Multifunctional materials and devices with captivating properties can be assembled from cellulose and cellulose-based composite materials combining functionality with structural performance. Cellulose is one of the most abundant renewable materials with captivating properties, such as mechanical robustness, biocompatibility, and biodegradability. Cellulose is a low-cost and abundant biodegradable resource, CO2 neutral, with a wide variety of fibers available all over the world. Over thousands of years, nature has perfected cellulose-based materials according to their needs, such as function vs. structure. Mimicking molecular structures at the nano-, micro-, and macroscales existing in nature is a great strategy to produce synthetic cellulose-based active materials. A concise background of cellulose and its structural organization, as well as the nomenclature of cellulose nanomaterials, are first addressed. Key examples of nature-designed materials with unique characteristics, such as “eternal” coloration and water-induced movement are presented. The production of biomimetic fiber and 2D fiber-based cellulosic materials that have attracted significant attention within the scientific community are represented. Nature-inspired materials with a focus on functionality and response to an external stimulus are reported. Some examples of 3D-printed cellulosic materials bioinspired, reported recently in the literature, are addressed. Finally, printed cellulosic materials that morph from a 1D strand or 2D surface into a 3D shape, in response to an external stimulus, are reported. The purpose of this review is to discuss the most recent developments in the field of “nature-inspired” cellulose-based active materials regarding design, manufacturing, and inspirational sources that feature existing tendencies.
Among the movements observed in some cellulosic structures produced by plants are those that involve the dispersion and burial of seeds, as for example in Erodium from the Geraniaceae plant family. Here we report on a simple and efficient strategy to isolate and tune cellulose-based hygroscopic responsive materials from Erodium awns’ dead tissues. The stimuli-responsive material isolated forms left-handed (L) or right-handed (R) helical birefringent transparent ribbons in the wet state that reversibly change to R helices when the material dries. The humidity-driven motion of dead tissues is most likely due to a composite material made of cellulose networks of fibrils imprinted by the plant at the nanoscale, which reinforces a soft wall polysaccharide matrix. The inversion of the handedness is explained using computational simulations considering filaments that contract and expand asymmetrically. The awns of Erodium are known to present hygroscopic movements, forming R helices in the dry state, but the possibility of actuating chirality via humidity suggests that these cellulose-based skeletons, which do not require complicated lithography and intricate deposition techniques, provide a diverse range of applications from intelligent textiles to micro-machines.