaks from the (111), (200), and (220) planes, and the crystallite size grew from 8.12 to 12.49 nm as the Zn content increased. SEM images indicated that moderate Zn incorporation improved film homogeneity, whereas higher Zn contents promoted agglomeration and surface roughening. The films transmitted well in the visible region, and the optical band gap widened from 3.56 to 3.93 eV at x = 0.3. The Urbach energy also rose with Zn content, reaching a maximum of 0.695 eV at x = 0.7, which indicates greater structural disorder. FTIR spectra confirmed that Zn incorporation modifies the chemical bonding network. The sheet resistance increased markedly with Zn content, demonstrating the strong influence of Zn doping on the optical and electrical properties of MgO thin films.
The pneumatic vibration isolator is economical, has no risk of contamination, and attains high vibration isolation performance by lowering the natural frequency. Pressure feedback control is used to improve the response speed of the pneumatic vibration isolator and keep the internal pressure of the pneumatic actuator constant. In this paper, the vibration isolator was actively controlled by estimating the internal pressure of the pneumatic actuator with the displacement signal. A pneumatic actuator was modeled and its dynamic characteristics were identified through frequency response measurements. A pressure observer based on relative displacement was designed, and the observer control gain was adjusted with nominal model and experiments. Pressure estimation performance and active vibration suppression performance using a pressure observer were verified through experiments. The pressure of the pneumatic actuator was estimated by the observer, and measurement noise was eliminated effectively. In addition, vibration isolation performances of direct and estimated pressure feedback showed no difference, verifying the effectiveness of the pressure observer.
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Development of an Ultra-precision Air-bearing Stage Integrated with Real-time Motion Error Measurement and Compensation Functions Eun Young Ko, Hoon Hee Lee, Kwang Il Lee, Seung Han Yang Journal of the Korean Society for Precision Engineering.2026; 43(2): 167. CrossRef
In this work, precise gas pressure control based on a closed pneumatic circuit was achieved with a mechanically driven gas pressure controller (MDGPC), consisting of a variable-volume bellows chamber and linear actuator. The linear actuator was employed to change an axial dimension of the bellows chamber with the proportional (P) and proportional-integral (PI) controls for fast, stable, and precise pressure control of the gas inside the bellows chamber. The pressure control stability and resolution of the MDGPC were approximately 1.5 Pa and 10 Pa for the P control and 1 Pa and 5 Pa for the PI control, respectively. Despite the more stable and precise control characteristics of the PI control method, overshoots and undershoots observed during the set-point pressure changes and recoveries from pressure disturbances rendered it unsuitable for the MDGPC control method. In contrast, the MDGPC operated under the P control did not show any significant overshoots or undershoots when the set-point pressure abruptly changed or when the MDGPC was exposed to pressure disturbances. Therefore, it was concluded that a fast, precise, and stable gas pressure control in a closed manner was attainable with the MDGPC under the P control.
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Pneumatic temperature control characteristics of a variable-load heat source with a pressure-controlled loop heat pipe Bomi Nam, Wukchul Joung International Communications in Heat and Mass Transfer.2025; 166: 109219. CrossRef
Temperature uniformity of a hybrid pressure-controlled loop heat pipe with a heat pipe liner Bomi Nam, Cheongyong Park, Wukchul Joung International Communications in Heat and Mass Transfer.2024; 156: 107656. CrossRef
Progresses in Pneumatic Temperature Control Technique for Ultra-Precise Control and Measurement of Thermal Environment Bomi Nam, Wukchul Joung Journal of the Korean Society for Precision Engineering.2024; 41(10): 759. CrossRef
The soft robotics field, known to have actuators and systems with a simple manufacturing process, being lightweight and safe to interact with humans, is in constant expansion. Present actuators have excessive unwanted deformations, which greatly affects the system"s performance by enlarging the external dimensions of the soft robot, reducing its efficiency, and causing unexpected or harmful contact with its surrounding environment. Thus, this work presented an actuator with a spring-like structure within a pneumatic chamber able to contract based on its innate design and lengthen when hyper-atmospheric pressures are applied, resulting in tension and torsion. A tensile testing machine and a force-torque sensor coupled with the actuator were used to evaluate its performance for different initial lengths, pressure inputs, and number of coils. At 30 kPa, a torque of up to 5 Nm was generated, have a maximum torsional angle of 41 degrees, and expanded 700% of its original length. Results have shown that the studied pneumatic-based expanding torsional soft spring actuator can stably lengthen under pneumatic pressure, resulting in sufficient force and considerable torque, and could be considered in future applications.
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.
We present a multi-sample array device based on a pneumatic system. Solenoid valves were used to control a micro valve in a pneumatic system. The use of a compressor together with a vacuum pump ensured that one outlet could supply both compression and vacuum pressure. The multi-sample array device was fabricated using conventional photolithography and PDMS casting. The device was composed of a multiplexer, sample array, and rinsing. The multiplexer could control four sample solutions injecting into the sample array chamber. Sample solution not arrayed was removed by DI-water from the rinsing inlet. To prevent trapping of microbubbles in the channel during injection of sample solution into the device, surfactant was added in PDMS solution to serve as a hydrophilic surface treatment. As a result, the device could be used as a sample array for 64 cases, using four samples and three columns of three chambers.
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Shape Optimization of Pneumatic Angle Valve Using Structural Analysis In-Soo Son Journal of Power System Engineering.2020; 24(5): 48. CrossRef
Non-Contact Intraocular Pressure Measurement Method using Relation between Deformed Cornea and Reflected Pneumatic Pressure Hyung Jin Kim, Young Ho Seo, Byeong Hee Kim International Journal of Precision Engineering and Manufacturing.2018; 19(5): 737. CrossRef
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