Due to their structural properties, nanopatterns are actively used in various fields. In the semiconductor industry, the importance of analyzing the uniformity of nanopatterns is becoming increasingly important. New analysis methods are needed. The elliptical Fourier descriptor (EFD) method can quantify the shape information into frequency components by Fourier transforming contours. In this study, shape analysis of nanopatterns was performed using EFD. Nanopatterns with a period of about 400 nm were formed using laser interference lithography. EFD coefficients were then compared. Results of the analysis showed that the variation between coefficients of poorly shaped patterns was larger than that of normal patterns, confirming the possibility of quantitative comparison. However, further research is needed to establish a clear correlation between coefficient changes and quality changes. In the absence of a standard for geometrical changes in nanopatterns, it is expected that EFD can be applied as a methodology to provide new quantitative indicator.

We present a xenon arc source-based illumination system designed to achieve high spatial uniformity and efficient light collection across a wide spectral range. The proposed optical system comprised an ellipsoid reflector, diffuser, motorized iris, and collimation lens to optimize beam homogenization. Non-sequential ray-tracing simulations were performed to evaluate angular irradiation distributions of various diffusers and the overall beam profile uniformity. The system was experimentally implemented using a fused silica holographic diffuser optimized for high-power operation, with a motorized iris enabling precise control of light intensity. The resulting beam profile exhibited a well-defined flat-top shape, with a beam uniformity of approximately 95% evaluated according to the ISO 13694 standard. The developed illumination system demonstrated its ability to produce highly uniform illumination, suitable for various optical applications including spectroscopy, precision measurement, and optical imaging.

In this paper, we introduce a new pneumatic temperature control technique and its application to precision thermometry. The method controls temperature by adjusting gas pressure through the unique thermohydraulic linkage of the pressure-controlled loop heat pipe (PCLHP). Due to this temperature-pressure linkage, the PCLHP-based pneumatic temperature control achieves exceptional control speed, stability, and precision. To fully understand this method, we systematically investigated the effects of various influencing parameters, such as heat load, sink temperature, and rate of pressure change, on the stability of temperature control. In addition, we successfully achieved closed-type pneumatic temperature control using a mechanically-driven gas pressure controller. We also developed a hybrid PCLHP that incorporates a heat pipe liner into the isothermal region to further improve the temperature uniformity of the pneumatically-controlled temperature field. With this technique, we significantly improved the accuracy of the fixed point of the International Temperature Scale of 1990 by using inside nucleation of the freezing temperature of tin and determining the liquidus temperature of tin. In this paper, we summarize the results of these diverse efforts in characterizing the pneumatic temperature control technique, along with theoretical analyses.

Slot-die coating is a method of coating a wide layer of thin film on a substrate. It has the advantages of large-area coating with high reproducibility and uniform thickness. For this reason, it has been widely applied in various industrial manufacturing fields. To secure higher coating uniformity under various coating conditions, estimating and controlling the flow rate of the coating solution discharged to the substrate is crucial. In this study, a practical gravimetric flow rate measurement method for slot-die coating uniformity evaluation has been introduced. The gravimetric method is a technique for accurately and quickly estimating the flow rate through the mass change over time using a precision weighing balance. We analyzed the measurement principle and errors caused by fluid mechanics such as hydrodynamic force or capillary force. The dynamic properties based on fluid viscosity were also evaluated for flow rates from 5 to 50 μL/s. The repeatability of the fabricated measurement system was ~1.5 μL/s. Finally, it was confirmed that the settling time for high-viscosity fluid could be advanced by 56.4% through multi-step feedforward control.

In this work, recent advances in temperature control techniques and the resulting contemporary progress in precision thermometry are addressed together with a broad review of traditional temperature control methods. Particular emphases are placed on clarification of the nature of temperature control and its classification, and the relevant technical issues are addressed based on this clarification and classification. Being a thermodynamic quantity having the same dimension as energy, temperature of an object is traditionally controlled by means of the changing rate of energy (Heat) transfer; however, this approach has led to a slow, less stable, and uneven temperature field due to inherent limits caused by finite properties of materials. To overcome this problem, thermodynamic characteristics of two-phase heat transfer devices, such as heat pipes and loop heat pipes, have been extensively employed where high-speed nature of fluid flow was exploited to realize a uniform temperature field, and unique thermodynamic linkage between saturation temperature and pressure was successfully applied to attain a fast, stable, and predictable temperature control of a finite-sized isothermal space. Representative examples and applications are provided in the context of unique features of the introduced contemporary temperature control techniques, which caused significant scientific strides in the related fields.

Three-dimensional (3-D) printing, with its capability for producing arbitrary shapes, has shown great potential for usage in patient-specific tissue engineering. However, if artificial tissues are fabricated directly through typical 3-D printing processes, the mechanical properties, particularly for softness or flexibility, significantly differ from those of natural tissues, resulting in inappropriate side effects during surgeries using vascular grafts. However, this can be overcome through the indirect 3-D printing of templates created with a thin-film formation process, such as dip coating. Dip coating is performed in two steps, including dipping/withdrawing a target base template from a polymer solution, and then drying the solvent into a solid thin film on the template. However, it is difficult to form a uniform layer on the arbitrary template because the gravitational flow of the coated solution disturbs the uniformity of the template as the solvent is drying. Therefore, we minimized the flow around the template after dip coating by rapidly removing the solvent removal by dipping the solution-coated template into ethanol. This reduced the solvent removal time and increased the viscosity of the coated solution, thereby alleviating the gravitational flow of the coated solution, and allowing us to successfully fabricate flexible vascular grafts.