Ultrasonic wedges for elastic wave bending and splitting without requiring a full band gap

We present a novel twinned-square periodic structure for ultrasonic wave bending and splitting that does not require the existence of a complete band gap and plays the role of an ultrasonic wedge. The device allows 45 degrees bending of waves and by adequately switching the twinned structure to an ultrasonic crystal 90 degrees bending is achieved. An extreme refraction law at the grain boundaries is experimentally observed.