Proof of Concept (IMAGE) University of Sussex Caption The device uses 'time-reversal' processing to send ultrasound waves through the hand. This technique is effectively like ripples in water but in reverse -- the waves become more targeted as they travel through the hand, ending at a precise point on the palm. Credit Sri Subramanian / University of Sussex Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.