Compliant mechanisms that achieve binary stiffness along multiple degrees of freedom

Here we introduce compliant mechanisms that can be triggered using bistable switches to achieve two different states of stiffness (i.e., high and low stiffness) along multiple degrees of freedom The compliant mechanisms leverage principles of constraint manipulation and stiffness cancelation to achieve these binary states with a stiffness difference as large as an order of magnitude. Although these principles have been used in prior works to achieve binary stiffness in compliant mechanisms that achieve a single degree of freedom (DOF) (e.g., a single translation or a single rotation), this work advances the theory to achieve binary stiffness in compliant mechanisms that achieve multiple DOFs. Specifically, two designs are introduced, fabricated, and tested to demonstrate binary stiffness in two DOFs. The first design achieves binary stiffness along two orthogonal translational DOFs and the second design achieves binary stiffness about two orthogonal rotational DOFs with intersecting axes.