Guoxiao Yin

Plasticized polyvinyl chloride (PVC) gel is a mechanically compliant soft material with potential for flexible mechanoelectrical sensing. However, many PVC-gel-based sensors rely on conductive fillers, ionic additives, or specially designed conductive pathways, which increase material complexity and may introduce concerns related to filler dispersion, leakage, interfacial instability, and long-term signal drift. Here, we report a surface-structured, filler-free PVC gel sensor capable of producing self-generated mechanoelectrical signals under mechanical compression. The PVC gel was prepared by solution casting and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, x-ray diffraction, thermogravimetric–differential scanning calorimetry, mechanical testing, dynamic mechanical analysis (DMA), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Among the investigated surface architectures, the conical array delivered the strongest low-pressure response, with a nominal-pressure sensitivity of 110.59 Mv kPa ⁻¹ over 0.0356–0.1422 kPa, approximately 23.5-fold higher than that of the structureless control. The sensor was experimentally evaluated over 0.0356–0.7111 kPa and exhibited response and recovery times of approximately 500 and 300 ms, respectively. The enhanced response is interpreted through the combined effects of a low apparent secant modulus, amplified deformation, pressure-dependent real contact-area modulation, and interfacial charge redistribution within a proposed phenomenological electric-double-layer-like interfacial framework. A simplified geometric analysis suggests that the conical structure provides the largest normalized contact-area modulation under weak compression. The rate-dependent response, DMA, electric-modulus analysis, EIS, and CV characterize the coupled time-dependent mechanical and electrical behavior and are consistent with this mechano-interfacial interpretation. The intermittent cyclic test indicates partial signal recovery while maintaining a stable waveform. A qualitative Morse-code demonstration produced distinguishable temporal signal patterns under manually applied dot–dash inputs. This work provides a compositionally simple, filler-free strategy for enhancing the low-pressure self-generated mechanoelectrical response of PVC gels.

This work presents the fabrication and a systematic evaluation of an ionic polymer-metal composite (IPMC) sensor, focusing on its potential for human motion monitoring and human–computer interaction. The sensor was fabricated via a solution casting and electroless plating process, and its morphology characterized using scanning electron microscopy. The sensing performance was comprehensively assessed, revealing high sensitivity (1.059 mV/N) in the low-pressure region, a fast response time (~50 ms), and reliable stability over prolonged cyclic testing. Furthermore, the sensor can respond to both the magnitude and rate of applied mechanical stimuli. To explore its application potential, the IPMC was tested in scenarios ranging from input pattern recognition—including distinguishing mouse-click patterns, handwritten letters, and binary-encoded presses—to human motion monitoring, where it effectively captured and differentiated signals from facial expressions, swallowing, breathing, and joint movements. The results suggest that the developed IPMC sensor is a promising candidate for applications in wearable health monitoring and flexible interactive systems.

Ionic polymer–metal composites (IPMCs) are a class of ionic electroactive smart materials, which can produce large deformation under low driving voltage. They have the advantages of light weight, good flexibility, and high energy density, and have broad application prospects in fields such as bionic actuators, soft robots, and flexible sensors. To achieve rapid fabrication and multi-degree-of-freedom (multi-DOF) motion of IPMCs, this study demonstrates, for the first time, the fabrication of a square rod-shaped IPMC actuator via fused deposition modeling 3D printing. The printed square rod-shaped IPMC actuator exhibits high dimensional accuracy and a distinct layer-by-layer structure. It also demonstrates excellent conductivity and high specific capacitance. Actuation tests confirm its capability for well-defined 2-DOF motion. Under a 4 V direct current (DC) voltage for 60 s, the square rod-shaped IPMC actuator achieved blocking forces of 163.7 mN ( x direction) and 177.9 mN ( y direction), with bending angles of 24° and 41° (in the x and y directions, respectively) under the same condition. Furthermore, it lifted a weight 70 times its own weight, with a power density of 112.49 W m ⁻³ . This work lays a solid foundation for the rapid prototyping and practical application of multi-DOF IPMC actuators.

In this work, a helical ionic polymer metal composite (IPMC) was fabricated by thermal treatment in a mold with helix grooves. The axial actuation behaviors of the helical IPMC actuator were observed, and the electromechanical and electrochemical characteristics were evaluated. The experimental results showed that as the voltage increased and the frequency decreased, the axial displacement, axial force, and electric current of the actuator all increased. Compared with square wave and sinusoidal signals, the actuator exhibited the most satisfactory motion under the direct current (DC) signal. For the electrochemical test, as the scanning rate decreased, the gravimetric specific capacitance increased. Within a suitable voltage range, the actuator was chemically stable. In addition, we coupled the Electrostatics module, Transport of Diluted Species module, and Solid Mechanics module in COMSOL Multiphysics software to model and analyze the helical IPMC actuator. The simulation data obtained were in good agreement with the experimental data. Finally, by using three helical IPMC actuators as driving components, an innovative three-degree-of-freedom (3-DOF) micro-parallel platform was designed, and it could realize a complex coupling movement of pitch, roll, and yaw under the action of an electric field. This platform is expected to be used in micro-assembly, flexible robots, and other fields.