Researchers fabricate flexible antennas to be used in stimuli-responsive electronics

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North Carolina State University has taken its research on conductive liquid elements that can be used as antennas to a next level. Copper has been found unsuitable for flexible electronics due to its irreversible deformation at high strain. Scientists thereby have come up with a low-viscosity metal alloy, eutectic gallium indium that is placed in a 51mm long micro channel. The micro channel is divided into four segments with posts separating two outermost segments from two innermost ones. The liquid metal automatically forms an ‘oxide’ skin composed of gallium that prevents metal in adjacent segments from merging.

Shape-changing liquid metal antenna

Since the antennas are stretchable, their resonant frequency is changed by altering the shape of antenna. By making the antenna, longer frequency is changed to lower values and vice versa. The two inner segments of length 25mm serve as the shortest antenna with the highest frequency. Pressure is applied on the liquid metal to elongate the antenna and decrease the frequency. The second state is attained by applying a critical pressure that ruptures oxide skin and merges the metal between the posts with the one in outermost segments. The pressure is further increased to get the third state allowing liquid metal in outer and inner segments to merge.

The technology is expected to find application in different areas such as wireless sensing, health monitoring, switches, radio-frequency identification tags, and military applications. Many other reconfigurable antennas have been proposed before, but this one offers a simpler design. The current antenna does not require any mechanical or electrical switch. The response to stimuli as well as functions of antenna can be controlled and stimulated. Moreover, it is not reversible, i.e., it can only go from higher to lower frequency and not vice versa. Scientists are working to make further improvements to the antenna. According to them, flexing could also be used to merge the liquid metal with outer segments. It is only by using such different stimuli that the reversible switching can be made possible in the future.

Via: Physorg