Distance versus Capillary Flow Dynamics‐Based Detection Methods on a Microfluidic Paper‐Based Analytical Device (μPAD)

Abstract

In recent years, there has been high interest in paper‐based microfluidic sensors or microfluidic paper‐based analytical devices (μPADs) towards low‐cost, portable, and easy‐to‐use sensing for chemical and biological targets. μPAD allows spontaneous liquid flow without any external or internal pumping, as well as an innate filtration capability. Although both optical (colorimetric and fluorescent) and electrochemical detection have been demonstrated on μPADs, several limitations still remain, such as the need for additional equipment, vulnerability to ambient lighting perturbation, and inferior sensitivity. Herein, alternative detection methods on μPADs are reviewed to resolve these issues, including relatively well studied distance‐based measurements and the newer capillary flow dynamics‐based method. Detection principles, assay performance, strengths, and weaknesses are explained for these methods, along with their potential future applications towards point‐of‐care medical diagnostics and other field‐based applications.

Recent advances in paper‐based preconcentrators by utilizing ion concentration polarization

“…Paper is cheap, multi-functional, and scalable when used for diagnosis [64]. These characteristics are important requirements for real-time diagnosis, particularly in areas of the world with limited resources; therefore, μPADs [65] have received significant attention [66][67][68][69]. The earliest paper-based materials are mainly composed of cellulose.…”

Clarity improvement of the discoloration boundary and detection of Hg2+ ions by using a polystyrene nanoparticle-modified paper-based microdevice

“…However, they still require other instruments and equipment to convert the detection results into readable data. [1][2][3][4][5] Such equipment is usually expensive and complicated to operate, usually requiring trained professionals. Distance-based mPADs have wide application prospects in less developed countries given their easy operation and naked-eye detection.…”

Enhanced functional DNA biosensor for distance-based read-by-eye quantification of various analytes based on starch-hydrolysis-adjusted wettability change in paper devices

“…In particular, the distance-based detection strategies with the ruler have been well-recognized to be capable of achieving the ultimate economic goal of quantifying targets without the use of any electronic readers for applications especially in resource-poor settings in either the developing world or developed countries. [45][46][47][48][49] Herein, we respond to this challenge by initially describing the proof-of-concept of a new functional DNA biosensor for equipment-free, read-by-eye quantication of adenosine, interferon-g and Pb 2+ ion as three types of model analytical targets. This sensor integrates enzyme-coated microbeads for efficient signal amplication with distance measurement on mPADs based on starch-hydrolysis-adjusted wettability change of paper body for portable quantitative readout.…”