Microfluidic switching devices showing controllable hysteresis

We present a microfluidic MEMS device that is capable of switching among different states, thus behaving as an effective flip-flop. The devices consist of linear microfabricated deLaval nozzles with three exit channels, and we analyze the response as a function of input and output pressures, feed gas, and dimensions. In all cases, we have seen the appearance of a vortex, whose direction of swirl changes sign according the input pressure, and showing hysteresis. This type of response can be used to realize history-aware fluidic devices.