New robotic devices will benefit from new materials capable of controllable and variable material properties. In this thesis, we present a new composite laminated material with periodically arranged patterns of stiff and soft regions, laminated together in a multi-layer configuration with a central sliding layer, which is called sliding-layer laminates (SLLs). We first build a model based on Euler-Bernoulli beam theory and compute the stiffness variation as a function of layer alignment; we then explore the design principles, manipulating the stiffness patterning on the SLLs using computational and experimental methods. The comparison theory and experiment for two design principles exhibited strong agreement with differences only in the soft SLLs. In experiment, we demonstrate an up to 6-7 folds stiffness variation based on the fixed end cantilever beam test and an infinite stiffness variation is observed from the theoretical model. The effective bending stiffness under different sliding positions of the central laminate varies continuously with sufficiently many intermediate stiffness states available. To demonstrate the applicability of SLLs for robot locomotion, we implemented our SLL as a variable compliance wing structure in a wind tunnel and a robotic fish tail in a water tank to observe both the fluttering (air flow) and flapping motions (water flow) under actively tunable stiffness. The result shows great changes in amplitude (wing tip) and force (tail body) generations which indicates strong applications for multi-functional material to be exploited in mobile robots to achieve high performance under changing working conditions. In the future we envision, that SLL can be further extended into multiple areas, including innovative fabrication methods, multi-convertible properties, and high-dimensioned structures which will promote low-cost, easy controlled variable compliance solution into more unknown fields. Representative of a whole type of smart materials with tunable physical properties, the development of the SLL is still in its infancy, and the future applications of such an integrated multi-functionality system can be broadly extended in assisting the construction of bio-inspired Robotics
