Figure 18.

The cymbal transducer made of piezoelectric material lead zirconate-titanate (PZT)-4 operated at a frequency of 20 kHz. The cymbal disk was placed between two titanium caps with air cavities beneath the caps, which convert the radial oscillations of the disk into flexure motions of the caps. Graph of the change in blood glucose over the 90-min transdermal insulin delivery experiment duration, comparing both controls (insulin only and ultrasound only) to the insulin and ultrasound results generated by the 2 × 2 array (insulin and ultrasound 2 × 2) and 3 × 3 array (insulin and ultrasound 3 × 3) [51].