Large-scale fully printed “Lego Bricks” type wearable sweat sensor for physical activity monitoring

Wearable sweat sensors are becoming increasingly popular for their biorecognition capabilities in non-invasive, dynamic, and continuous real-time monitoring of biological information. Real-time monitoring of large-scale samples is crucial for realizing intelligent health. A major bottleneck for enabling large-scale sweat eluidication is the fabrication of wearable sensors equipped with microfluidic devices and flexible electronics in a cost-effective, homogeneous performance and rapid large-scale way. Herein, a “Screen+Wax” printing technique was introduced to prepare these components and construct “Lego Bricks” type wearable sweat sensor to monitor sweat Na⁺ and K⁺. Flexible electrode arrays and paper-based microfluidic layers (they act as building blocks) were fabricated on polyethylene terephthalate and paper surfaces, respectively, using screen printing and wax printing. Gold nanoparticles and Na⁺/K⁺ ion-selective membranes were modified on the electrode surfaces by electrodeposition and drop coating, respectively. In this work, we highlight the excellent performance of the “Lego Bricks” type wearable sweat sensor in testing the Na⁺ and K⁺ imbalance of sweat from different body regions during exercise and, more significantly, to track the physical activity during prolonged exercise under different interventions. Furthermore, the prepared “Lego Bricks” wearable sweat ion electrochemical sensor is demonstrated to be capable of large-scale samples elucidation with outstanding performance and cost-effectiveness, which is expected to deeply integrate sweat monitoring into physical activity, providing an important tool for intelligent health.