1. Hygroscopically responsive bilayer structures.
Hygroscopically responsive bilayer structures. (A) Optical image of a seed of P. carnosum and the SEM image of the cross-section of its awn. (B) Time for saturation of deflection angle versus thickness of active layers fabricated via spin-coating (red circles), random electrospinning (yellow circles), and directional electrospinning (blue circles). The thickness of the inactive layer is 55 μm for all the cases. The trend lines for all the types of active layer follow ts ~ h2, implying the diffusive transport of moisture in the layers. Inset: Temporal evolution of the deflection angle at the free end of the bilayers, 25 mm in length, whose active layers are fabricated by spin-coating (red circles), random electrospinning (yellow circles), and directional electrospinning (blue circles). The active layer thickness is 35 μm. (C) Coordinate system for the bilayer. (D) Temporal evolution of the bilayer curvature when the environmental humidity abruptly increases to 0.8 from 0.2 at t = 0. Circles and lines correspond to experiment and theory, respectively. Error bars represent SD.
Beomjune Shin et al. Sci. Robotics 2018;3:eaar2629
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