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pH sensing facilitates many substantial aspects of the society such as chemical laboratory analysis, agriculture, or water and soil qualities. However, existing pH sensors have problems and limitations such as fragility, hysteresis, or slow responding time. In this research, a new method utilizing fluorocarbon thin film via fluorine termination and boron‐doped diamond (BDD) solution‐gate field‐effect transistors (SGFETs) for pH sensing is developed for the first time. The fluorocarbon film device demonstrates a high pH sensitivity of 67.4 and 34.9 mV pH−1 in acid and alkaline pH regions, respectively.

Diamond has many appealing properties, including biocompatibility, ease of surface modification, and chemical–physical stability. In this study, the temperature dependence of the pH-sensitivity of a oxygen-terminated boron-doped diamond solution gate FET (C-O BDD SGFET) is reported. The C-O BDD SGFET operated in an electrolyte solution at 95 °C. At 80 °C, the pH sensitivity of C-O BDD SGFET dropped to 4.27 mV/pH. As a result, we succeeded in developing a highly sensitive pH sensing system at −54.6 mV/pH at 80 °C by combining it with a highly pH sensitive stainless-steel vessel.

The single-point compression principle, based on the collision of pulsed supermulti-jets, which is proposed in our previous reports, has the potential of obtaining both a high compression ratio and relatively low combustion noise, leading to a lower exhaust gas temperature, i.e., high thermal efficiency for the next generation of engines. The supermulti-jets also enclose high-temperature combustion gas around the chamber center, which means less heat loss to the chamber wall, i.e., higher thermal efficiency due to the air-insulation effect. Here, experimental and computational visualizations around the compression point should be examined in order to confirm the occurrence of single-point compression. Thus, in the present paper, we present experimental Schlieren photographs of flows formed by the collision of supermulti-jets without combustion and the results of unsteady three-dimensional computations conducted with the compressible Navier-Stokes equations, while the Cubic Interpolated pseudo-Particle (CIP) and Combined Unified Procedure (CUP) method is employed as numerical algorithm. Comparison of the experimental and computational results show fairly good agreement in time and space. Schlieren photographs and computational visualizations obtained for various conditions of four-, eight-, and sixteen-nozzles of jets are axial symmetrical, which will indicate the single-point compression based on the collision of supermulti-jets. Computations for asymmetrical distribution of seven nozzles also bring results showing nearly symmetric flow.

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