High aspect ratio integrated force arrays

The Integrated Force Array (IFA) is a metallized polyimide actuator made up of a large array of capacitive cells that deform when voltage is applied. The deformations of the individual cells add to produce an overall muscle-like compression of the array. In previously reported work deformations of up to 30% have been realized and the IFAs have been used as mechanical scanners in ultrasound imaging systems. The gaps of the capacitive cells are etched directly into the polyimide and oriented perpendicular to the plane of the array. Metal is deposited on the sidewalls of the etched features in order to form the plates of each capacitor. The force associated with the IFA motion is directly proportional to the height of the sidewall metal and thus to the thickness of the membrane. Until now, the thickness has been 2μm with gap widths of 1μm. In recent work, much higher aspect ratio IFAs (thicker but with the same gap width) have been fabricated in order to produce devices that operate with greater force and are much more robust devices.