  In this work we show that in a microfluidic network and in low Reynolds
numbers a system can be irreversible because of hysteresis effects.The network,
which is employed in our simulations, is taken from recent experiments. The
network consists of one loop connected to input and output pipes. A train of
droplets enter the system at a uniform rate, but they may leave it in different
patterns, e.g. periodic or even chaotic. The out put pattern depends on the
time interval among the incoming droplets as well as the network geometry and
for some parameters the system is not reversible.
