Smart Soft Materials with Multiscale Architecture and Dynamic Surface Topographies

Smart soft materials have one or more characteristics that can be significantly altered in convertible fashions by external stimuli, such as light, moisture, mechanical force, temperature, electric/magnetic fields, pH, and so on. These materials can lead to widespread application in multifunctional smart devices. Recently, various smart soft materials have been developed under the inspiration of the intriguing multiscale structures, adaptive mechanisms, and dynamic responses of natural life, with an aim to further design advanced material systems with novel, intriguing, and unprecedented properties. Herein, inspired by the fascinating visual display strategies and adaptive mechanisms in animals and plants, we have fabricated a series of smart soft material-based devices that can respond to external stimuli with instantaneous and reversible fashions in optical, electrical, mechanical, and/or shape deformation signals. These devices can be fabricated for widespread applications, including smart windows, encryption devices, thermal camouflage, wearable strain sensors, anticounterfeit tabs, 3D stretchable electronics, dynamic displays, rewritable media, human- machine interfaces, and so on. The key to successfully achieving those intriguing characteristics in these smart material systems lies in the function-orientated structural design, which integrates bioinspired design and surface engineering with multiscale architecture as the crucial elements. In this Account, we provide a summary, with a main focus on our own work, of the recent advances in the bioinspired smart soft materials fabricated on the basis of 2D or 3D film-substrate multilayered structures. These materials are characterized by convertible topographies like dynamic cracks, folds, stimuli-responsive wrinkles, and other analogous structures. Those topographies are responsible for the dynamic stimuli-responsive optical, electrical, and mechanical properties demonstrated in the system, such as strain-dependent light scattering effect, mechanical tunable light shielding properties, moisture/mechanically/ photothermally tunable surface reflectance, moisture/mechanically responsive resistance, etc. Besides, those 2D functional materials can be further evolved into shape adaptive 3D structures via strain relaxation methods. These systems demonstrate high design flexibility, excellent reversibility, and wide applicability, which can pave new routes for designing next generation smart soft materials equipped with versatile, tunable, adaptable, and interactive stimuli-responsive properties.