Development and application of p-NIPAM Barriers and Repositories for Microfluidic Flow Control. A Proof of Concept

Abstract

Passive fluid flow is not sufficient to meet new analytical requirements, therefore further research is needed in the field of flow control in order to improve the application of microfluidic systems. In this work, stimuli-sensitive materials have been studied to act as barriers and repositories to be integrated in µPADs. Poly(N-isopropylacrylamide) (p-NIPAM) has been studied to act as a reservoir and flow retardant. As a reservoir, the swelling/de-swelling behaviour has been characterised as a function of temperature, kinetics, reservoir size and the influence of pH. As a flow retardant, a p-NIPAM ionogel was used to significantly slow down the flow and even stop it. This is very useful for preventing the mixing of reagents until a certain point in time or for controlling where the mixing occurs. The ionogel volume and the delay time were optimised. As proof of concept, they were used in a colorimetric µPAD for nitrite determination based on the Griess chemistry. The results demonstrate the feasibility of integrating the developed stimulus-sensitive materials in µPADs, enabling new applications where these tools are required.