Recently, wearable and flexible pressure sensors have sparked tremendous research interest, and considerable applications including human activity monitoring, biomedical research, and artificial intelligence interaction are reported. However, the large-scale preparation of low-cost, high-sensitivity piezoresistive sensors still face huge challenges. Inspired by the specific structures and excellent metal conductivity of a family of two-dimensional (2D) transition-metal carbides and nitrides (MXene) and the high-performance sensing effect of human skin including randomly distributed microstructural receptors, we fabricate a highly sensitive MXene-based piezoresistive sensor with bioinspired microspinous microstructures formed by a simple abrasive paper stencil printing process. The obtained piezoresistive sensor shows high sensitivity (151.4 kPa −1 ), relatively short response time (<130 ms), subtle pressure detection limit of 4.4 Pa, and excellent cycle stability over 10,000 cycles. The mechanism of the high sensitivity of the sensor is dynamically revealed from the structural perspective by means of in situ electron microscopy experiment and finite element simulation. Bioinspired microspinous microstructures can effectively improve the sensitivity of the pressure sensor and the limit of the detectable subtle pressure. In practice, the sensor shows great performance in monitoring human physiological signals, detecting quantitatively pressure distributions, and remote monitoring of intelligent robot motion in real time.

can effectively capture subtle changes of pressures is much needed. To date, plenty of pressure sensors have been explored, including capacitive, [2,3] piezoelectrical, [4][5][6] and piezoresistive [7,8] pressure sensors. Among them, piezoresistive sensors stand out as promising candidates due to their low-cost fabrication, stability to temperature, sensitivity to pressure, etc. Piezoresistive pressure sensors can transduce changes of mechanical strain into changes of electrical resistance, and are broadly used due to their simple work mechanism and sensitivity to pressure. [9] Conventional piezoresistive pressure sensors, however, are usually based on rigid substrates like Si, [10] which are not skin-mountable and cannot meet the needs for portability and flexibility of smart wearable electronic devices. To tackle this problem, one possible way is the combination of flexible insulating matrices with carbonaceous nanomaterials as conductive fillers, such as graphene, [11] reduced graphene oxide (rGO), [12] and carbon nanotubes (CNTs). [13] For example, Park et al. combined wrinkled CNT and PDMS to build a pressure sensor [14] and more recently, Pang et al. prepared a pressure sensor based on rGO and micro-patterned PDMS substrate. [15] However, composite flexible pressure sensors like these often suffer from a performance compromise between sensor sensitivity and linear region. [16] Apart from that, the signal stability of the sensor may be influenced by the thermal expansion of the polymer substrate. [9] Another way is the utilization of the carbonaceous nanomaterials as the building blocks for making highly elastic materials. In particular, carbon aerogels prepared by this method have demonstrated extraordinary mechanical properties, [17] good flexibility, [18] high aspect ratio, [19] and exceptional thermal stability. [20] Over the past few years, a considerable amount of reports have focused on piezoresistive pressure sensors based on reduced graphene oxide (rGO) aerogel or rGO composite aerogel. For instance, Ha et al. prepared a PAA/ rGO composite aerogel for pressure sensing, [21] and recently, Peng et al. made a piezoresistive sensor based on CNT/rGO-CNF aerogel. [22] However, it still remains a challenge to further improve the sensitivity and the detecting range of these carbon aerogel based pressure sensors.Recently, a new kind of 2D transitional metal carbide/carbonitride materials (MXenes) with metal conductivity have Pressure sensing is key to smart wearable electronics and human-machine interaction interfaces. To achieve a high-performance pressure sensor that has broad linear range and is capable of detecting subtle changes of pressure, the good choice of sensing materials and rational design of structures are both needed. A novel piezoresistive sensor based on hollow MXene spheres/ reduced graphene composite aerogel and flexible interdigital electrodes is presented. Benefiting from the unique microstructure of the composite aerogel, the prepared pressure sensor exhibits high sensitivity (609 kPa −...

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