See magnetostriction. Magnetostriction is employed in some anti-theft and RFID tags and now it is being considered for energy harvesting. So far, there is no way of printing magnetostrictive materials to save cost, because they physically move in use. To use other words, magnetostriction is the movement of certain magnetically responsive materials under an electric field. The hum of a transformer is one example of a magnetostrictive effect. It may be an alternative to piezoelectrics in some vibration harvesting applications but it is experimental as yet. North Carolina State University believes that its magnetostrictive materials can beat piezoelectrics in some applications because they advantages including ultra-high energy conversion efficiency, high power density, longer life cycles without the depolarization issue, and flexibility to operate in strong ambient vibrations.