Smart Bioinspired Material-Based Actuators: Current Challenges and Prospects

Abstract

This research review discusses several examples of plant movements, either depending on the direction of the triggering stimuli (tropisms) or not (nastic responses), which have served as inspiration to develop smart biomimetic actuators. In addition, it presents an overview of the multiple approaches for the development of autonomous actuators based on synthetic materials, as well as of their advantages and disadvantages, applicability, and limitations. The classification is based on structural and conformational characteristics (mono-, bi-, or multimaterial assemblies, their orientation, chemical structures, and geometrical configurations). Additionally, this review presents an alternative formulation and extension of the pioneering Timoshenko's model, which provides an understanding of the underlying mechanical principle of bilayer bending actuation. Finally, upscaled applications of this actuation principle are described, focusing mainly on biomimetic architecture. Attention is given to previously reported real-life applications based on bio-based materials and material systems. Furthermore, this review discusses the multiple challenges for synthetic materials when an upscaling perspective is intended. In this sense, key aspects such as time responsiveness and mechanical amplification, in terms of speed, displacement, and load-bearing capability, are discussed.