Synthetic muscle actuators: Applications in ultrasonic imaging and optical beam steering

There is much interest in the biomedical community in mechanically steering both high frequency ultrasound transducers and various optical beams. We are currently investigating the use of two different types of MEMS actuators, integrated force arrays (IFAs) and spiral wound transducers (SWTs). The IFA is a linear actuator that is a parallel network of hundreds of thousands of flexible capacitors that electrostatically contract, and the SWT is a patterned tape that is wound to form a circular network of flexible capacitors that can be electrostatically compressed to tilt desired structures. Using ANSYS finite element analysis, we have developed tilting polyimide support structures, which are fabricated on silicon wafers. High frequency ultrasound transducers (20-30 MHz) have been built on these structures and IFAs used to tilt them to steer the ultrasound beam in fluids. Prototype structures have produced 20 degree sector scans scanning at frequencies up to 30 Hz. IFAs have also been used along with similar support structures to steer optical laser beams up to 45 degrees at frequencies up to 60 Hz. The SWT is a more recent development that operates with much greater force than the IFA that could steer ultrasound and optical beams for similar applications.