  An electrically tunable terahertz (THz) plasmonic device is designed and
fabricated using liquid metals (eutectic gallium indium EGaIn) and shape memory
alloy wires (Flexinol). The liquid metal is injected into the voids of a
poly(dimethyl) siloxane (PDMS) microfluidic mold forming a periodic array of
subwavelength apertures, while the wires are inserted into the elastomer below
the metal plane. When a DC voltage is applied to the wires, they contract via
Joule heating, reducing the aperture periodicity and blue-shifting the
transmission resonances of the device. When the voltage is removed, the wires
cool and elongate back to their original length, allowing the transmission
spectrum to return to its original state. The magnitude of this change depends
upon the applied voltage. The device is shown to thermally cycle between the
relaxed state and the fully contracted state reproducibly over at least 500
thermal cycles. The asymmetric geometry of the device and the contraction
process yield transmission properties that are unexpected: two closely spaced
resonances, where both resonances correspond to the same scattering indices,
and an increase in the transmission amplitude of the lowest order resonance
upon contraction. We use numerical simulations to understand these features.
