Heavy metal ion detection and extraction using paper-based atom stamp printed devices

Microfluidic paper-based analytical devices (µPADs) are a promising concept with rapid development in recent years. In a new study published on Nature: Microsystems & Nanoengineering, a team led by Yanfang Guan and Baichuan Sun in electromechanical engineering in China, developed a new technique to engineer µPADs known as atom stamp printing (ASP). The method was cost-effective, easy to operate and allowed high production efficiency with high resolution. As a proof of concept, they used µPADs engineered via the ASP method to detect varied concentrations of copper (Cu2+) via a colorimetric method. The devices achieved a Cu2+ detection limit of 1 mg/L. Guan et al. also created a new paper-based solid-liquid extraction device (PSED) using a three-dimensional (3-D) µPAD with a "3+2" structure and recyclable extraction mode. Due to the characteristics of paper filtration and capillary force, the device could efficiently complete multiple extraction and filtration steps from solid-liquid extraction processes. The PSED platform allowed simple, cost-effective and fast heavy metal ion detection at point-of-care. The work has great promise for applications in food safety and environmental pollution in resource-limited areas.