A carrier device and methods of use, for implanting in biological tissue and releasing a medical payload in the biological tissue according to remote ultrasound trigger pulses. The carrier device includes at least one internal resonant element with a resonance frequency in the ultrasound range. When an ultrasound pulse at the resonance frequency is sent through the tissue, the resonant element vibrates at high amplitude and raises the internal pressure of the carrier and releases the payload. In some embodiments, payload release can be started, stopped, and restarted at a later time or place. Individual carrier devices can be selectively triggered by providing different resonance frequencies, and external resonant elements can provide propulsion and navigation capabilities.
