With the development of the Internet of Things and information technology, a large number of inexpensive sensors are needed to monitor the state of the object. A wide variety of sensors with a low cost can be made using the difference in charge attractiveness between flexible polymers and other materials. Compared to the two solid materials, a sensor made of a solid polymer-liquid has a large contact area and low friction. A motion-balanced sensor is presented based on the polytetrafluoroethene pipe and nano-iron suspension. The effect of the concentration and volume of the nano-iron suspension on the output voltage of the sensor is analyzed. The motion-balanced sensor can be used to measure the tilt angle of the object and there is a linear relationship between the output voltage and the tilt angle. A comparison test is performed to a commercial acceleration sensor with PZT-5. The test results show that the frequency characteristics and amplitude characteristics of the motion-balanced sensor are consistent with those of the acceleration sensor. The motion-balanced sensor can be used to determine the state of exercise such as walking, running, etc. The motion-balanced sensor has broad application prospects for monitoring the bridges and power towers balance, stroke patients’ health assessment, etc.

Three-dimensional tactile sensing in smart devices is witnessing an increasing demand. In this study, a three-dimensional tactile sensor is proposed according to the principle of triboelectricity by using polydimethylsiloxane (PDMS) and polyethylene oxide (PEO) films. Use of PDMS-ZnO composite films increases the output voltage of the electrodes. The sensor is designed with a cross beam-shaped pressure head to enable sensing normal forces in five directions. The working mechanism of the sensor is analyzed using the finite element method. The calculation results indicate a linear relationship between the output voltage and the force. The simulation results also demonstrate that the output voltage is linearly correlated with the applied force in the range of 1-30 N. Test results show that the sensor can sense the magnitude, frequency, and direction of the force as well as measure the duration of the force. The hardness of the object has a significant effect on the output voltage. Finally, the sensor is tested on a manipulator grasping an object to demonstrate its ability to sense the contact and sliding of the object.

Rotation detection is widely applied in industries. The current commonly used rotation detection system adopts a split structure, which requires stringent installation requirements and is difficult to miniaturize. This paper proposes a single-piece self-powered non-contact sensor with an interdigital sensitive layer to detect the rotation of objects. The electric field generated between a polyurethane (PU) film and a polytetrafluoroethylene (PTFE) film is utilized for perceiving the rotation. The surface of the PU film is subjected to wet etching with sulfuric acid to increase the surface area and charge density. Through finite element analysis and experimental testing, the effects of the areas of the sensitive films as well as the horizontal and vertical distances between them on the output voltage are analyzed. Tests are performed on adjustable-speed motors, human arms, and robotic arms. The results show that the sensor can detect the speed, the transient process of rotation, and the swing angle. The proposed rotation sensor has broad application prospects in the fields of mechanical automation, robotics, and Internet of Things (IoT).