Disclosed herein are microfluidic actuators for selecting objects in a fluid stream comprising a plurality of objects. In some embodiments, the actuator comprises an object detection means adapted for, upon arrival of an object, identifying whether an object is an object of interest. It further comprises a heater adapted for generating a jet flow for deflecting an object of interest from the fluid stream and a controller for activating the heater as function of the detection of an object of interest using a nucleation signal. The controller is adapted for obtaining temperature information of the heater and for adjusting a nucleation signal for the heater taking into account the obtained temperature information. Also disclosed are microfluidic systems and diagnostic devices comprising the microfluidic actuators of the disclosure, as well as methods of use thereof.