A method and system of controlling the temperature of a refrigeration system. In an embodiment, an expansion valve for a refrigeration system comprises an entry portion, an exit portion, and a flow control portion including a piezo material. The entry portion is configured to allow refrigerant to flow into the expansion valve. The exit portion is configured to allow refrigerant to flow from the expansion valve. The flow control portion is disposed between the entry portion and the exit portion, and is configured to control a volume of refrigerant that passes through the expansion valve.