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EMI announces the winners of prestigious mechanics awards

Confined thin shells, films and membranes are prone to lose stability to relieve the in-plane compression energy, which is traditionally regarded as a first route towards catastrophic failure [1]. From another perspective, this buckling behavior can be harnessed to realize certain functionality with the burgeoning use of extremely deformable materials and structures [2][3][4], such as the synthetic camouflaging skins via programmable wrinkling textures [5], shape-morphing of soft robotics actuators [6], bifurcation-guided printing of autonomous actuation [7], shape-programmable multistable surfaces [8], dynamic tuning of wrinkle-patterned topographies [9], and adaptive aerodynamic drag control [10]. Manipulation of reversible instability response, especially the flexible transition between buckling and stabilization regimes, would be a key for relevant applications. Such control can provide insights into fabricating topology-related functional membranes in broad applications.

Curvature and mechanics are intimately connected in thin objects. Curvature in conforming materials to rigid substrates can guide the self-assembly of defects such as crack paths [11] and pleats [12][13][14]. Surface curvature plays a key role in wrinkling pattern selection and morphological transition in core-shells [15][16][17][18][19] and curved film/substrate systems [20][21][22]. Spontaneous curvature can induce rotational symmetry-breaking buckling and snapping instability in thin shells [23][24]. Yet curvature can hold a delaying effect on the formation of wrinkles in a homogeneous growing system [25], and instabilities occur first in regions with the lowest curvature in a heterogeneous system for the morphogenesis of developing mammalian brain [26]. Combining curvature and cuts can realize wave propagation in kirigami structures [27] and network construction of curvy filamentary structures leads to a bending-stretching transition of deformation mode under tension [28]. Understanding the mechanism of curvature effects on morphological evolution and pattern formation is, in fact, crucial for the effective use of wrinkling as a tool for realizing multifunctional surfaces.

This month jClub is intended to initiate and encourage discussion on curvature-affected instability phenomena in membranes, surfaces and slender structures. Other influencing factors such as growth, medium and photo are also involved. Former jClubs on instability of soft materials are listed here for reference, e.g., by T. ZhangS. RudykhP. Rothemund, etc. Here, we provide a few recent illustrative examples from the large body of relevant works on this vibrant topic.

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