This study introduces a measurement technique for simultaneous phase-separated velocity in two-phase bubbly flow. The non-invasive technique, based on an Ultrasonic Velocity Profiler (UVP), is used in order to obtain an instantaneous, separate velocity profile for both liquid and bubble. The aim of this paper is to measure each phase velocity at the same time and position it using only a single resonant frequency. To achieve this aim, extended signal processing of the Short-Time Fourier Transform (STFT) is proposed, combining with amplitude classification to analyze Doppler signal influenced from the bubbly flow. The use of developed algorithms allows the instantaneous separation of liquid and bubble velocity profiles. In this work, the developed technique is used to measure the velocity profile of bubbly flow in the vertical pipe, demonstrating the classification of liquid and bubble velocity. To confirm the accuracy of each velocity profile phase, the Particle Image Velocimetry (PIV) method is used for comparison. The results clarify that the proposed method is in good agreement with the PIV measurement. Finally, the effect of void fraction against velocity measurement of both phases was demonstrated.

As per sequential studies on new types of soft rubber for the artificial skin of robots, smart sensors, etc., we have proposed and investigated hybrid skin (H-Skin) and haptic sensors by using magnetic compound fluid (MCF), compounding natural rubber latex (NR-latex), and applying electric and magnetic fields. Through electrolytic polymerization, the MCF rubber is solidified. The MCF rubber has hybrid sensing functions and photovoltaic effects, and electric charge as battery. In case of the production of soft rubber sensors, however, the problem of adhesion between metal electrodes and rubber is very important. In the present study, we propose a novel adhesive technique for bonding the metal electrodes and MCF rubber by using metallic or non-metallic hydrous oxide, which is a metal complex, via electrolytic polymerization. The anionic radical hydrate reacts with the isoprene molecules of NR-latex or chloroprene rubber latex (CR-latex) such that they are cross-linked and the MCF rubber with the hydrate is solidified, which can be represented via a chemical reaction equation. By means of this adhesive technique, we presented five cases of sensors fabricated using metal electrodes and rubbers. This technique is applicable for novel cohesion between rubber and metal.

Sensors are essential in the haptic technology of soft robotics, which includes the technology of humanoids. Haptic sensors can be simulated by the mimetic organ of perceptual cells in the human body. However, there has been little research on the morphological fabrication of cutaneous receptors embedded in a human skin tissue utilizing artificial materials. In the present study, we fabricated artificial, cell-like cutaneous receptors embedded in skin tissue mimicking human skin structure by utilizing rubber. We addressed the fabrication of five cutaneous receptors (free nerve endings, Krause and bulbs, Meissner corpuscles, Pacinian corpuscles and Ruffini endings). In addition, we investigated the effectiveness of the fabricated tissue for mechanical and thermal sensing. At first, in the production of integrated artificial skin tissue, we proposed a novel magnetic, responsive, intelligent, hybrid fluid (HF), which is suitable for developing the hybrid rubber skin. Secondly, we presented the fabrication by utilizing not only the HF rubber but our previously proposed rubber vulcanization and adhesion techniques with electrolytic polymerization. Thirdly, we conducted a mechanical and thermal sensing touch experiment with the finger. As a result, it demonstrated that intelligence as a mechanoreceptor or thermoreceptor depends on its fabric: the HF rubber sensor mimicked Krause and bulbs has the thermal and pressing sensibility, and the one mimicked Ruffini endings the shearing sensibility.

To satisfy the requirement of haptic sensibility in rubber such as in the proposed hybrid skin (H-Skin), the authors have demonstrated a new method for solidifying rubber using electrolytic polymerization together with configured magnetic clusters of magnetic compound fluid (MCF) incorporated into the rubber by the application of a magnetic field. However, the rubber and magnetic fluid (MF) involved in the MCF rubber were water-soluble. In addition, the authors have demonstrated the practicability of using electrolytic polymerization with an emulsifier, polyvinyl alcohol (PVA), in which natural rubber (NR) or chloroprene rubber (CR) and silicone rubber (Q) can be mixed as water-soluble and water-insoluble rubbers, respectively. In this study, to enhance production, the feasibility of solidifying rubber by electrolytic polymerization is verified using varied water-insoluble rubber, varied water-insoluble MF, and varied surfactants to aid emulsion polymerization, except in the case of other kinds of rubber and MF which have been demonstrated until recent by the authors. Based on these diverse constituents, the authors propose a consummate fabrication process for multi-layered MCF rubber, which involves porous stocking-like rubber that can be permeated by any liquid. The investigation of this application is presented in the sequential second report.

The present paper describes a measurement technique for phase-separated velocity profile measurements in the two-phase bubbly flow. The Ultrasonic Velocity Profiler (UVP) method which is nonintrusive measurement, is applied to obtain an instantaneous velocity profile of liquid and bubble separately by using only one resonant frequency. To achieve this target, developed algorithm, which can decompose frequency component of the Doppler signal affected by liquid and bubble, is applied in the UVP system to obtain and separate instantaneous velocity profile of both phases. For confirming the applicability of modified measurement system, the developed UVP was used for the measurement of the velocity profile in bubbly flow on vertical pipe flow apparatus, the measurement accuracy was validated by UVP Original and Particle Image Velocimetry (PIV) method. Finally, the UVP was applied to experiment for observing velocity distribution of both phases in a bubble column.

Expanding on our previous report, we investigate the stability of a magnetic compound fluid (MCF) rubber sensor that was developed for a variety of engineering applications. To stabilize this sensor, we proposed a novel combination technique that facilitates the addition of dimethylpolysiloxane (PDMS) to natural rubber (NR)-latex or chloroprene rubber (CR)-latex using polyvinyl alcohol (PVA) by experimentally and theoretically investigating issues related to instability. This technique is one of several other novel combinations of diene and non-diene rubbers. Silicone oil or rubber with PDMS can be combined with NR-latex and CR-latex because of PVA’s emulsion polymerization behavior. In addition, owing to electrolytic polymerization based on the combination of PDMS and PVA, MCF rubber is highly porous and can be infiltrated in any liquid. Hence, the fabrication of novel intelligent rubbers using any intelligent fluid is feasible. By assembling infiltrated MCF rubber sheets and by conducting electrolytic polymerization of MCF rubber liquid with a hydrate using the adhesive technique as presented in a previous paper, it is possible to stabilize the MCF rubber sensor. This sensor is resistant to cold or hot water as well as γ-irradiation as shown in the previous report.