A needle-free bubble injector enabling depth-controlled isotropic and anisotropic perforation using electrically induced bubbles and heat generated by electric discharge.

Transdermal drug delivery is advantageous in administering therapeutic agents, such as many vaccines and macromolecular drugs that do not remain in the body after oral ingestion. Needle-free injectors have been developed as an alternative to the existing syringes for drug delivery; however, because of the difficulties in controlling the jet flow during perforation, their practical use remains a challenge. Herein, we propose a novel needle-free injector. By controlling the distance between the target and the device, the injector performs (i) isotropic perforation using electrically induced bubbles or (ii) anisotropic perforation using localized heating generated by electric discharge at the device tip. Furthermore, by controlling the applied voltage, the size of the electrically induced bubble and the speed of the microjet generated by bubble collapse can be regulated. As a result, the perforation depth was controlled in the range of 0.7-1.1 mm, which is difficult to achieve using conventional needle-free injectors. These results indicate the potential of the proposed method for precise and minimally invasive transdermal drug delivery.