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There is a need to develop low-cost and compact frequency reconfigurable antennas with continuous frequency tuning capability. Existing approaches rely on dedicated electrical, mechanical, or MEMS-based approaches to reconfigure the antenna, which requires extra components and fabrication steps. In this paper, we propose a physics-based approach to realize tunable helical antennas based on a shape memory alloy (SMA). By utilizing the temperature-induced irreversible mechanical deformation of the SMA, the temperature-controlled antenna can continuously change its resonant frequency and lock the state when the desired frequency response is achieved. The height of the helical antenna changes in response to applied temperatures. No additional circuitry or mechanical modules are required for the reconfiguration of the antenna geometry. The fabricated helical antenna can shift resonant frequency between 150 and 195 MHz with a tuning sensitivity of 284 kHz/°C. [ABSTRACT FROM AUTHOR]

Ionic liquid/ionogel gate dielectrics can provide significant advantages for transistor architectures that utilize high surface area semiconductors and/or nonplanar substrates because of their cleanroom-free, liquid-based processability and their inherently large electrostatic double layer capacitance. These attributes of ionogels have already enabled the facile fabrication of several up-and-coming transistor devices geometries for which a highly conformal interface between the electrolyte gate dielectric and the semiconductor is readily achievable, and remote gating with a nonaligned gate electrode is possible. Further, ionogel gating can improve device performance to maximize current densities at low operating voltages. This Perspective highlights three classes of emerging transistor architectures, namely, vertical transistors, surround gate transistors, and thread/fiber-based transistors, and provides several key examples of instances where ionogel gating has either already enabled or still stands to improve device fabrication and performance. [ABSTRACT FROM AUTHOR]