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Evaluating sleep quality through monitoring sleep state is crucial for improving the general public’s sleep health. This article proposes a sleep state monitoring system based on flexible pressure sensor arrays, hardware circuits, and intelligent algorithms, which can effectively evaluate sleep quality by monitoring sleeping posture and breathing state. A flexible capacitive pressure sensor array designed specifically for monitoring sleeping posture, which is based on a dust-free cloth substrate and a sponge dielectric layer with multiple layers of microstructure, manufactured using electrospinning technology. In addition, we have developed a three-layer core-shell linear fiber structure flexible capacitive sensor for monitoring breathing state based on wet spinning technology. These soft and biocompatible wearable sensor arrays are connected to signal acquisition circuits, which can wirelessly transmit data on sleeping posture and breathing state to the PC in real time for efficient monitoring. We also constructed a model based on multiclassification support vector machine (SVM) to recognize four sleeping postures, including supine state, prone state, left lying, and right lying, with an accuracy rate of up to 96%. Finally, a comprehensive analysis of sleeping posture and breathing state can provide a comprehensive evaluation of sleep quality and targeted sleep improvement suggestions based on monitoring results. The designed sleep state monitoring system can not only provide long-term sleep data for medical professionals but also provide important information for the diagnosis of patients with sleep disorders.

Bionics has given a new impetus to the development of flexible sensors. This article shows the scheme of designing flexible resistance pressure sensor with high performance by using multilevel microstructure on the surface of natural hosta leaf. A conductive network composed of multiwalled carbon nanotubes (MWNTs) was formed on the surface of leaves by spraying method, and the piezoresistive layer was fabricated by coating polydimethylsiloxane (PDMS) to replicate multilevel microstructure. The biomimetic multilevel microstructure formed by placing the leaf veins of two piezoresistive layers in a special intersecting “#” shape ensures the stability and high sensing performance of the designed sensor, such as high sensitivity of 1.619 kPa $^{-{1}}$ , wide pressure detection range (>100 kPa), fast response time, low detection limit, and high stability. The sensor shows its practical application in human joint motion, micro-vibration detection, and tactile feedback for robot grasping, which are potentially useful in wearable devices and intelligent prosthetics.

Flexible sensor technology has a great significance in fields, such as human joint motion signal detection. We proposed a flexible detachable capacitive sensor based on nonparallel electrodes fixed on the inner side of the finger joint. The sensing unit was composed of copper electrode, barium titanate (BaTiO3)/polydimethylsiloxane (PDMS) film, and polyimide (PI) tape. The relative area and distance of the electrodes and the relative dielectric constant of the dielectric layer were changed with the rotation of the finger joint. A theoretical model of the sensor was established, and the function relationship between capacitance and finger joint bending angle was reflected. The sensor improved the previous problems of hysteresis and lack of stability caused by uneven force, unsecure install, and material viscoelasticity when the sensor was directly attached to the measured finger joint. The results indicate that the sensor has potential application value in fields, such as sports rehabilitation and joint disease assessment.

Flexible pressure sensors have advantages in human walking feature recognition because of their good flexibility and sensitivity. In this article, a flexible pressure sensor with stable mechanical properties and high sensitivity was designed based on the single-layer interdigital electrode made by the screen-printing process and the piezoresistive layer with a pyramidal microstructure made by the double inversion method. This structural design improves the sensitivity and wear resistance of the flexible pressure sensor and reduces the difficulty of packaging. The prepared flexible pressure sensor shows a higher sensitivity (−0.886 kPa $^{-{1}}$ ), a wider measurement range (0–180 kPa), a faster response time (80 ms), a lower detection pressure (11.8 Pa), and excellent durability. Then, a human plantar pressure monitoring system based on the flexible pressure sensor array was constructed to reflect the changes in human plantar pressure. Also, this monitoring system can recognize five types of human walking features through the support vector machine (SVM) algorithm. This work proves that the prepared flexible pressure sensor can be used as a flexible wearable device to accomplish complex tasks, such as recognizing human walking features, and it shows great potential in the field of health diagnosis.

As an essential component in wearable electronic devices and intelligent robots, flexible pressure sensors have enormous application value in fields such as healthcare, human–computer interaction, and intelligent perception. However, due to the complex and ever-changing pressure loads borne by sensors in different application scenarios, this also puts great demands on the flexible response and adjustment ability of a sensor’s detection range. Therefore, developing a flexible pressure sensor with a wide and adjustable detection range, which can be applied flexibly under different pressure loads, is also a major challenge in current research. In this paper, we propose a flexible pressure sensor with a wide and adjustable detection range based on an inflatable adjustable safety airbag as the dielectric layer. This sensor uses inflatable airbags prepared using 3D printing technology and silicone reverse molding technology as the dielectric layer and achieves high sensitivity (0.6 kPa–1to 1.19 kPa–1), wide detection range (220–1500 kPa), and flexible performance applicability by adjusting the air pressure inside the dielectric layer. At the same time, its simple production process, convenient production, fast response time (100 ms), and good stability provide the possibility for the flexible application of sensors in different pressure detection. The experimental results indicate that the sensor has enormous potential for applications in wearable devices, healthcare, human–computer interaction, and intelligent perception recognition.