Abstract by Lucas Barnes
Physics and Astronomy
Knocking over LEGO minifigures as a demonstration of focusing vibrations using time reversal
Time reversal (TR) is a method of focusing wave energy at a single point in space. This project optimizes a TR demonstration designed to knock over one selected LEGO minifigure among other minifigures by focusing vibrations at the target minifigure. By comparing the motion of the minifigure and the plate directly beneath its feet, it was determined that a major factor inhibiting the repeatability of the demo was that smaller vibrations before the focal event were causing the minifigure to lose contact with the plate and bounce repeatedly, often missing the main focal event. The use of more vibration sources, limited amplitudes, and a specific range of frequencies greatly improves the repeatability of the demonstration. This demonstration illustrates the power of TR focusing and the principles learned by optimizing this demonstration can be applied to other real-world applications. Applications include finding defects in structures, lithotripsy of kidney stones, and secure SONAR communication.