Method to prevent backflow in a capillarity network for bioassays: Exploiting time constant ratios

Abstract

Abstract In order to achieve highly sensitive, multiplexed bioassays, the number of channels and input solutions in a capillarity-driven device must be increased, which thereby also increases the risk of occurrence of malfunctions. Here, we present a method to prevent unwanted backflow, which is a critical problem that prevents the successful detection of target analytes in a capillarity network. Through the use of a linearized model of the network’s inlet pressures, we show that backflow originates from the difference in time constant ratios of the network’s inlet-channel elements. More importantly, we demonstrate that backflow can be prevented by sequentially increasing the time constants of the network elements where solution is injected. Also, we show that the initial inlet pressures do not influence the generation of backflow and only affect its magnitude. Similarly, by considering the fluidic conductances and time constants to be independent and setting the inlet radii as dependent parameters, we show that the fluidic conductance of each channel also contributes to the magnitude of the backflow without influencing its generation. We believe that the material presented here will be crucial for the control of capillarity in complex fluidic networks and in more sophisticated capillarity-driven bioassays.