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(Color online) A depiction of an antenna that reconfigures its shape in response to pressure (not to scale). (a) Empty microchannels with inlet holes (not shown in remaining depictions) (b) Rows of posts separate the two outermost segments of the antenna from the two innermost segments. (c) Injecting liquid metal into the microfluidic channels produces four antenna segments. Initially, the two innermost liquid segments of length L1 define the dipole antenna. The metal will not flow through the posts until the applied pressure exceeds the critical pressure required to yield the skin that mechanically stabilizes the liquid. (d) The four sections of metal merge into two longer sections (each of length, L2), which lowers the resonant frequency.
Photographs of a frequency shifting antenna in three different states. Length L1 is 12.6 mm. (a) State 1 consists of four isolated segments of liquid metal embedded in elastomer. The two innermost segments, L1:L1, define the antenna. Applying pressure to the right side of the antenna causes two of the sections to merge such that the dipole assumes a different geometry, state 2 (L1:L2). Merging both outermost segments with the innermost segments forms state 3 (L2:L2); (b) Micrographs of the region between the segments of metal. (i) A narrow gap defined by two rows of posts initially separates the segments. (ii) By applying sufficient pressure at the inlet, the metal flows between the posts and merges into an electrically continuous segment.
(Color online) Three distinct frequency responses illustrating the frequency shifting properties of the antenna. Measured spectra (open symbols) match well with the simulated spectra (filled symbols). As the arms of the antenna get longer (going from states 1 to 2 to 3), the spectral response of the antenna shifts to a lower resonant frequency.
(Color online) Sequential micrographs of the process of merging liquid metal segments. Images are taken from a high speed video camera and each frame represents about 0.3 ms. Pressure applied to the lower segment causes the liquid metal to rupture through two posts and merge with the adjacent metal to form an electrically continuous wire segment and thereby elongate the antenna.
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