As an important branch of wearable electronics, flexible pressure sensors have attracted extensive research owing to their wide range of applications, such as human–machine interfaces and health monitoring. To fulfill the requirements for different applications, new material design and device fabrication strategies have been developed in order to manipulate the mechanical and electrical properties and enhance device performance. In this paper, the important progresses in flexible pressure sensor development over recent years are selectively reviewed from a material and application perspective. First, an overview of the fundamental working mechanism and the systematic design approach is presented. Particularly, how the theoretical modeling has been used as an auxiliary tool to achieve better sensing performance is discussed. A number of applications, including human–machine interfaces, electronic skin and health monitoring, and certain application‐driven functions, e.g., pressure distribution visualization and direction‐sensitive force detection, are highlighted. Lastly, various advanced manufacturing methods used for realizing large‐scale fabrication are introduced.

Natural wood possesses a unique 3D microstructure containing hierarchical interconnected channels along its growth direction. This study reports a facile processing strategy to utilize such structure to fabricate carbon/silicone composite based flexible pressure sensors. The unique contribution of the multichannel structure on the sensor performance is analyzed by comparing the pressure response of the vertically cut and horizontally cut composite structures. The results show that the horizontally cut composite based sensors exhibit much higher sensitivity (10.74 kPa ) and wider linear region (100 kPa, R = 99%), due to their rough surface and largely deformable microstructure. Besides, the sensors also show little hysteresis and good cycle stability. The overall outstanding sensing properties of the sensors allow for accurate continuous measurement of human pulse and respiration, benefiting the real-time health signal monitoring and disease diagnoses.

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Wearable pressure sensors enable long-term real-time health monitoring in a noninvasive and power-efficient way; however, the sensors are often required to be precisely applied at the optimal measurement spot, e.g., nearby radial artery, for signal acquisition, causing inconvenience for untrained users or the elders. In this paper, a wearable liquid-capsule sensor platform embedded with a piezo-resistive pressure sensor is presented for continuous, accurate, and alignment-relaxed physiological monitoring, i.e., heart rate (HR) and blood pressure (BP) tracking. The flexible capsule design ensures comfort and good device conformation to any skin regions. For HR and BP measurements, experiments are performed on 12 human subjects. The results show that the capsuled sensor can continuously track: 1) HR with a mean absolute difference (MAD) of 0.88 beats per minute (bpm) and 2) BP with a MAD<3 mmHg for both diastolic and systolic blood pressure. The new liquid-capsule-based sensor platform may help to realize an accurate, flexible, robust, and low-power solution for next-generation wearable health monitoring devices.

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