Adjustable rigidity has been a perennial challenge for composite materials. Inspired by biomineralization, a rigidity–flexibility reversible switching material (RFRS) based on wood framework is introduced in this study. RFRS uses a singular, pH-responsive mineralization strategy, with amorphous calcium phosphate as the mineralization precursor. Using water as a medium, RFRS can undergo reversible transitions between two states—hard (rigidity) and soft (flexibility)—in response to water stimulation. In its dry state, RFRS exhibits excellent mechanical performance, with transverse and longitudinal Shore D values increase by 28.4 times and 3.15 times, respectively. In the wet state, it demonstrates excellent capability for shape recovery. The rate of dimensional change for RFRS is close to 0 % under 70 % compression deformation. RFRS also exhibits reversible switching stability between dry–hard and wet–soft states. The transverse and longitudinal Shore D values are only 36.6 % and 47.3 % of their initial values after 10 dry–wet cycles; nonetheless, the material maintains a high capability for reversible switching between rigidity and flexibility. A smart material with adjustable rigidity is developed from the perspective of biomimetic minerals in this study, contributing to the exploration of innovative research perspectives.

中文翻译：

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一种仿生矿化木质复合材料，具有水介导的干-刚度和湿-柔韧性之间的可逆切换


可调节刚度一直是复合材料面临的长期挑战。受生物矿化作用的启发，本研究引入了一种基于木框架的刚性-柔韧性可逆开关材料 （RFRS）。RFRS 使用单一的、pH 响应的矿化策略，以无定形磷酸钙作为矿化前体。使用水作为介质，RFRS 可以在两种状态（硬（刚性）和软（柔韧性））之间发生可逆转变，以响应水的刺激。在干燥状态下，RFRS 表现出优异的机械性能，横向和纵向邵氏 D 值分别增加了 28.4 倍和 3.15 倍。在湿态下，它表现出优异的形状恢复能力。在 70% 的压缩变形下，RFRS 的尺寸变化率接近 0%。RFRS 还在干-硬和湿-软状态之间表现出可逆的开关稳定性。经过 10 次干湿循环后，横向和纵向邵氏 D 值仅为初始值的 36.6 % 和 47.3 %;尽管如此，该材料仍具有在刚度和柔韧性之间可逆切换的高能力。本研究从仿生矿物的角度开发了一种刚度可调的智能材料，有助于探索创新的研究视角。