Thermal vertical bimorph actuators consist of silicon beams side-coated with aluminium. Upon heating they bend like a bimetal and produce movement in the wafer plane. We have measured the time constant describing the deflection response of the actuator to input pulses. Depending on the dimensions of the actuator, the time constant ranges from 0.5 ms to 3.8 ms. Lateral resonances of the first mode have been measured using thermal excitation and are found to be between 20 and 85 kHz.