Systems and methods for the construction of electric motors, where expandable material is inserted into the slots in which magnet wires are positioned and expanded in the slots to mechanically restrain the wires. One embodiment comprises a downhole electric motor such as might be used in an electric submersible pump (ESP) system. The motor has a stator with multiple slots in which magnet wires are positioned. A slot liner is positioned in each slot and an expansion pad is positioned in each slot between the slot liner and the slot wall nearest the bore of the stator. The wires are positioned inside the slot liner. When the motor is almost completely assembled, it is filled with oil. Some of the oil is absorbed by the expansion pads, which then expand to fill the unoccupied volume in the slots, thereby restraining the movement of the wires within the slots.