Insights into the microstructures of hygroscopic movement in plant seed dispersal

Fracture of the dimorphic fruits ofAethionema arabicum(Brassicaceae)

“…Our working hypothesis is that the highly coordinated events causing tissue separation and endocarp lignification create spring-like tensions in the mature DEH fruit, the elastic energy from which is retained during the dry period until rain-induced (ombrohydrochory) impact events cause "pod-shattering" and M + seed dispersal to occur. This is consistent with the passive, drying forces acting on microstructures that have been demonstrated during fruit and seed dispersal of other species (Elbaum and Abraham 2014). For example, the shedding of living twigs (in Salix spp.…”

High‐Power Actuation from Molecular Photoswitches in Enantiomerically Paired Soft Springs

“…The variety of movements seen in the plant and animal kingdoms have provided inspiration for the engineering of soft robots of all kinds,9, 10, 11, 12, 13, 14 and in particular, the realization that plant mechanics often rely on dynamic helical systems15, 16, 17, 18, 19 has motivated the development of a variety of chiral actuators where molecules were used either as active transducers of energy11, 13, 20, 21 or as relays for humidity or temperature changes 22, 23, 24, 25. These soft actuators have demonstrated reversible shape transformation, work, and motility,26 but the response speed and power produced remain moderate, mainly owing to the lack of mechanisms to drive non‐linear actuation 27.…”

“…Plant pods typically feature a flat hull comprising two narrow sides, with two fibrous layers oriented at angles of +45° and −45° with respect to the longitudinal axis of the pod (Figure 1 a). When the pod dries, each fibrous layer shrinks perpendicularly to its orientation, inducing mirror‐image saddle‐like curvatures and eventually a dramatic opening 17, 18, 32. In analogy, we use liquid‐crystal networks featuring periodically alternating bars.…”

“…The device is operated by isomerization of al ight-responsive molecular switch that drives the twisting of strips of liquid-crystal elastomers.T he strips twist in opposite directions and work against eacho ther until the pod pops open from stress.T his mechanism allows the photoisomerization of molecular switches to stimulate rapid shape changes at the macroscale and thus to maximizea ctuation power.Designing shape-morphing materials has become am ajor scientific challenge,w ith implications ranging from soft robotics [1][2][3] to realizing the full potential of artificial molecular machines. [4][5][6][7][8] Thevariety of movements seen in the plant and animal kingdoms have provided inspiration for the engineering of soft robots of all kinds, [9][10][11][12][13][14] and in particular, the realization that plant mechanics often rely on dynamic helical systems [15][16][17][18][19] has motivated the development of av ariety of chiral actuators where molecules were used either as active transducers of energy [11,13,20,21] or as relays for humidity or temperature changes. [22][23][24][25] These soft actuators have demonstrated reversible shape transformation, work, and motility, [26] but the response speed and power produced remain moderate,mainly owing to the lack of mechanisms to drive non-linear actuation.…”

“…When the pod dries,each fibrous layer shrinks perpendicularly to its orientation, inducing mirror-image saddle-like curvatures and eventually ad ramatic opening. [17,18,32] In analogy,w eu se liquid-crystal networks featuring periodically alternating bars. One set of bars is polymerized in alow liquid-crystalline order state (LO), and the elongation of these bars is consequently negligible under stimulation, whereas the other bars are polymerized while retaining ah igh liquid-crystalline order (HO);c onsequently they display anisotropic shape change under illumination (Figure 1b,c).Aliquid crystal was prepared by mixing trans-1 (Figure 1) with liquid-crystal monomers S1 (see the Supporting Information, Figure S1), an ematic liquid crystal S2 ( Figure S1), and ap hotoinitiator initiating polymerization with both UV and visible light.…”