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Humidity sensors based on flexible sensitive nanomaterials are very attractive in noncontact healthcare monitoring. However, the existing humidity sensors have some shortcomings such as limited sensitivity, narrow relative humidity (RH) range, and a complex process. Herein, we show that a tin sulphide (SnS) nanoflakes-based sensor presents high humidity sensing behaviour both in rigid and flexible substrate. The sensing mechanism based on the Schottky nature of a SnS-metal contact endows the asfabricated sensor with a high response of 2491000% towards a wide RH range from 3% RH to 99% RH. The response and recovery time of the sensor are 6 s and 4 s, respectively. Besides, the flexible SnS nanoflakes-based humidity sensor with a polyimide substrate can be well attached to the skin and exhibits stable humidity sensing performance in the natural flat state and under bending loading. Moreover, the first-principles analysis is performed to prove the high specificity of SnS to the moisture (H 2 O) in the air. Benefiting from its promising advantages, we explore some application of the SnS nanoflakes-based sensors in detection of breathing patterns and non-contact finger tips sensing behaviour. The sensor can monitor the respiration pattern of a human being accurately, and recognize the movement of the fingertip speedily. This novel humidity sensor shows great promising application in physiological and physical monitoring, portable diagnosis system, and noncontact interface localization.

Nucleobases detection is important in DNA sequencing, disease testing linked to genes, and disease treatment. In this work, the interactions of nonmetallic element (Si, P, Cl, Se) doped MoS2 monolayer and nucleobases (A, C, G, T, U) have been studied by first-principles based on density functional theory. Their optimal configurations, the corresponding adsorption energies, charge transfer, and electrical properties are calculated. The adsorption strength and charge transfers after doping Si and P are all larger than that of the pristine MoS2. And they are better at distinguishing nucleobases due to the large standard deviations (θ) of five adsorption energies from same substrate. For the Si–MoS2 monolayer, the nucleobases are perpendicular to its surface, with large charge transfer (0.25e to 0.36e) and adsorption energy (−3.16 to −2.43 eV). And the molecules have significant effects on the electrical properties of Si–MoS2, including band dispersion curve and band gap, due to orbital hybridization between the substrate and the molecules. These results show there’s chemical adsorption between them, which suggest that Si–MoS2 monolayer can be used as a potential probe platform to detect biomolecule. While physical adsorption occurs between P–MoS2 and nucleobases with moderate adsorption energy (−1.17 to −0.71 eV) and change transfer (0.13 to 0.34e). After absorbing single nucleobase molecule, the conductivity of P–MoS2 changes, which suggest its distinguishability and sensitivity to these molecules. And the predicted recovery times of A, C, G, T and U are 300 ms, 9 s, 49 s, 5 ms, and 0.09 ms at 400 K, respectively, which indicate that P–MoS2 monolayer has a potential application prospect in DNA/RNA sequencing.

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