  In this work, we study the thermo-mechanical behavior of metallic structures
designed to significantly change shape in response to thermal stimuli. This
behavior is achieved by arranging two metals with different coefficient of
thermal expansion (CTE), Aluminum and Titanium, as to create
displacement-amplifying units that can expand uniaxially. In particular, our
design comprises a low-CTE bar surrounded by a high-CTE frame that features
flexure hinges and thicker links. When the temperature increases, the
longitudinal expansion of the high-CTE portion is geometrically constrained by
the low-CTE bar, resulting in a large tangential displacement. Our design is
guided by theoretical models and numerical simulations. We validate our
approach by fabricating and characterizing individual units, one dimensional
arrays and three-dimensional structures. Our work shows that structurally
robust metallic structures can be designed for large shape changes. The results
also demonstrate how harsh environmental conditions (e.g., the extreme
temperature swings that are characteristic of extraterrestrial environments)
can be leveraged to produce function in a fully passive way.
