The scope of this work has been the design of a mechanical actuator in polydimethylsiloxane (PDMS) / glass for precise liquid sampling, based on the electrochemical generation of O2. The device is composed of two chambers separated by a PDMS membrane. In the first chamber, the generated gas bends the membrane, actuating a precise volume of a liquid sample in the second chamber. The linear relationship between the number of transferred charges and the number of gaseous O2 molecules allows a very accurate control of the dispensed volume.