Crawling waves from radiation force excitation.

Crawling waves are generated by an interference of two oscillating waves traveling in opposite directions, with a progressive movement resulting from a frequency difference or a phase difference between the sources. While the idea has been applied to numerous applications, all the previous reports used mechanical sources to vibrate the medium. It is shown, through experiments and simulation, that crawling waves can be generated from focused beams that produce radiation force excitation within the tissue. Some examples are also shown.