The influence of injection pressure up to ultra-high value of 300 MPa , nozzle hole diameters of 0.16 and 0.08 mm and fuel properties such as boiling point, cetane number and oxygen content on spray, ignition and combustion characteristics of biodiesel fuel in diesel engine were investigated. Biodiesel from palm oil source (BDF) and for comparison the JIS #2 diesel fuel were utilized. The Mie-scattering technique was used for characterizing the evaporating spray formation processes while the OH chemiluminescence technique was used to determine the ignition and the lift-off length of the combusting flame. Furthermore, the two color pyrometry was applied to study the soot formation processes. The results obtained indicated that due to higher boiling point, the BDF produced longer liquid phase length as compared to diesel. It was observed that the ignition region was larger for the 0.16mm nozzle as compared to the 0.08 mm. Due to the enhanced mixing processes, ignition delay decreased as the injection pressure increased from 100 to 300 MPa respectively and also by reducing the nozzle hole diameter to 0.08 mm. Higher cetane number and oxygen content of the BDF facilitated shorter ignition delay as compared to diesel. The percentage stoichiometry air entrained increased by decreasing the nozzle hole diameter. The BDF flame produced shorter lift-off length and lower percentage stoichiometry air. Under higher injection pressures and decreasing nozzle diameter, the BDF produced less soot as compared to diesel. The fuel oxygen content in the biodiesel fuel played a greater role in the soot formation processes.

Flexible electronics are playing an increasingly important role in human health monitoring and healthcare diagnosis. Strong adhesion on human tissue would be ideal for reducing interface resistance and motion artifacts, but arising problems such as skin irritation, rubefaction, and pain upon device removal have hampered their utility. Here, inspired by the temperature reversibility of hydrogen bonding, a skin-friendly conductive hydrogel with multiple-hydrogen bonds was designed by using biocompatible poly(vinyl alcohol) (PVA), phytic acid (PA), and gelatin (Gel). The obtained PVA/PA/Gel (PPG) hydrogel with temperature-triggered tunable mechanic could reliably adhere to skin and detect electrophysiological signals under a hot compress while be readily removed under a cool compress. Furthermore, the additional advantages of transparency, breathability, and antimicrobial activity of the PPG hydrogel ensure its long-time wearable value on the skin. It is both environmentally friendly and cost saving for the waste PPG hydrogel during production can be recycled based on their reversible physical bonding. The PPG hydrogel sensor is expected to have good application prospects to record electrophysiological signals in human health monitoring.

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Sweat contains a broad range of critical biomarkers including ions, small molecules, and macromolecules that may indirectly or directly reflect the health status of the human body and thereby help track disease progression. Wearable sweat biosensors enable the collection and analysis of sweat in situ, achieving real-time, continuous, and noninvasive monitoring of human biochemical parameters at the molecular level. This review summarizes the physiological/pathological information of sweat and wearable sweat biosensors. First, the production of sweat pertaining to various electrolytes, metabolites, and proteins is described. Then, the compositions of the wearable sweat biosensors are summarized, and the design of each subsystem is introduced in detail. The latest applications of wearable sweat biosensors for outdoor, hospital, and family monitoring are highlighted. Finally, the review provides a summary and an outlook on the future developments and challenges of wearable sweat biosensors with the aim of advancing the field of wearable sweat monitoring technology.

Increasing the injection pressure and downsizing the nozzle orifice diameter have been major measures for diesel engines to facilitate fuel-ambient gas mixture formation and combustion processes. The objective of this investigation is to carry out a quantitative analysis on the effects of micro-hole nozzle and ultra-high injection pressure on the mixing and combustion characteristics of diesel spray flame. Hence, laser-induced fluorescence and particle image velocimetry technique was employed to quantitatively access the gas entrainment of diesel spray emerging from nozzle with orifice diameter down to 80 mm under injection pressure up to 300 MPa, together with OH* chemiluminescence imaging and two-color pyrometry techniques to resolve the combustion and soot formation processes. Additionally, numerical simulation on the multi-phase flow inside injector nozzle was conducted to obtain information on internal flow dynamics. Experimental results show that over 80% of the ambient gas entrained into a spray plume is through the capturing effect at its tip, followed by the entraining effects at its peripheral boundary. Moreover, both a decrease in orifice diameter and an increase in injection pressure result in enhancement of the instantaneous gas to fuel mass flow rate ratio, shortening of liquid length of spray under evaporating conditions. The lift-off length of a diesel spray flame is substantially extended by the increase in injection pressure, and slightly shortened by the decrease in nozzle orifice diameter. Additionally, the numerically acquired velocity and turbulence data at the nozzle exit plane provide interpretation on the variations of liquid length and lift-off length under different injection conditions. Finally, the combination use of micro-holes and ultra-high injection pressure greatly accelerate the mixing of fuel and ambient gas, avoiding the interference of liquid length and liftoff length, and drastically decreasing the soot formation.