Low-Temperature Centimeter-Scale Growth of Layered 2D SnS for Piezoelectric Kirigami Devices.

Tin monosulfide (SnS) is a promising piezoelectric material with an intrinsically layered structure, making it attractive for self-powered wearable and stretchable devices. However, for practical application purposes, it is essential to improve the output and manufacturing compatibility of SnS-based piezoelectric devices by exploring their large-area synthesis principle. In this study, we report the chemical vapor deposition (CVD) growth of centimeter-scale two-dimensional (2D) SnS layers at temperatures as low as 200 °C, allowing compatibility with processing a range of polymeric substrates. The intrinsic piezoelectricity of 2D SnS layers directly grown on polyamides (PIs) was confirmed by piezoelectric force microscopy (PFM) phase maps and force-current corroborative measurements. Furthermore, the structural robustness of the centimeter-scale 2D SnS layers/PIs allowed for engraving complicated kirigami patterns on them. The kirigami-patterned 2D SnS layer devices exhibited intriguing strain-tolerant piezoelectricity, which was employed in detecting human body motions and generating photocurrents irrespective of strain rate variations. These results establish the great promise of 2D SnS layers for practically relevant large-scale device technologies with coupled electrical and mechanical properties.

Laser-assisted micropyramid patterned PDMS encapsulation of 1D tellurium nanowires on cellulose paper for highly sensitive strain sensor and its photodetection studies.

This work demonstrates the fabrication of tellurium-nanowires (Te-NWs)/paper based device encapsulated using laser assisted mircopyramid patterned polydimethylsiloxane (PDMS) films. Although there are multiple reports published on 1D Te, most of them are limited to establishing its properties and studying its behavior as a sensor and research on the utilization of Te-NWs for physical sensors remain unexplored. Further, reports on p-type photodetectors also remain scarce. The fabricated Te-NWs/paper with micropyramid structured PDMS films encapsulation was used as a strain sensor, and it exhibited considerable improvement (∼60%) in sensitivity compared to smooth PDMS films. The gauge factor of the developed strain sensor was found to be âˆ¼15.3. In addition, fabricated Te-NWs/paper device with contacts was used as a photodetector and it showed photoresponsivity of âˆ¼22.5 mA W-1and âˆ¼14.5 mA W-1in visible and NIR regions, respectively. Furthermore, the device exhibited long-term mechanical stability under harsh deformations. Fabricated 1D Te-NWs/paper device was utilized as a strain sensor to monitor the angular movements in the human body and successfully monitored various human motions, including wrist bending, finger knuckle, elbow joint, and knee joint. The successful demonstration of Te-NWs based physical sensors and utilization in broadband photodetectors opens avenues of research for tellurium based flexible and wearable devices.

A remarkably ultra-sensitive large area matrix of MXene based multifunctional physical sensors (pressure, strain, and temperature) for mimicking human skin.

Electronic skin has attracted a lot of interest in recent years due to its ability to mimic human skin and also its excellent conformability. Even though there are reports on electronic skin, the major issue that still needs to be resolved is achieving multifunctional sensing at the same time as ultra-high sensitivity. Hence, there is an immediate requirement to develop inexpensive, highly sensitive, and superior performance piezoresistive multifunctional sensors that mimic skin. Herein, an as synthesized pure MXene (Ti3C2Tx) colloidal solution was used to deposit a thin film on flexible polyurethane foam, forming a three-dimensional conductive network with an ultra-high sensitivity of ∼34.24 kPa-1 (1.477-3.185 kPa of applied pressure range) and an elevated gauge factor of ∼323.59 (5-20% of applied strain range). Further merits such as reproducibility, low cost, high scalability, and excellent stability after 2500 cycles imply the sturdiness of the fabricated device. The remarkable sensing efficiency can be attributed to the strong interaction of Ti3C2Tx and PU foam, the inherent 3D network of PU coupled with the excellent electrical properties of Ti3C2Tx, and the interconnection of the unconnected branches present in the internal framework of PU-foam, which indicates the existence of more conduction paths. Besides, the fabricated Ti3C2Tx was deposited on cellulose paper to be utilized as a temperature sensor which displayed ∼2.22 × 10-3 °C-1 TCR and 29.43 meV activation energy. Lastly, real time applications for the fabricated device are investigated including detecting an unknown position of an object and human gestures. The successful demonstration of the low-cost, flexible Ti3C2Tx based piezoresistive sensor has shown innovative applications in biomedical, security, educational, and health sectors.