Herein, we report the fabrication of a highly stretchable, transparent gas sensor based on silver nanowire-graphene hybrid nanostructures. Due to its superb mechanical and optical characteristics, the fabricated sensor demonstrates outstanding and stable performances even under extreme mechanical deformation (stable until 20% of strain). The integration of a Bluetooth system or an inductive antenna enables the wireless operation of the sensor. In addition, the mechanical robustness of the materials allows the device to be transferred onto various nonplanar substrates, including a watch, a bicycle light, and the leaves of live plants, thereby achieving next-generation sensing electronics for the 'Internet of Things' area.

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In wireless power transfer technology, power control technique is required to realise constant current (CC) and constant voltage (CV) modes for battery charging. CC and CV modes are needed to effectively charge lithium (Li)-ion batteries to ensure long life span and maximum capacity utilisation. The use of additional battery charging circuitry reduces efficiency, increases volume, and increases circuit complexity. The frequency modulation method is a method that can control power without an additional charging circuit, but a high-resolution controller is needed to control the voltage and current for charging the battery by frequency modulation. This study proposes a system that controls current and voltage for CC and CV modes through a step-charging method using a battery hysteresis with a low-cost control system. The in-band communication circuit is analysed and used to link the primary and secondary sides of the inductive power transfer (IPT) coils, which enables effective feedback control without an additional wireless communication module. This method enables high-efficiency charging while minimising the overall size and cost of mobile IPT applications such as power tools. The proposed system shows 90.3% transfer efficiency with a 20.75 V, 4 Ah Li-ion battery at 7 mm distance.

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