A Miniature 16-element Endoscopic Histotripsy Transducer with Electronically Steerable Focus

A 5 mm by 5 mm 16-element histotripsy transducer was built and tested using a lens bonded to an air-backed 1-3 piezoelectric composite. The transducer was driven by a custom designed 16 channel pulse generator. Both aluminum and methacrylate photopolymer (resin) lens designs were modelled using a COMSOL FEM model. A resin lens was 3D printed and used to fabricate a transducer array with a focus that could be steered over a greater area than the aluminum lens design. The resin lens transducer had a peak negative pressure trend of 5.7 MPa/100 V. The -3 dB focal length and width were 1.94 mm and 0.30 mm. A pulse sequence cycling through 5 foci spaced within a 1.5 mm square was used to ablate ex vivo rat brain tissue through shock scattering cavitation near the surface.