A horn antenna with circular aperture is proposed and designed based on the variation of the attenuation amplitude and the attenuation of electromagnetic wave in pipeline in the present paper. The simulation and tests show that the gain of the antenna is 15 dB and the return loss is À12.5 dB. The simulation and experimental results of simulated pipeline water cut test also show that the antenna was used to measure the water content in the range of 0%-100% of the water and oil in the pipeline. The water cut measurement of water and oil is less affected by the mixing type of oil-water mixture in the pipeline, because the main lobe of the antenna is located in the pipeline and the antenna has good directivity. The design of antenna in microwave sensor is useful for the field-testing and fundamental research.

High-performance artificial muscles have been received extensive attention from engineers and scientists in next-generation alternative bionic microelectronics and artificial intelligence operations. The response of smart materials under various external stimuli, such as electrical or magnetic fields, [1] heat, [2] solvents, [3] and the lights, [4] has been investigated. Most of them are based on materials such as dielectric elastomers, bilayer hydrogels, and liquid-crystal elastomers. Among the several types of soft actuators, flexible ionic polymer-metal composites (IPMCs) are regarded as promising candidates. Owing to their decent bending actuation at ultralow driving voltages (usually below 10 V), they have attracted considerable attention from researchers in the past 10 years. [5][6][7][8] The typical structure for IPMCs is composed of an ion-exchange membrane in the middle (e.g., commercial Nafion and Flemion membrane) and metal electrode layers (such as Pt and Ag) on both sides of the membrane. [9] The electrical actuation of IPMCs results from hydraulic and electrostatic effects. When the IPMCs were applied a voltage, the hydrated free counterions in the perfluorinated polymers can migrate to the oppositely charged electrodes. This immigration has caused bending of the actuator. [10] Meanwhile, the water molecules in the cathode area are ready to gather and swell while the anode area simply shrinks. [11] The inherent properties of this material have created a perfect option for different applications, such as soft robots, medical devices, bionic materials, and microelectromechanical systems. [12,13] It is known that the complexity and feasibility of IPMC-based actuators strongly depend on the driving voltage,

As an important index of industrial oil, moisture content affects the performance of oil. With the increase of requirement to the oil quality, the measurement of ultra‐low moisture content is gradually concerned. To achieve nondestructive measurement of the moisture content in oil, this paper analyzes the principle of dielectric loss of oil‐water mixture and proposes a measurement system based on the microwave transmission method. The hardware of the system, horn antenna, and experimental device were designed and built. The system uses a subtracter circuit together with a high‐performance microwave chip and high‐precision analog‐to‐digital converter to detect 1dB microwave attenuation. The results showed that the system can measure the moisture content of 0.01%–0.8% in quenching oil and the single detection absolute error is less than ±0.05%, and the average detection absolute error of 10 detections is less than ±0.02%. This study is useful for nondestructive detection of the moisture content in oil and provides a reference for related product development.