Hydrogels are promising materials for electronic skin due to their flexibility and modifiability. Reported hydrogel electronic skins can recognize stimulations and output signals, but the single output signal and the requirement of external power source limit their further applications. In this study, inspired by the neuron system, the self-powered neuron system-like hydrogels based on gelatin, water/glycerin and ionic liquid modified metal organic frameworks (MOFs) are prepared. The optimized hydrogel exhibits excellent adhesion (40 kPa), stretchability (0%-100%), water retention (>92% at 0% relative humidity (RH) atmosphere), ionic conductivity (>10 −3 S m −1 ) and stability (>30 days). Besides, the neuron system-like hydrogels are highly sensitive to pressure (0-10 N) and humidity (0%-75% RH) with dual-modal output, without external power source. Finally, the optimized hydrogel ionic skin is applied in human motion detection, energy harvesting, and low humidity sensing. This study provides a preliminary exploration of self-powered ionic skin for multi-application scenarios.
Abstract:The surface characteristics, such as wettability and roughness, play an important role in heat transfer performance in the field of microfluidic flow. In this paper, the process of a hot liquid flowing through a microchannel with cold walls, which possesses different surface wettabilities and microstructures, is simulated by a transient double-distribution function (DDF) two-phase thermal lattice Boltzmann BGK (LBGK) model. The Shan-Chen multiphase LBGK model is used to describe the flow field and the independent distribution function is introduced to solve the temperature field. The simulation results show that the roughness of the channel wall improves the heat transfer, no matter what the surface wettability is. These simulations reveal that the heat exchange characteristics are directly related to the flow behavior. For the smooth-superhydrophobic-surface flow, a gas film forms that acts as an insulating layer since the thermal conductivity of the gas is relatively small in comparison to that of a liquid. In case of the rough-superhydrophobic-surface flow, the vortex motion of the gas within the grooves significantly enhances the heat exchange between the fluid and wall.
Construction of an airport runway makes the impervious area of the airport high, which leads to the deterioration of the water environment and frequent waterlogging disasters. The selection of sponge airport facilities (e.g., pump, multi-functional storage tanks, green roof) to mitigate airport flooding has been a crucial issue in China. This study aims to develop a conceptual rainwater-runoff simulation model, which can take into account the effects of such facilities of a sponge airport. Taking catchment N1 of Beijing Daxing Airport as a case study, SWMM 5.1 was implemented to develop three sponge airport models (one pump, two pumps, combination of pump and multi-functional storage tanks). A sensitivity analysis was carried out to guarantee the robustness of the developed models. A 1-hour rainfall scenario with a 5-year return period was employed on the three sponge airport models. The results showed that the effect rankings of the control strategies on the water depth, volume and peak inflow of catchment N1 were comparable – combined strategies (combination of pump and multi-functional storage tanks) > one pump and two pumps. The conceptual and hydrological models developed in this study can serve as a simulation tool for implementing a real-time rainwater drainage control system in Beijing Daxing Airport.
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