It’s difficult with helium because the atom is so small that it can effectively penetrate the gaps in the atomic structure of almost any solid material given time. Even solid iridium can have small amounts of helium leach through.
Re ultrasonics - for some MEMS devices yes this can absolutely break things, but because the devices are so small, the resonant frequencies can often be in the hundreds of KHz or even MHz and most ultrasound transducers only produce sub 100khz frequencies
Re ultrasonics - for some MEMS devices yes this can absolutely break things, but because the devices are so small, the resonant frequencies can often be in the hundreds of KHz or even MHz and most ultrasound transducers only produce sub 100khz frequencies