This invention discloses an apparatus and method for producing microcavitational activity in aqueous fluids for non-invasive 
macromolecule delivery into living cells. A standard electrohydraulic 
shock wave lithotripter is fitted with an adjustable ring reflector that shares the same foci as the standard lithotripter hemi-ellipsoidal reflector. A small portion of the spherical 
shock wave, generated by the 
spark discharge at the first focus (F1), is reflected and diffracted by the ring reflector, resulting in a weak preceding 
shock wave approximately 8.5 mus in front of the lithotripter shock wave reflected and diffracted by the hemi-ellipsoidal reflector. The peak negative pressure of the preceding weak shock wave or pulse at F2 can be adjusted from -0.96 to -1.91 MPa, using an output 
voltage of 25 kV. Living cells are exposed to the preceding shock wave and the lithotripter shock wave. With optimal pulse combination, the 
maximum efficiency of shock wave-induced 
cell membrane permeabilization can be enhanced substantially (up to 91%), by applying to the living cells a low dosage of, for example, 50 shocks. In addition, injury to mouse lymphoid cells is significantly increased at 
high dosage (up to 50% with shock number >100). The invention thus enables shock wave-inertial microbubble interaction to be used selectively to either enhance the efficiency of shock wave-mediated 
macromolecule delivery at low dosage or tissue destruction at 
high dosage.