A 3D Nanomaterials‐Printed Wearable, Battery‐Free, Biocompatible, Flexible, and Wireless pH Sensor System for Real‐Time Health Monitoring

Abstract The pH sensing devices can provide important health information with applications in infection detection, disease diagnosis, and personalized medicine. However, these devices are often expensive with modest flexibility and require bulky readout instruments, thus inappropriate for wearable, remote, and continuous health monitoring applications. Herein, an integrated, miniaturized, modular, wearable, battery‐free, biocompatible, flexible, 3D‐printed (WB²F3D) sensor system for on‐demand, continuous, wireless, and real‐time pH monitoring is proposed, developed, and fully characterized. The 3D‐printing of nanomaterials on skin‐like flexible substrates is innovatively applied to enable multimaterial and multilayer printing of the sensors, reusable electronic/communication circuity, and antennas in a tailorable, low‐cost, and time‐efficient manner. The battery‐free and flexible readout system is designed to enable wireless and on‐demand energy and data transmission for continuous and real‐time pH monitoring. This sensor system exhibits high sensitivity (≈|51.76| mV pH⁻¹), specificity, repeatability, reproducibility toward various pH ranges (3.0–10.0), excellent mechanical flexibility, and outstanding biocompatibility (cell viability > = 90%). It successfully demonstrates the pH change monitoring in an ex situ hydrogel‐based wound model. The WB²F3D sensor system is envisioned to provide an integrated platform for accurate, on‐demand, battery‐free, wireless, and real‐time human health monitoring, and another step toward personalized medicine.