Stretchable conductive fibers have attracted much attention due to their potential use in wearable electronics. However, the ultra-high strain insensitive conductivity is hindered by mechanical mismatch in Young’s modulus and failure of stretchable structures under large deformation. This challenge is addressed with a conductive and elastic multifilament made of the polyurethane monofilaments that are surface-coated with buckled polypyrrole (PPy) of which flexibility is improved by sodium sulfosalicylate. Such parallel conductive monofilaments with PPy buckling on surface reduce the influence of cracks in the conductive coating on the overall conductivity, displaying an ultra-high strain insensitive behavior (quality factor Q = 10.9). Remarkably, various complex forms of wearable electronic textiles made by this conductive multifilament maintain the strain-insensitive behavior of the original multifilament, even upon the large deformation of human joint. This multifilament with wrinkled PPy has attractive advantages in the application of super-stretched wearable electronic devices.
Stretchable
and durable conductors are significant to
the development
of wearable devices, robots, human–machine interfaces, and
other artificial intelligence products. However, the desirable strain-insensitive
conductivity and low hysteresis are restricted by the failure of stretchable
structures and mismatch of mechanical properties (rigid conductive
layer and elastic core substrate) under large deformation. Here, based
on the principles of fractal geometry, a stretchable conductive fiber
with hierarchical wrinkles inspired by the unique shape of the maple
leaf was fabricated by combining surface modification, interfacial
polymerization, and improved prestrain finishing methods to break
through this dilemma. The shape and size of wrinkles predicted by
buckling analysis via the finite element method fit well with that
of actual wrinkles (30–80 μm of macro wrinkles and 4–6
μm of micro wrinkles) on the fabricated fiber. Such hierarchically
wrinkled conductive fiber (HWCF) exhibited not only excellent strain-insensitive
conductivity denoted by the relative resistance change ΔR/R
0 = 0.66 with R
0 the original resistance and ΔR the
change of resistance after the concrete strain reaching up to 600%,
but also low hysteresis (0.04) calculated by the difference in area
between stretching and releasing curve of the ΔR/R
0 strain under 300% strain and long-term
durability (>1000 stretching–releasing cycles). Furthermore,
the elastic conductive fiber with such a bionic structure design can
be applied as highly stretchable electrical circuits for illumination
and monitors for the human motion under large strains through tiny
and rapid resistance changes as well. Such a smart biomimetic material
holds great prospects in the field of stretchable electronics.
Although both hyperprocoagulant status, characterized by elevated thrombin levels, and vascular endothelial growth factor (VEGF) resistance, marked by attenuated expression of VEGFR2 (also called FLK1 or KDR), are known to contribute importantly to an increased risk of vascular events in diabetes mellitus type 2 (T2DM), it remains obscure whether these two biological events regulate angiogenic response in a coordinated manner. We show here that endothelial expression of hepatocyte nuclear factor 4α (HNF4α) was significantly upregulated in rodents and humans with T2DM, and HNF4α upregulation by thrombin was dependent on activation of multiple pathways,
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