An Alignment-Free Sensing Module for Noninvasive Radial Artery Blood Pressure Measurement

Sensor–artery alignment has always been a significant problem in arterial tonometry devices and prevents their application to wearable continuous blood pressure (BP) monitoring. Traditional solutions are to use a complex servo system to search for the best measurement position or to use an inefficient pressure sensor array. In this study, a novel solid–liquid mixture pressure sensing module is proposed. A flexible film with unique liquid-filled structures greatly reduces the pulse measurement error caused by sensor misplacement. The ideal measuring location was defined as −2.5 to 2.5 mm from the center of the module and the pressure variation was within 5.4%, which is available in the real application. Even at a distance of ±4 mm from the module center, the pressure decays by 23.7%, and its dynamic waveform is maintained. In addition, the sensing module is also endowed with the capability of measuring the pulse wave transmit time as a complementary method for BP measuring. The capability of the developed alignment-free sensing module in BP measurement was been validated. Twenty subjects were selected for the BP measurement experiment, which followed IEEE standards. The experimental results showed that the mean error of SBP is −4.26 mmHg with a standard deviation of 7.0 mmHg, and the mean error of DBP is 2.98 mmHg with a standard deviation of 5.07 mmHg. The device is expected to provide a new solution for wearable continuous BP monitoring.

Material Modeling of PMMA Film for Hot Embossing Process

This study provides an analysis of the hot embossing process with poly methyl methacrylate (PMMA) film. The hot embossing process engraves a fine pattern on a flexible film using a stamp, applied heat and pressure. As the quality of the embossing pattern varies according to various process variables, the mechanism of making the embossed shape is complicated and difficult to analyze. Therefore, analysis takes much time and cost because it usually has to perform a lot of experiments to find an appropriate process condition. In this paper, the hot embossing process was analyzed using a computational analysis method to quickly find the optimal process. To do this, we analyzed the embossing phenomenon using the finite element method (FEM) and arbitrary Lagrangian–Eulerian (ALE) re-mesh technique. For this purpose, we developed a constitutive model considering the strain, strain rate, temperature-dependent stress and softening of the flexible film. Work hardening, strain softening, and temperature-softening behavior of PMMA materials were well described by the proposed method. The developed constitutive model were applied in the embossing analysis via user-subroutine. This proposed method allowed a precise analysis of the phenomenon of film change during the hot embossing process.

Initial Properties Identification of Refined- and Semi Refined-Carrageenans as Raw Materials for Biodegradable Plastic Production

Powdered refined- and semi-refined carrageenans (RC and SRC) have been characterized as alternative raw materials for industrial bioplastic production. Several basic parameters, i.e., the melting temperature, crystallinity, chemical structure (FTIR), and tensile properties, were observed. The melting temperature of RC was slightly higher than that of SRC, i.e., 176 °C and 172 °C, respectively. These temperatures were corresponded to their crystallinity degree (performed by X-ray diffraction). Nonetheless, the SRC demonstrated an overall higher thermal stability during heating. RC produced a clear transparent film. Meanwhile, SRC was yellowish and less transparent. The overall mechanical properties showed that RC produced more flexible film than SRC. However, both materials showed relatively equal tensile strength. In general, RC and SRC could be potentially used for biodegradable film production with different applications. RC was suitable for a flexible and clear plastic film, whereas SRC was suitable for rigid plastic film applications.