The stress created by the austenite transformation of mechanically constrained NiTi shape memory alloys (SMAs) significantly exceeds that required to deform (detwin) its low temperature martensitic phase. The one-way shape memory effect can therefore be used to create antagonistic, fully reversible flexural shape morphing structures by assembling opposing pairs of linear contractile SMA actuators. These structures possess two distinct inactive configurations, neither of which requires continuous power for shape retention making them potentially suitable for long-term applications. Here, the shape changes of a representative antagonistic flexural unit cell have been experimentally evaluated, and the effect of the pre-strain of near equiatomic NiTi alloys on the actuation strain has been analyzed and discussed. The predicted deformations are then successfully compared to the response of prototype actuators.

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Lightweight structures capable of changing their shape on demand are of interest for a number of applications, including aerospace, power generation, and undersea vehicles. This paper describes a bioinspired cellular metal vertebrate structure which relies on shape memory alloy (SMA) faces to achieve fully reversing shape change. The resulting vertebrate actuators can be combined with flexible face sheets to create a load-bearing, shape morphing panel. Performance of the vertebrate actuator in terms of maximum curvature and moment is analyzed and discussed. A recently constructed, prototype shape morphing airfoil is used to illustrate the concept.

Heteroepitaxial growth of Si(0.7)Ge(0.3)/Si(001) films under kinetically limited conditions leads to self-assembly of fourfold quantum dot molecules. These structures obtain a narrowly selected maximum size, independent of film thickness or annealing time. Size selection arises from efficient adatom trapping inside the central pit of the quantum dot molecule when the surrounding islands cojoin to form a continuous wall. Self-limiting growth of nanostructures has significant implications for novel nanoelectronic device architectures such as quantum cellular automata.

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