Many applications in microelectromechanical systems require physical actuation for implementation or operation. On-chip sensors would allow control of these actuators. This paper presents experimental evidence showing that a certain class of thermal actuators can be used simultaneously as an actuator and a sensor to control the actuator's force or displacement output. By measuring the current and voltage supplied to the actuator, a one-to-one correspondence is found between a given voltage and current and a measured displacement or force. This integrated sensor/actuator combination will lead to efficient on-chip control of motion for applications including microsurgery, biological cell handling, and optic positioning.