Volume 122, Issue 4, October 2007
Index of content:
- TRANSDUCTION 
122(2007); http://dx.doi.org/10.1121/1.2769980View Description Hide Description
Circular cymbalultrasound arrays have been shown to be effective in deliveringtherapeutic levels of insulin in rats, rabbits, and pigs. To improve delivery efficiency, a rectangular cymbal design was desired in order to achieve a broader spatial intensity field without increasing the size of the device or the spatial-peak temporal-peak intensity . With a similar intensity , the goal was to determine if the rectangular cymbal array could perform significantly better than the circular array for glucose reduction in hyperglycemic rabbits. Rabbit experiments were performed using three groups: nonsonicated control , ultrasound exposure using a circular cymbal array , and ultrasound exposure using a rectangular cymbal array . Rabbits were anesthetized and a water tight reservoir that held the insulin was fastened on the rabbit’s thigh. At the beginning of the experiment and every for , the blood glucose level was determined. For comparison between individual rabbits, the absolute level is normalized by subtracting out the baseline in order to arrive at the change in glucose level. For the control group, the normalized glucose level increased (more hyperglycemic) to . Using the circular array, the glucose level decreased to at . However, using the rectangular cymbal array, the glucose decreased faster and to a level of after . These results indicated the feasibility of the rectangular cymbal array as an improved device for drug delivery.
122(2007); http://dx.doi.org/10.1121/1.2769615View Description Hide Description
Micromachined microphones with diffraction-based optical displacement detection have been introduced previously [Hall et al., J. Acoust. Soc. Am.118, 3000–3009 (2005)]. The approach has the advantage of providing high displacement detection resolution of the microphone diaphragm independent of device size and capacitance—creating an unconstrained design space for the mechanical structure itself. Micromachined microphone structures with polysilicon diaphragms and monolithically integrated diffraction gratingelectrodes are presented in this work with backplate architectures that deviate substantially from traditional perforated plate designs. These structures have been designed for broadband frequency response and low thermal mechanical noise levels. Rigorous experimental characterization indicates a diaphragm displacement detection resolution of and a thermal mechanical induced diaphragm displacement noise density of , corresponding to an A-weighted sound pressure level detection limit of for these structures. Measured thermal mechanical displacement noise spectra are in excellent agreement with simulations based on system parameters derived from dynamic frequency response characterization measurements, which show a diaphragm resonance limited bandwidth of approximately . These designs are substantial improvements over initial prototypes presented previously. The high performance-to-size ratio achievable with this technology is expected to have an impact on a variety of instrumentation and hearing applications.