Highly sensitive and flexible pressure sensor based on two-dimensional MoSe2 nanosheets for online wrist pulse monitoring.

The advancement of portable and flexible electronics that is integrated with multiple sensing functions has increasingly drawn considerable interest. The fabricated sensors would have the ability to sense multiple deformations like pressing, twisting and trivial vibrations such as pulses of wrist vibrations to mimic human skin. Presently, we implemented an easy, cost-effective and optimized fabrication technique for production of pressure sensors based on MoSe2 nanosheets coated on cellulose paper. The present sensor exhibits an incorporation of large pressure sensitivity of 18.42 kPa-1 in pressure range 0.001-0.5 kPa, 7.28 kPa-1 in pressure range 1-35 kPa and 2.63 kPa-1 in pressure range 40-100 kPa, working in broad pressure range (from 0.001 to 100 kPa) and long-term stability up to 200 deformation cycles at 2 kPa. The sensor showed excellent response towards the detection of vibrations of machines including cellular phone, compressor, etc. Besides, the sensor shows excellent environmental stability and exhibits immune piezo-resistive response to temperature variation.

Flexible paper based piezo-resistive sensor functionalised by 2D-WSe2 nanosheets.

High-performance electronics demand extremely sensitive piezo-resistive sensors with important features such as low-fabrication cost, easy implementation, low power consumption and high-pressure sensitivity over broad pressure range. Herein, we report a flexible piezo-resistive paper-based device functionalised by WSe2 nanosheets. An efficient and low-cost fabrication strategy using Whatman filter paper and tissue paper is adopted for versatile sensing applications. The WSe2 nanosheets were synthesized by high-yield and size-controlled liquid phase exfoliation technique. The flexible WSe2 nanosheets-paper sensor shows excellent response in broad pressure range of 1 Pa-100 kPa with exceptionally high sensitivity of 29.24 kPa-1, current responsivity of 70 and response time of 100 ms. The pressure sensor is also employed to recognize the pressure generated due to finger tapping. Encouragingly, the piezo-resistive sensors can also sense extremely small pressure differences of about 1.4 Pa generated by water drops.