excessively cold sensations. [5] In contrast, hydrophobic textiles such as polyester can repel water on the outside, [6] but are useless against sweat on the inside. In recent years, considerable efforts have been made to improve the sweat transport through textiles, such as doublelayer hydrophobic/hydrophilic fabrics, [7] cotton fabrics printed with fluorocarbonbased hydrophobic finishes, [8] trilayered polyurethane/ (polyurethane-hydrolyzed polyacrylonitrile-SiO 2 )/ hydrolyzed polyacrylonitrile-SiO 2 fibrous membranes, [9] and biomimetic fibrous Murray membrane. [10] However, not much attention was paid to the dissipation of heat during the sweat transporting process. Since textiles thermal insulation can decrease, and the amount of reduction varies from 2 to 8% as related to water accumulation within textiles, [11] even resulting in hypothermia. Therefore, the development of a new functional textile to achieve efficient sweat transport and prevent undesired excessive cold is urgently needed.Directional water transport is a common phenomenon widely found in nature. [12] For example, spider silk with periodic conical spindle knots can drive water droplets toward spindle knots, [13] cactus spines can transport water directionally due to the curvature gradient on the surface of the spine, [14] and shorebirds can transport prey-laden water droplets toward their mouth by opening and closing their beaks. [15] These interesting phenomena of directional water transport originate from their unique asymmetric gradient structures. Therefore, construction of an asymmetric surface structure may be a method for designing functional textiles with effective sweat transport capability.Herein, we fabricated a hydrophobic/superhydrophilic Janus polyester/nitrocellulose textile with asymmetric hydrophilic conical micropores for directional liquid transport by a simple laser perforation method (Figure 1). This Janus polyester/ nitrocellulose textile can unidirectionally pump the excessive sweat from the hydrophobic layer to the superhydrophilic layer through asymmetric hydrophilic conical micropores from large to small (LTS) openings, thereby avoiding undesired sticky and excessive cold sensations from sweat. This study provides new information for the development of functional textiles that effectively manage excess sweat for comfortable skin microenvironments.A Janus polyester/nitrocellulose membrane is a kind of commercially available material that is widely used in microfluidic Excessive sweat secreted from the skin often causes undesired adhesion from wetted textiles and cold sensations. Traditional hydrophilic textiles such as cotton can absorb sweat but retain it. A hydrophobic/ superhydrophilic Janus polyester/nitrocellulose textile embedded with a conical micropore array with a hydrophilic inner surface that can achieve directional liquid transport (with an ultrahigh directional water transport capability of 1246%) and maintain human body temperature (2-3 °C higher than with cotton textiles) is demonstrated. When the hydr...

dressing for its intrinsic hydrophilicity. The left biofluid continuously hydrates the wound and complicates the healing process. [7] Therefore, it is urgently needed to develop a new wound dressing to effectively remove the excessive biofluid.Bio-interface plays a significant role in the interaction between biofluid and biomaterial. [8] Surface wettability of wound dressings can generally affect the wetting behavior of biofluid around wounds. Hydrophilic materials, like most conventional dressings, easily get wetted by biofluid thus overhydrating wound. [7] In contrast, as the waterproof outer layer of dressings, hydrophobic materials prevent unexpected contacting of external fluid with the wounds, but they cannot facilitate biofluid removal. [9][10][11] Recently, several materials with asymmetric wettability have shown their unique capability to transfer water droplet, for instance, a polyester fabric with wettability gradient, [12] a polyurethane (PU)/polyvinyl acetate composite fibrous film, [13] and a one-side fluorinated cotton fabric membrane. [14] Therefore, the control of surface wettability may offer an opportunity to design wound dressings with the capability of effective biofluid management.Herein, we electrospan a hydrophobic PU nanofiber array onto a hydrophilic microfiber network, constructing a selfpumping dressing as a biofluid pump (Figure 1a). Such a selfpumping dressing can unidirectionally drain the excessive biofluid from its hydrophobic side to hydrophilic side, thereby preventing the biofluid from wetting the wound. In an infected wound model, we demonstrated a faster wound healing treated by this self-pumping dressing than the conventional dressing. This study provides a new clue to manage excess biofluid around wounds to promote faster wound healing.Medical gauze is a conventional dressing for its economic cost, flexible and tough network structure, and super absorbing capability. [15] Bundles (diameter = 259.0 ± 59.3 µm) of cotton microfibers (diameter = 16.9 ± 2.6 µm) interpenetrate each other (Figure 1b-d) and form a superhydrophilic network (Figure 1d, inset) in medical gauze, suitable for serving as a supporting framework and the source of pumping force as well. PU is a hydrophobic (Figure 1g, inset) biocompatible medical material with easy processing property, [16] expected to be an ideal candidate for preparing a separate layer to prevent biofluid wetting. Here we electrospan a thin layer of hydrophobic PU nanofiber array (diameter = 220.0 ± 40.0 nm; Figure 1e-g) onto a cotton medical gauze (Figure 1b-d) to form a self-pumping dressing Excessive biofluid around wounds often causes infection and hinders wound healing. However, the intrinsic hydrophilicity of the conventional dressing inevitably retains excessive biofluid at the interface between the dressing and the wound. Herein, a self-pumping dressing is reported, by electrospinning a hydrophobic nanofiber array onto a hydrophilic microfiber network, which can unidirectionally drain excessive biofluid away from wounds and finall...

