Electrical contactless microfluidic flow quantification

Precise sensing of microfluidic flow is essential to advancing lab-on-a-chip development and the downstream medical applications. Contactless microfluidic flow interrogation is noninvasive, nonperturbative, and fouling-free. However, known real non-contact flow sensing technologies are limited to quantifying bulk fluids. Here, we develop an electrical approach to contactless quantification of aqueous microfluidic flow. We found that the electric potential generated by the ubiquitous contact electrification of a microfluidic flow with fluidic channel walls is interrogatable by using a probe electrode at a distance over centimeters from the microfluidic flow, and the measured voltage response demonstrates linear relationship to the microfluidic flow rate with a resolution of sub-microliter per minute (in a 1-Hz bandwidth), providing an ideal, high-precision contactless flow transduction pathway. In addition to this primary finding, by using a monolayer-graphene coated probe electrode, in comparison with a typical bare probe electrode, an overall enhancement in flow-sensory resolution of 36.4% is attained.