" An essential part of evaluating the success of global health is the access to appropriate diagnostic tools.1 A commendable diagnostic tool should be able to rapidly identify disease occurring in individuals. Especially for infectious diseases, the turnaround time strongly affects their level of transmission to the community. In vitro diagnostic (IVD) tools aim to offer a comfortable experience for patients, by taking only a small specimen from the human body, e.g. blood, urine, sputum, and tissue. Consequently, technologies enabling effective in vitro diagnosis have become highly attractive in both developed and developing countries.2 Tremendous efforts have been geared towards clinical-level IVD tools. Despite achieving high accuracy, the result turnaround time can be too long for contagious diseases like Ebola and SARS, and the need for skillful operators to perform the assays can dramatically raise the cost.
Recently, decentralized diagnostic solutions, namely point-of-care (PoC) devices, have gained notable interest, which is attributed to their rapidity, small footprint and tiny sample usage. A wide variety of diagnostic platforms have been invented, such as lateral flow assays3–6 and the path-breaking lab-on-a-disc7–10 for PoC applications. Beyond these, PoC devices on Complementary metal oxide semiconductor (CMOS) chips are particularly promising, as they can enjoy the maturity of microelectronics in manufacturing, and its outstanding performances in both physical sensing and signal processing. While the mainstream lateral flow assay is limited to providing merely qualitative or semi-quantitative results,11 CMOS biosensors can attain quantitative results and are beneficial to rapid and low-cost assays. Especially for low-cost IVD applications, CMOS chips on a centimeter scale can significantly miniaturize diagnostic tools."
