Abstract Stretchable conductive fibers can be directly woven into textiles and applied in wearable and implantable electronic devices. However, for a stretchable conductive fiber that is capable of safely using in full water environment with strains when contacting to skin, it is challenging. Herein, an ultrafine core–sheath stretchable conductive fiber (CSCF in short) with insulative outer sheath and conductive inner core is designed particularly for safe underwater electronic skin devices. CSCF starts from prestrained Lycra fiber followed by spray coating 1D conductive species (carbon nanotubes (CNTs)/silver nanowires (AgNWs)) and wrapping styrene‐(ethylene‐butylene)‐styrene (SEBS) thin film. CSCF exhibits stable core conductivity (e.g., R 0 ≈ 2 × 10 4 S m −1 , Δ R/R 0 ≈ 0.1 at 100% strain) as well as surface insulation upon mechanical stretching in full water environment. The thickness‐tunable SEBS not only protects skin away from leak of CNTs and AgNWs, but also efficiently suppresses leakage current to an extremely safe level (<1 µA at 5 V) when applying in underwater electronic skin devices. A wireless charging patch composed by CSCF induction coil is able to light light emitting diode (LEDs) no matter when CSCFs are folding and stretching in water. These advantages highlight the promising application of stretchable conductive fiber with protective polymer skin for safe underwater wearable electronics.
Abstract Epidermal biopotential monitoring is an essential part of wearable healthcare. For 24 × 7 h detection of electrophysiological signals, commercialized gel electrodes cannot satisfy the demands, in particular for monitoring in humidity or underwater. Epidermal electrodes that can be stable and operated underwater are required. Here, a highly conductive and optically camouflaged ionic skin for epidermal biopotential monitoring under aquatic circumstances is designed. There is a fluorine‐dipole interaction system consisting of fluorine‐rich segment in the polyurethane backbone and fluorine‐cation bonded 1‐ethyl‐3‐methylimidazolium bis(trifluoromethyl‐sulfonyl) imide ([EMIM] + [TFSI] − ) ion pairs distributed in the polymer matrix. Benefitting from the fluorine‐cation interaction, the ionic skin gains remarkable ionic conductivity (1.04 × 10 −3 S cm −1 ), high optical transmittance (92%), and improved mechanical strength (3.1 MPa of Young's modulus). Via cations caught by fluorine‐rich segments, its ionic conductivity can keep stable even by rinsing or fierce washing in water. The epidermal electrode based on such ionic skin can accurately measure a variety of electrophysiological signals undboth atmospheric and aquatic environments, exhibiting robust and excellent signal quality. As the first demonstration of ionic skin‐based electrophysiological electrodes, the ionic skin paves a new way for all‐day wearable healthcare.
With the global crisis of resources and environment, and the ecological environment is on destruction，all countries in the world have started to develop green building evaluation system, so the concept of green building evaluation system comes into being. In this paper, according to the research on LEED and Evaluation Rulers for Green Building of China, and basing on the planning and construction status of Eco-city, it is analyzed and evaluated by applying the two green building evaluation systems. According to the research on the two green building systems and the excellent case of the Eco-city, the paper hopes that it can supply some reference values for developing green building in the developing countries.
The relationships between vegetation and environmental factors have always been a core concern of ecologists. The dynamic characteristics of plant communities during the growing season can directly reflect these relationships, so we examined this issue for three typical ecosystems on the Tibetan Plateau. During the growing season, the dominant species remained stable while non-dominant species changed significantly in the alpine meadow and alpine steppe and a mono-dominant community was found in the temperate desert shrub. Due to the seasonal variations of temperature and soil water content, plant species diversity varied significantly during the growing season. Patrick richness, Pielou evenness and Simpson diversity indices differed significantly in the alpine meadow and alpine steppe. The total biomass of these three ecosystems was the largest during the middle growing season. Biomass was greater in the alpine meadow than the alpine steeps or temperature desert. The root-to-shoot ratio was the lowest during the middle growing season for the alpine meadow and alpine steppe and largest during the early growing season for temperate desert shrub. RDA showed the belowground and total biomass were greatly affected by soil physicochemical factors. Multiple linear stepwise regression showed the above ground biomass was greatly affected by relative atmospheric humidity and belowground and total biomass were greatly affected by soil organic carbon, total nitrogen at 0–20 cm soil depth and pH at 10–20 cm soil depth. These findings provide insights into understanding the relationships between vegetation and environmental factors and promote the sustainable utilization of local grasslands on the Tibetan Plateau.
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