Sample preconcentration from dilute solutions on micro/nanofluidic platforms: A review

Biochemical detection plays a critical role in many analytical fields. For example, blood samples include many proteins with relevance to disease diagnosis and therapeutic monitoring. Foods and beverages contain a large number of chemicals and compounds which must be quantified and characterized to ensure their compliance with safety standards. Detecting trace amounts of contaminants in ambient air or water samples is essential in monitoring the environment and protecting human health. Therefore, effective techniques for performing the rapid and reliable detection of targeted analytes are required. Compared to conventional macroscale devices, microfluidic systems have many advantages, including a greater sensitivity, a faster response time, a reduced sample and reagent consumption, and a greater portability. Accordingly, many microfluidic systems for sample detection have been proposed in recent years. The performance of such devices relies on the target analyte being present in a sufficient concentration to enable its detection. In many biomedical, food testing and environmental applications, the detection limit was restricted. Thus, the sample must first be concentrated before the detection process is carried out. Accordingly, this review provides a comprehensive review of recent advances for sample preconcentration with emphasis on utilizing ion concentration polarization (ICP) effects in micro/nanofluidics platforms. We start with a brief introduction regarding the importance of preconcentration using micro/nanofluidics platforms, followed by in-depth discussions of the ICP effects for the preconcentration and applications to biomedical analysis, food testing and environmental monitoring. Finally, the article concludes with a brief perspective on the future development of the field.