Autonomous Stretchable Sensor Array with Low-Power Wireless Readout for Spatial pH Mapping

• Stretchable 4 × 4 IrOₓ pH array with super-Nernstian (∼71 mV/pH) sensitivity • Integrated Zn-ion battery and BLE readout for autonomous wireless operation • PDMS-sealed Ag–PDMS vias enable stable pH sensing under prolonged strain • Real-time, high-density pH mapping demonstrated on tissue and food samples Spatial pH mapping on soft and deformable surfaces is important for applications such as wound healing assessment and food freshness mapping. However, conventional rigid pH sensors have limited use in these fields due to poor mechanical compliance, inadequate spatial resolution, and the need for wired power supplies. Here, we present an autonomous stretchable sensor array based on iridium oxide (IrO x ), powered by a low-power wireless multiplexed readout and a flexible zinc-ion battery, for 4 × 4 spatial pH sensing. These microstructurally optimised IrO x sensors exhibit a narrow super-Nernstian sensitivity of 71.25–72.69 mV/pH, with a drift below 0.01 pH/hour and robust performance after 100 stretchable cycles. The bespoke circuit employs a gain-optimised, low-noise analogue front-end with 16-channel acquisition, achieving near full-scale Analog-to-Digital Converter (ADC) utilisation (1 mV resolution) and sensitivity deviations below 1% when operated in ultra-low-power mode for wireless readout. The flexible zinc-ion battery integrates seamlessly with the circuits, providing sufficient operating time for the intended applications, and offering higher safety and biocompatibility than conventional lithium-based systems. This platform was validated on chicken and fish tissues at different stages of degradation and under mechanical strain, demonstrating strain-induced deviations below 0.02 pH. The proposed platform offers a reliable, mechanically compatible and fully integrated solution for real-time conformal biochemical mapping in clinical, environmental and food quality applications.