Synthesis of large-area patterned MoS 2 is considered the principle base for realizing high-performance MoS 2 -based flexible electronic devices. Patterning and transferring MoS 2 films to target flexible substrates, however, require conventional multi-step photolithography patterning and transferring process, despite tremendous progress in the facilitation of practical applications. Herein, an approach to directly synthesize large-scale MoS 2 patterns that combines inkjet printing and thermal annealing is reported. An optimal precursor ink is prepared that can deposit arbitrary patterns on polyimide films. By introducing a gas atmosphere of argon/hydrogen (Ar/H 2 ), thermal treatment at 350 °C enables an in situ decomposition and crystallization in the patterned precursors and, consequently, results in the formation of MoS 2 . Without complicated processes, patterned MoS 2 is obtained directly on polymer substrate, exhibiting superior mechanical flexibility and durability (≈2% variation in resistance over 10,000 bending cycles), as well as excellent chemical stability, which is attributed to the generated continuous and thin microstructures, as well as their strong adhesion with the substrate. As a step further, this approach is employed to manufacture various flexible sensing devices that are insensitive to body motions and moisture, including temperature sensors and biopotential sensing systems for real-time, continuously monitoring skin temperature, electrocardiography, and electromyography signals.

Flexible and wearable pressure sensors attached to human skin are effective and convenient in accurate and real-time tracking of various physiological signals for disease diagnosis and health assessment. Conventional flexible pressure sensors are constructed using compressible dielectric or conductive layers, which are electrically sensitive to external mechanical stimulation. However, saturated deformation under large compression significantly restrains the detection range and sensitivity of such sensors. Here, we report a novel type of flexible pressure sensor to overcome the compression saturation of the sensing layer by soft-strain effect, enabling an ultra-high sensitivity of ~636 kPa −1 and a wide detection range from 0.1 kPa to 56 kPa. In addition, the cyclic loading-unloading test reveals the excellent stability of the sensor, which maintains its signal detection after 10,000 cycles of 10 kPa compression. The sensor is capable of monitoring arterial pulse waves from both deep tissue and distal parts, such as digital arteries and dorsal pedal arteries, which can be used for blood pressure estimation by pulse transit time at the same artery branch.

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Pressure sensors are considered the key technology for potential applications in real-time health monitoring, artificial electronic skins, and human− machine interfaces. Despite the significant progress in developing novel sensitive materials and constructing unique sensor structures, it remains challenging to fabricate large-area pressure sensor arrays due to the involvement of complex procedures including photolithography, laser writing, or coating. Herein, a scalable manufacturing approach for the realization of pressure sensor arrays with substantially enlarged sensitive areas is proposed using a versatile screen-printing technique. A compensation mechanism is introduced into the printing process to ensure the precise alignment of conductive electrodes, insulation layers, and sensitive microstructures with an alignment error of less than 4 μm. The fully screen-printed sensors exhibit excellent collective sensing performance, such as a reasonable pressure sensitivity of −2.2 kPa −1 , a fast response time of 40 ms, and superior durability over 3000 consecutive pressures. Additionally, an integrated 16 × 32 pressure sensor array with a sensing area of 190 × 380 mm 2 is demonstrated to precisely recognize the sitting postures and the body weights, showing great potential in continuous and real-time health status monitoring.