Fibrous MXene Synapse-Based Biomimetic Tactile Nervous System for Multimodal Perception and Memory.

Biomimetic tactile nervous system (BTNS) inspired by organisms has motivated extensive attention in wearable fields due to its biological similarity, low power consumption, and perception-memory integration. Though many works about planar-shape BTNS are developed, few researches could be found in the field of fibrous BTNS (FBTNS) which is superior in terms of strong flexibility, weavability, and high-density integration. Herein, a FBTNS with multimodal sensibility and memory is proposed, by fusing the fibrous poly lactic acid (PLA)/Ag/MXene/Pt artificial synapse and MXene/EMIMBF4 ionic conductive elastomer. The proposed FBTNS can successfully perceive external stimuli and generate synaptic responses. It also exhibits a short response time (23 ms) and low set power consumption (17 nW). Additionally, the proposed device demonstrates outstanding synaptic plasticity under both mechanical and electrical stimuli, which can simulate the memory function. Simultaneously, the fibrous devices are embedded into textiles to construct tactile arrays, by which biomimetic tactile perception and temporary memory functions are successfully implemented. This work demonstrates the as-prepared FBTNS can generate biomimetic synaptic signals to serve as artificial feeling signals, it is thought that it could offer a fabric electronic unit integrating with perception and memory for Human-Computer interaction, and has great potential to build lightweight and comfortable Brain-Computer interfaces.

Electrically driven heartbeat effect of gallium-based liquid metal on a ratchet.

The realization of the liquid metal heartbeat effect shows better controllability under non-periodic stimuli than spontaneous oscillation or periodic stimuli. However, adjusting the liquid metal heartbeat performance, drop spreading area, and frequency, solely by the magnitude of the voltage, has great limitations. Here, we demonstrate that the eGaIn drop can beat inside graphite ring electrodes under DC voltage in alkaline solutions on ratchet substrates. These sawtooth structures provide asymmetric textures which influence liquid metal deformation during the beating of the heart. We achieved heartbeat frequencies from 2.7 to 4.8 Hz, a 100% increase in the tunable frequency range compared to that on a flat surface. The oxidative spreading of the eGaIn drop on the ratchet substrate shows that the drop penetrates into the grooves of the sawtooth structure. Moreover, we investigated the physical mechanisms affecting the eGaIn heartbeat frequency and the influence on the spreading area of the eGaIn drop at various sawtooth sizes and orientations. These findings not only enhance our understanding of droplet manipulation on sawtooth-structured surfaces but also facilitate the design of microfluidic pump systems.

[Seasonal Characteristics and Source Analysis of Water-soluble Inorganic Ions in PM2.5 in Suqian City].

To study the seasonal pollution characteristics and sources of water-soluble inorganic ions in atmospheric PM2.5 in Suqian City, 171 samples were collected at three monitoring points, which were in the water vapor channel, from May 2017 to January 2018. The mass concentrations of PM2.5 and nine water-soluble inorganic ions were analyzed. The results showed that the annual average concentration of water-soluble inorganic ions in PM2.5 in Suqian City was (44.08±34.61) µg ·m-3, accounting for 41.8% of PM2.5. The concentrations of these species were in the order of ρ(NO3-) > ρ(SO42-) > ρ(NH4+) > ρ(ρl-) > ρ(Na+) > ρ(Ca2+) > ρ(K+) > ρ(F-) > ρ(Mg2+); NO3-, SO42-, and NH4+ accounted for 75.6% of the total water-soluble ions. The annual average ratio of ρ(NO3-) to ρ(SO42-) was 1.53±0.88, indicating that mobile sources contributed more to PM2.5 pollution. Based on the correlation analysis of NH4+ and SO42-, NO3- may exist in the form of (NH4)2 SO4, NH4HSO4, or NH4NO3. According to the principal component analysis, secondary transformation, industrial pollution, biomass burning, and dust were the major sources of water-soluble inorganic ions. PM2.5concentrations were positively related to relative humidity in winter. Water vapor transmission is more likely to promote PM2.5 accumulation in winter.