This paper presents observations of postsunset super plasma bubbles over China and adjacent areas during the second main phase of a storm on 8 September 2017. The signatures of the plasma bubbles can be seen or deduced from (1) deep field‐aligned total electron content depletions embedded in regional ionospheric maps derived from dense Global Navigation Satellite System networks, (2) significant equatorial and midlatitudinal plasma bite‐outs in electron density measurements on board Swarm satellites, and (3) enhancements of ionosonde virtual height and scintillation in local evening associated with strong southward interplanetary magnetic field. The bubbles/depletions covered a broad area mainly within 20°–45°N and 80°–110°E with bifurcated structures and persisted for nearly 5 hr (∼13–18 UT). One prominent feature is that the bubbles extended remarkably along the magnetic field lines in the form of depleted flux tubes, reaching up to midlatitude of around 50°N (magnetic latitude: 45.5°N) that maps to an altitude of 6,600 km over the magnetic equator. The maximum upward drift speed of the bubbles over the magnetic equator was about 700 m/s and gradually decreased with altitude and time. The possible triggering mechanism of the plasma bubbles was estimated to be storm time eastward prompt penetration electric field, while the traveling ionospheric disturbance could play a role in facilitating the latitudinal extension of the depletions.

Conventional adhesives often encounter interfacial failure in humid conditions due to small droplets of water condensed on surface, but spider silks can capture prey in such environment. Here a robust spider‐silk‐inspired wet adhesive (SA) composed of core–sheath nanostructured fibers with hygroscopic adhesive nanosheath (poly(vinylpyrrolidone)) and supporting nanocore (polyurethane) is reported. The wet adhesion of the SA is achieved by a unique dissolving–wetting–adhering process of core–sheath nanostructured fibers, revealed by in situ observations at macro‐ and microscales. Further, the SA maintains reliable adhesion on wet and cold substrates from 4 to −196 °C and even tolerates splashing, violent shaking, and weight loading in liquid nitrogen (−196 °C), showing promising applicability in cryogenic environments. This study will provide an innovative route to design functional wet adhesives.

Wearable devices have attracted a lot of attention because of their importance in the biomedical and electronic fields. However, as one of the important fixing materials, skin adhesives with controlled adhesion are often ignored. Although remarkable progress has been achieved in revealing the natural adhesion mechanism and biomimetic materials to complex solid surfaces, it remains a great challenge to explore nonirritant, controlled skin adhesives without surface structure. Herein, we present skin-adhesive patches of polydimethylsiloxanes (SAPs) with controlled adhesion by simply modulating polymer chain mobility at the molecular level. The controlled adhesion of SAPs strongly depends on the proportion of polymer chains with different mobility exposed to the solid surface, including free chains, dangling chains, and cross-linking chains. As a proof of concept, we demonstrate that the SAP can act as a skin-friendly fix to monitor the human pulse by integrating with the poly(vinylidene fluoride-trifluorethylene)/ reduced graphene oxide (P(VDF-TrFE)@rGO) nanofiber sensor. This study provides a clue to design durable and skin-friendly adhesives with controlled adhesion for wearable devices.

