The present disclosure is drawn to microfluidic devices. In one example, a microfluidic device can include a driver chip and a fluid chamber located over the driver chip. First and second microfluidic loops can have fluid driving ends and fluid outlet ends connected to the fluid chamber. The first and second microfluidic loops can include a portion thereof located outside a boundary of the driver chip. A first fluid actuator can be on the driver chip associated with the fluid driving end of the first microfluidic loop to circulate fluid through the first microfluidic loop. A second fluid actuator can be on the driver chip associated with the fluid driving end of the second microfluidic loop to circulate fluid through the second microfluidic loop.