Energy-Efficient Micromixing in Paper Based Devices Mediated by the Interplay of Electrical and Thermal Fields

Biomedical and biochemical processes in paper-based microfluidic devices often deal with mixing of two analytes to perform important functions. Uniform mixing of analytes in paper matrix is a challenging proposition, often necessitating complicated channel design or high energy external fields for realizing the desired functionality. In sharp contrast, here we demonstrate an energy-efficient technique compatible with handing biofluids, to achieve a high level of mixing of two fluids in paper-based microfluidic devices without deploying complex channel shapes. Our method employs a simple, cost-effective printing-based method to fabricate paper channel with interdigitated electrodes laid out using pencil sketch. An alternating current electric field of sufficiently low voltage is used to generate perturbations on the interface of the two fluids streams undertaking spontaneous capillary imbibition. The consequent variations in electric field generate local thermal gradients, leading to localized volumetric forces triggering efficient fluid mixing. Our results find a wide variety of applications ranging from biochemical analysis to medical diagnostics.