Magnetically Assisted Additive Manufacturing for Freeform Optics

Primary author: Mojtaba Falahati
Faculty sponsor: Dr. Roland Chen

Primary college/unit: Voiland College of Engineering and Architecture
Campus: Pullman

Abstract:

In modern optical systems, freeform optical components are used to modify the focal length or to correct the wavefront. For instance, wavefront control and correction has been always a critical issue in adaptive astronomical telescopes. Freeform lenses are optical correctors which are widely used to improve the optical performance through the aberration correction. Traditional optical manufacturing techniques such as machining, molding and casting processes demand sophisticated and expensive equipment. Here we introduced magnetism and interfacial force into Additive Manufacturing to develop tunable magnetic liquid molds for rapid, low-cost and straightforward fabrication of freeform lenses. Using customized extrusion-based 3D printers, a magnetic ink was printed either within an immiscible optical elastomeric environment such as polydimethylsiloxane (PDMS) or on a cured elastomeric substrate. The profile shapes at the liquid-fluid interface were regulated using an external adjustable magnetic field. Depending on the field configuration, various freeform optical surfaces can be generated during printing process that served as tunable liquid molds to shape the surrounding optical elastomer into a concave aspherical lens after curing. An apparatus was assembled to provide different magnetic force and to control the gradient of applied magnetic field on the droplets. A home-built Shack-Hartmann sensor was employed to measure the focal length of the formed lenses and the lens profiles were extracted using an axisymmetric drop shape analysis (ADSA). The effects of magnetic field intensity, gradient of magnetic field, and magnetic susceptibility were investigated. This technique can be used for forming lenses with different sizes, shapes and magnifications.