Hybrid MEMS-SMA structure for intraocular lenses

This paper presents the design, fabrication and evaluation of a novel ring-shape MEMS micro actuator for a latching mechanism for low power consumption and large displacement linear actuation, which can be applicable for a variable-focus lens system such as an accommodative intraocular lens (AIOL). The proposed actuator consists of a shape-memory-alloy (SMA) ring, parylene spring and shoes. The parylene spring was carefully designed for independent control of radial and axial stiffness, which can be realized by a high aspect ratio cross section and a meander structure. The maximum force generated by the parylene spring was about 50 mN. Two types of SMA actuator have been examined for the actuation: simple wire and micro spring types. The SMA in wire shape was evaluated in two configurations. Maximum displacement as high as 300 μm was obtained by using the SMA micro spring.