Improvement of the Usability of Online Mentoring Website

The purpose of this study is to improve the usability of the current online mentoring website by deriving what should be improved through assessment and reflecting it to system improvement. The related data such as search log and Think Aloud were collected from user groups (9 users in total), and usability was tested according to the predefined test procedures. The collected data were analyzed, using quantitative methods. In terms of search log, the related items including effectiveness, efficiency, satisfaction and error were quantified according to usability testing standards. Then, descriptive statistics was performed. According to usability comparison before and after system improvement, it has mostly improved such as improved effectiveness (increase by 15 points), better efficiency (reduction by 41 seconds), increase in satisfaction (by 8 points) and decrease in error frequency (decrease by 1.2 times). Usability testing should be viewed as a process, not outcome itself. Therefore, it could be used during system prototype in addition to the current system and useful in system improvement

Design of Security Platform via Holographic Metasurface with Oblique Helicoidal Liquid Crystals

Metasurfaces (MSs) with sub-wavelength scale of nanostructures have an ability to respond to the properties of incident light (e.g., wavelength, polarization, incident angle) and provide a corresponding programmed optical signal that are predetermined by configuration of nanostructures. Because the configurations of light and nanostructures have the infinite degrees of freedom, therefore, the metasurfaces have been considered as promising security platform that does not allow computational decryption . Here, we propose the simple and versatile design of high security platform via wavelength responsive MS integrated with the layer of oblique helicoidal liquid crystals (LCs). Specifically, we design MS to display holographic images only when target wavelengths of light are exposed. The integrated LC layers are programmed to reflect the target wavelengths under the specific electric field and temperature. Consequently, we demonstrate our security platform to show the encrypted holographic image only when the programmed electric field and temperature are applied. This work was supported by the NRF (2021R1A4A1030944, 2021R1A2C2095010, 2022M3C1A3081312).2

Controlled pattering of surface micro-droplets via micellization of Polymeric Amphiphiles in liquid crystalline fluids

In this work, we report a simple and versatile approach to pattern microdroplets of liquid crystals (LCs) encapsulated by polymeric amphiphiles on substrates. When the thermal trigger is introduced into a LC layer confined between two bounding plates coated with Poly (octadecyl methacrylate) (PODMA), we observed PODMA to diffuse into the LCs and form micro-sized droplets onto the substrates upon cooling. The size and density of droplets are precisely controllable by the tail length of PODMA, heating temperature, and rate of temperature change. We demonstrate the formation of surface droplets to be associated with the micellization of PODMA in LCs. The thermal trigger (increase in temperature) facilitates the desorption of coated PODMAs from substrates and the diffusion of them into LCs. The subsequent decrease in temperature reduces the critical micelle concentration of PODMA, thus resulting in the formation of birefringent quasi-2D hemisphere droplet. In addition, we found the internal configuration of LCs and the morphology of droplets to be controllable via anchoring energy, roughness, and waviness of bounding plates. This work was supported by the NRF (2021R1A4A1030944 and NRF-2021R1A2C2095010).2

Array of One-dimensional Atomic Crystals for Emerging Electronic Platform

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