Field Effect Transistor-Like Control of Capillaric Flow Using Off-Valves

An important application area of microfluidics is point-of-care devices. Capillaric circuits are a promising technology to realize such devices. Recently, we introduced a capillary action off-valve which adds pre-programmed autonomous “off’-type valving as a unit operation to capillaric circuits. To date, these devices have only been shown to operate in binary mode. However, due to its conceptual symmetry with electronic junction field effect transistors, it was hypothesized that the off-valve was capable of providing analog resistance control. Using an experimental approach, this work demonstrates for the first time that capillary off-valves can operate in analog resistance mode and that flow control results can be fitted using a modified model of the Shockley transistor equation.