Evaluation of heavy metal contamination: an analogy between conventional techniques and paper microfluidics as the futuristic probe for diverse environmental matrices

In recent decades, massive exudation of heavy metals into natural water bodies has become prevalent world wide, posing threat to the environment, individuals and their well-being. Owing to its prolonged half-life and non-biodegradability, potential accumulation of heavy metals can cause serious health problems. Several cutting-edge diagnostic methods are being utilized for the assay of heavy/toxic metals. Certainly, these methods hold some limitations, such as requirement for extortionate devices and strenuous operations that can only be carried out in laboratories. This led to the emergence of detection methods based on sensors. Among various breakthroughs, paper-based analytical devices as well as paper-based microfluidic devices have turned up as one of the economical, convenient, easily disposable and portable substitutes for on-site detection. This study discusses the current analytical methods and paper-based devices used for heavy metal detection in the first phase followed by the discussion on comparative analysis of various analytical methods. In addition, there are techniques for heavy metal detection, which use substrates like paper, polydimethylsiloxane, etc. using colorimetric, fluorescence or electrochemical sensing, have also been discussed. The development of programmable paper-based microfluidic devices has been emphasized in the second phase of the discussion. Finally, the future progressions and developments in this field have also been proposed.