Comparison of Fresnel lens-based focused vortex transducer and focused transducer for neurostimulation

The most common neurostimulation method is the stimulation of the focal point by using a focused ultrasound transducer. In the field of particle manipulation using ultrasound, research using acoustic vortices is ongoing and presents promising characteristics. In neurostimulation using ultrasound, the acoustic radiation force is a leading candidate for a physical mechanism. In this study, the acoustic radiation forces generated by a general-focused transducer and a vortex transducer were compared. For the experiment, a 70 mm diameter transducer with a center frequency of 1 MHz was fabricated using a piezoceramic plate. The ultrasound transducer frame was made of aluminum, and air backing was used to maximize the output pressure. A large-scale Fresnel focused lens and focused vortex lens were fabricated using polydimethylsiloxane (PDMS). A mold of an 8-step Fresnel lens with a diameter of 70 mm was developed using 3-D printing. We compared the pressure field and radiation force according to the two manufactured lenses to determine whether there was any difference in neurostimulation.