Advances in the noninvasive and minimally invasive sample collection for wearable electrochemical sensors

Wearable electrochemical sensors, which can track various biomarkers in real-time, is one of the most promising bioanalytical devices in the point of care testing and health management. Sample collection modules, as the important front-end of the sensors, capture and transfer enough sample so as to achieve real-time, precise and accurate detection. Noninvasive and minimally invasive techniques for sample collection are highly desired. However, it is still a key challenge to realize a reliable sample acquisition. Herein, we provide an overview on the progress in the sample collection methods for wearable electrochemical sensors. It covers the conventional and emerging methods/structures including reverse iontophoresis, microneedles, as well as microfluidic chips. The working principle, fabrication materials and manufacturing technologies will be introduced in detail. Finally, the present challenges and the development trend in the future of these approaches are also put forward.