Terahertz imaging technique for monitoring the flow of buffer solutions at different pH values through a microfluidic chip

Polydimethylsiloxane (PDMS)-based mold prepared using a 3D-printed structure is a cost-effective material and tool to fabricate robust microfluidic chips (MCs) without requiring expensive clean room facilities. A capillary-based MC made of PDMS can be attached onto a glass substrate to visualize the chemical reactions in different types of pH buffer solutions (BSs) flowing through microflow channels (MFCs) using terahertz (THz) image sensing technology. In this study, we designed a microfluidic structure with two inlet wells and an outlet well, equipped with a Si:sapphire substrate to visualize the chemical interaction between BSs injected at different pH values (4 and 10) through an MFC. THz imaging maps were captured during the flow of the BSs using a THz chemical microscope, and the fluid dynamics was studied. We determined and plotted the variation in the THz amplitude data with respect to the BS concentration and analyzed the characteristics of the data.