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Precise Manufacturing and Performance Validation of Paper-Based Passive Microfluidic Micromixers
Mahdee Samae,Pawarit Ritmetee,Somyot Chirasatitsin,Sanja Kojić,Tijana Kojić,Jovana Jevremov,Goran Stojanović,Hani Al Salami 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.3
Micromixers are one of the most frequently used components in microfluidics. Passive micromixers are an emerging type with unique features in terms of reliability, robustness and efficiency. Hence, this study aimed to design, fabricate and test new multilayered passive micromixers consisting of three ad hoc layers, by means of a precise and cost-effective xurography manufacturing technique. The first and third layers are PVC foils, whereas the second layer is paper, incorporating microchannels of straight line or zig-zag configuration. Three different types of papers were analyzed as materials for the middle layer. Results demonstrated that immersing the papers into paraffin wax resulted in significantly improved physical characteristics, including solidification and intactness that reduced leakage of fluids into inside channels, thereby enhancing internal efficacy and delivery mechanisms. Subsequent assessments were carried out on mixing performance at various flow rates, pattern-related flow rates at various pressures and paper types, and results showed the impact of a zig-zag versus straight line configuration, demonstrating the importance of flow patterns on features of micromixers and their applications in microfluidic devices. Furthermore, image analysis was conducted to determine mixing efficiency of the proposed microfluidic micromixers.
Temperature Sensors Manufactured from Edible Materials Intended for Oral Cavity Operation
Goran M. Stojanović,Milan Radovanović,Sanja Kojić,Lazar Milić,Mitar Simić,Naturality Company,Raphael Georges Duval,Jelena Vukmirović,Bojan Petrović 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.1
Following the circular economy concept, all areas of science, including electronics, require individual approach. The green electronics approach implies processing natural based materials for development of electronic components even for single use, so that waste does not exist. This paper describes the production of thermistors from 3 different types of edible materials, their testing in laboratory conditions, as well as the application for measuring the temperature in the human oral cavity. To make the thermistor, three types of natural materials were used (carrageenan, polyvinyl alcohol and apple pomace-based). After fabrication, materials were poured into molds. Aluminium foil contacts were placed so that the electrical characterization of the materials could be performed. Several parameters were measured: resistance (R), impedance (Z) and the phase angle (θ) as a function of frequency. In order to determine whether the thermistors have a positive or negative temperature coefficient and to determine their sensitivity, measurements were conducted at three different temperatures: 25 ℃ (room temperature), 37 ℃ (human body temperature), and 50 ℃. The thermistors demonstrated negative temperature coefficient behaviour. Additionally, it was demonstrated that the apple pomace-based thermistor can successfully measure healthy volunteer's temperature.
Development of a Test Method for Walking Trolleys with an Assist Function
Koji Matsumoto,Yoichi Asano,Hiroyuki Jinbo 제어로봇시스템학회 2019 제어로봇시스템학회 국제학술대회 논문집 Vol.2019 No.10
Walking trolleys that are currently being manufactured have a function that prevents downslope movement when the user crosses a slope. In this study, we have developed a test method to evaluate this function. First, we measured the handle-operating force exerted by elderly persons when crossing a slope by carrying out an experiment with 17 elderly participants. Analysis of the results indicated that the handle-operating force was 28 N. Based on these results, we developed a test method and a test equipment. Furthermore, we used the test equipment to conduct experiments on walking trolleys with and without activating the assist function to validate the test method. It was found that the proposed test can be performed with sufficient accuracy.