A Large-Stroke MEMS Deformable Mirror Fabricated by Low-Stress Fluoropolymer Membrane

This letter presents a deformable mirror (DM) which consists of a 25-mm square flexible membrane and an array of 67 hexagonal electrodes that can pull down a membrane by electrostatic force. The membrane is a 2.15-mum-thick fluoropolymer film and is bonded to an electrode substrate with an 80-mum-thick adhesive acrylic spacer. The fabrication process is completed by a microelectromechanical systems batch process. The surface roughness of polymer membrane is approximately 41 nm. The device demonstrated maximum 38-mum center deflection by applying 250 V because of small residual stress (2.2 MPa) and low Young's modulus (15 GPa) of fluoropolymer film. The response time of the DM is experimentally demonstrated around 10 ms in atmosphere. The proposed device is suitable for large stroke and low sampling rate applications.