An example device includes a microfluidic channel and a movable element retained in the microfluidic channel to move from a first position to a second position by fluid flow through the microfluidic channel. The device includes a sensor to take a sensor reading to determine fluid flow through the microfluidic channel. The device includes a microfluidic pump to return the movable element from the second position to the first position. The device includes a controller to actuate the microfluidic pump and to determine a flow rate of the fluid flow through the microfluidic channel based on the sensor reading.