Using two separate beams of inaudible sound waves (one at low-frequency, the other high) the team were able to increase the permeability of skin, in a bid to improve the efficiency of transdermal drug delivery.
The technique works thanks to the waves exciting bubbles in a fluid (such as water), forcing them to swell and move chaotically. Once the bubbles reach a certain size they implode, sucking the surrounding fluid into the void. This process creates micro-jets of liquid, which cause miniscule tears in the skin, allowing it to (painlessly) absorb chemicals more effectively.
…Up until now, research into ultrasonic administration of drugs has concentrated on low-frequency waves, because the higher end of the spectrum doesn’t have enough energy to pop the bubbles. Higher frequencies do, however, help create more of them and also limits their lateral movement.
[U]sing both high- and low-frequencies.. produced better overall results, by not only increasing the skin’s uptake of the medicine, but also increasing the number of drugs that can be delivered this way.