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This article presents a dual‐band filtering power amplifier (DB‐FPA) with extended passband bandwidths and wide stopband rejection, which is helpful in reducing the number of microwave components in the dual‐band radio frequency front end, resulting in compact circuit size and low loss. In the designed DB‐FPA, a wideband low‐pass filter is applied as the input matching network (IMN) to provide wideband impedance matching and good stopband rejection, while a dual‐band filtering impedance transformation is adopted as the output matching network (OMN) to provide dual‐band impedance matchings and filtering responses simultaneously. Specifically, the IMN is constructed by high‐impedance transmission‐line sections and low‐impedance open‐circuit stubs. The OMN is designed based on the specific external quality factors and coupling coefficients during two bands, resulting in dual‐band impedance transformations and dual‐band filtering responses. Then, based on the above IMN and OMN, the design procedure of the presented DB‐FPA is summarised. To verify the proposed idea, a novel DB‐FPA has been fabricated and measured. During the two frequency bands, the measured maximum power added efficiencies are 55.11% and 47.78% within 33.0 dBm input power, while the measured peak gains are 15.4 and 14.0 dB within 15.0 dBm input power. [ABSTRACT FROM AUTHOR]

Liquid gates can provide an effective method to control the release of substances. However, the size of liquid gates and the control methods limit their broad applications. The controllable large deformation of liquid metals (LMs) makes it possible to be used in liquid gate design with simple actuation methods. Here an LM gate that can be easily driven under moderate conditions is proposed, on demand opening at mild electrical voltage (2–5 V) and closing at an oscillating mechanical force (≈0.05 N) in a wide range of pH (2–12). The gating mechanism relies on the large surface tension alteration at these conditions, which directly changes the shape of the LM from a flat film to a contracted meniscus to one side of the copper gate‐frame. As demonstrated, this gate can be applied to release substances such as liquid (ink), biomolecule (insulin) by free diffusion. Moreover, single‐channel and multichannel gates can be realized for high throughput control. The biocompatibility of the whole gate is also proved by cytotoxicity assays. Above all, a novel LM gate is offered with simple structure and easy control, which may bring inspiration to applications in controlled substance release and separation. [ABSTRACT FROM AUTHOR]