In this paper, we test whether time periods with hot proton temperature anisotropy are associated with electromagnetic ion cyclotron (EMIC) waves and whether the plasma conditions during the observed waves satisfy the linear theory threshold condition. We identify 865 events observed by the Composition Distribution Function instrument onboard Cluster spacecraft 4 during 1 January 2001 to 1 January 2011 that exhibit a positive temperature anisotropy (A hp = T ? h /T k h À 1) in the 10-40 keV protons. The events occur over an L range from 4 to 10 in all magnetic local times and at magnetic latitudes (MLATs) within ±50°. Of these hot proton temperature anisotropy (HPTA) events, only 68 events have electromagnetic ion cyclotron (EMIC) waves. In these 68 HPTA events, for those at 3.81.0 nT 2 /Hz mainly appear in the region with f EMIC /f H,eq < 0.8. Two stop bands are present, one near the region with f EMIC /f H, eq ≈ 0.33, the other in the region with 0.8 < f EMIC /f H,eq < 0.9. Most of the EMIC waves in the He, H, and >H bands satisfy A hp /(A hp + 1) > f EMIC /f H,lo , A hp /(A hp + 1) > 0.45 Â f EMIC /f H,lo , and A hp /(A hp + 1) < 0.45 Â f EMIC /f H,lo . f EMIC , f H,eq , and f H,lo are the EMIC wave frequency, the magnetic equatorial, and the local proton gyrofrequencies. We also find that the EMIC waves predominantly occur with A hp > 0.25. By testing a threshold equation for the EMIC instability based on linear theory, we find that for EMIC waves with |MLAT| ≤ 10°in the He, H, and >H bands, the percentages that satisfy the predicted conditions for wave growth by the threshold equation are 15.2%, 24.6%, and 25.6%. For the EMIC waves with |MLAT| > 10°the percentages that satisfy the wave growth predicted conditions are only 2.8%, 2.6%, and 0.0%. Finally, possible reasons for the low forecast accuracies of EMIC waves are suggested.

In this letter we consider a wireless-powered backscatter communication (WP-BackCom) network, where the transmitter first harvests energy from a dedicated energy RF source (S) in the sleep state. It subsequently backscatters information and harvests energy simultaneously through a reflection coefficient. Our goal is to maximize the achievable energy efficiency of the WP-BackCom network via jointly optimizing time allocation, reflection coefficient, and transmit power of S. The optimization problem is non-convex and challenging to solve. We develop an efficient Dinkelbach-based iterative algorithm to obtain the optimal resource allocation scheme. The study shows that for each iteration, the energy-efficient WP-BackCom network is equivalent to either the network in which the transmitter always operates in the active state, or the network in which S adopts the maximum allowed power.

Ambient backscatter communications (AmBack-Coms) have been recognized as a spectrum-and energy-efficient technology for Internet of Things, as it allows passive backscatter devices (BDs) to modulate their information into the legacy signals, e.g., cellular signals, and reflect them to their associated receivers while harvesting energy from the legacy signals to power their circuit operation. However, the co-channel interference between the backscatter link and the legacy link and the nonlinear behavior of energy harvesters at the BDs have largely been ignored in the performance analysis of AmBackComs. Taking these two aspects, this paper provides a comprehensive outage performance analysis for an AmBackCom system with multiple backscatter links, where one of the backscatter links is opportunistically selected to leverage the legacy signals transmitted in a given resource block. For any selected backscatter link, we propose an adaptive reflection coefficient (RC), which is adapted to the non-linear energy harvesting (EH) model and the location of the selected backscatter link, to minimize the outage probability of the backscatter link. In order to study the impact of co-channel interference on both backscatter and legacy links, for a selected backscatter link, we derive the outage probabilities for the legacy link and the backscatter link. Furthermore, we study the best and worst outage performances for the backscatter system where the selected backscatter link maximizes or minimizes the signal-tointerference-plus noise ratio (SINR) at the backscatter receiver. We also study the best and worst outage performances for the legacy link where the selected backscatter link results in the lowest and highest co-channel interference to the legacy receiver, respectively. Computer simulations validate our analytical results, and reveal the impacts of the co-channel interference and the EH model on the AmBackCom performance. In particular, the cochannel interference leads to the outage saturation phenomenon in AmBackComs, and the conventional linear EH model results in an over-estimated outage performance for the backscatter link.