A carrier device and methods of use, for implanting in biological tissue andreleasing a medical payload in the biologicaltissue according to remote ultrasound trigger pulses. The carrier deviceincludes at least one internal resonant element with a resonancefrequency in the ultrasound range. When an ultrasound pulse at the resonancefrequency is sent through the tissue, the resonant elementvibrates at high amplitude and raises the internal pressure of the carrier andreleases the payload. In some embodiments, payload releasecan be started, stopped, and restarted at a later time or place. Individualcarrier devices can be selectively triggered by providing differentresonance frequencies, and external resonant elements can provide propulsionand navigation capabilities.
