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(a) Overlay of SEM images showing a freestanding Ni-Mn-Ga double beam nanostructure (nanoactuator #1) after deformation (A) and after subsequent heating (B). (b) In-situ deflection of the beam tip during an electrical heating cycle and corresponding normalized electrical resistance of nanoactuator #1. The electrical resistance signal is interrupted between 1.1 and 1.95 mA due to experimental reasons. The length, width, and thickness of each nanobeam are 8 μm, 200 nm, and 250 nm, respectively.
Electrical resistance characteristics of a Ni-Mn-Ga double beam nanoactuator (#2) for a complete actuation cycle resulting in a hysteresis loop (black line) and for heating until destruction (bright red line). The inset shows a SEM image before actuation. The length, width and thickness of each nanobeam are 2 μm, 100 nm, and 125 nm, respectively.
(a) Coupled finite element simulation of temperature profiles along x-direction of Ni-Mn-Ga nanoactuator #2 for four different values of electrical heating current. The inset illustrates the geometry. The dashed line at x = 0 indicates the onset of the beam structure. (b) Simulation of normalized electrical resistance characteristics upon heating for the investigated Ni-Mn-Ga double beam actuators as indicated. The beam dimensions as well as the martensite phase fractions at the minima of electrical resistance characteristics are given.
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