Tianyun Dong

In recent years, flexible 3-D force sensors have played a significant role in human–machine interaction due to their excellent compatibility with curved surfaces and multiaxis force detection capabilities. However, they generally suffer from inadequate sensitivity and severe signal coupling challenges. To address these limitations, this study introduces a flexible 3-D force sensor based on ionic capacitance, offering inherent signal decoupling and improved sensitivity. The sensor architecture utilizes polyvinyl chloride (PVC) gel as the dielectric medium, harnessing the electric doublelayer (EDL) effect, while ionic liquid doping is employed to enhance dielectric performance. Additionally, a vertically orthogonal electrode configuration enables efficient decoupling of 3-D force components. The sensor demonstrates outstanding performance, including high-directional sensitivity (5.80 N-1 normal, 2.39 N-1 tangential), fast dynamic response (response/recovery: 120/140 ms), and excellent durability (over 1200 cycles). The sensor is also capable of detecting forces as low as 0.1 N, indicating high resolution and responsiveness to subtle pressure changes. Finally, the sensor was successfully applied to the field of human–machine interaction applications including remote handle control, robotic grasping, and humanoid motion monitoring. The sensor’s high sensitivity and self-decoupling mechanism enable accurate detection of multiaxial force components, making it ideal for human–machine interfaces.

Flexible three-dimensional (3D) force sensors have received extensive attention from researchers due to their characteristics of being able to detect both normal forces and tangential forces. However, most current flexible 3D force sensors still use metal electrodes, which have posed challenges such as low bending and stretching properties, easy fracture, and larger mass. Herein, this paper proposed a fully flexible 3D force sensor utilizing liquid metal directly as the electrode to achieve full flexibility. Besides, a dielectric layer with a porous pyramid array structure was adopted to improve the properties of the sensor. The influence of the square and triangular electrode shapes on the performance of sensor was verified through theoretical deductions and experiments. The results show that the triangular electrode sensor exhibits higher sensitivity. The maximum sensitivity of the triangular sensor in the normal +Z direction is , and the maximum sensitivities in the tangential +X and +Y directions are and , respectively. Moreover, the sensor possesses rapid response performance (143ms), low hysteresis (3.61%), high resolution, small temperature and humidity drift, satisfactory dynamic stability, and long-term stability. Finally, the sensor was installed on a manipulator for object grasping, verifying its ability to detect 3D forces and its potential in non-destructive grasping.

Flexible sensors based on liquid metal (LM) fillers have attracted increasing attention due to their excellent stretchability, flexibility, and biocompatibility. However, simultaneously achieving transparency, high sensitivity, and robust mechanical performance remains a major challenge. In this study, we present a transparent and stretchable flexible composite sensor fabricated by combining poly(vinyl chloride) (PVC) with dibutyl adipate (DBA) and incorporating a low concentration (0.1 wt %) of LM as the conductive phase. The sensor exhibits a transparency of 50.12%, resulting from the optical clarity of the PVC/DBA matrix, the nanoscale dispersion of LM droplets, and the formation of Ga³⁺ ions upon partial surface oxidation, which collectively reduce light scattering and absorption. PVC also acts as a stabilizing matrix, forming a protective interface around LM droplets to enhance dispersion and interfacial stability. The resulting composite sensor demonstrates excellent stretchability (530%), high sensitivity (gauge factor = 4.27), and reliable performance in humid and saline environments. This work offers a practical strategy for developing transparent, durable, and high-performance composite sensors for wearable electronics and intelligent systems.

Flexible strain sensors based on fluid microchannels have been widely used in flexible electronics due to their excellent performance. However, the current research ignores the effect of different microchannel structures on the performance of flexible sensors, which is unsuitable for a specific practical application. Therefore, in this paper, sensors with microchannel of straight, wavy, and triangular structures were developed, and the performances of these sensors were compared from the results of simulation and experiment, respectively. The results show that the flexible strain sensors based on these three microchannels have extremely low hysteresis performance. Compared to the strain-stress hysteresis of the straight and wavy sensors, triangular sensors have the lowest hysteresis about 1.713%. Consistently, the triangular sensors also have the lowest hysteresis about 0.229% under strain–resistance response among these sensors. However, the straight sensors have the highest sensitivity among them. In different angles of the same microchannel group, the 180-degree wavy and 90-degree triangular sensors have the lowest hysteresis. Finally, the 90-degree triangular sensor was successfully used to detect the motion states of the human body and robotic finger. The research in this paper provides new ideas for choosing which microchannel of flexible strain sensors to be used in the field of wearable electronics.