2D- SnS₂ Nanosheets Interspersed 3D-Hierarchical Melamine Foam-Based Ultra-Lightweight Composite for Multifunctional Sensing Applications

Flexible, lightweight, piezoresistive, scalable sensors with superior performance are of utmost importance in emerging wearable technologies. In this work, 2D- SnS₂ nanosheets interspersed 3D-melamine foam (MF) is used to develop a high-performance piezoresistive tactile and strain sensor. 2D- SnS₂ nanosheets are synthesized using the facile hydrothermal method and interspersed onto MF using the ultrasonic irradiation method. The ingenious usage of melamine foam provides a 3D hierarchical structure with excellent stretchability for the hybrid sensor and reduces the dependency on toxic, non-recyclable substrates, making the hybrid sensor eco-friendly. Detailed characterization studies reveal the formation of hexagonal phase SnS₂ nanosheets with uniform interspersion of nanosheets inside 3D-MS. The incorporation of SnS₂ improves the conductivity and sensitivity of the hybrid sensor, with reduced response/recovery time. The ultralight-weight hybrid sensor is used as a highly sensitive tactile sensor with a detection range from 0.5 – 80 kPa. Owing to the superior sensitivity of 0.1 kPa^-1, the tactile sensor is used as a finger-tip skin-inspired touch sensor and arterial pulse pressure sensor. Further, the fabricated SnS₂ nanosheets interspersed melamine foam when used as a strain sensor can detect compressive/tensile strain in the range of 0.5 – 60 %, with a gauge factor of 57 and also works as a large-area human motion monitoring system when integrated to body parts. The device displays an excellent response due to the synergistic properties like the excellent conductivity of 2D-SnS₂ and the macroporous nature of melamine foam. The fabricated device exhibits superior mechanical properties, scalability, sensitive responsiveness, and electromechanical durability for 5000 bending cycles making it a suitable candidate for various flexible and wearable applications. The material identification and facile fabrication strategy demonstrated in this work opens up new avenues for meeting the challenges in flexible electronic applications.