New Lens Fabrication Technique Uses Magnetic Liquid Molds

Researchers from Washington State University and Ohio State University have developed an inexpensive way to make custom lenses. They developed soft, deformable molds from droplets that can be manipulated with magnets to create lenses in a variety of shapes and sizes.

The researchers first tried to make their own lenses using 3D printing but found it difficult to control the lens shape. They then discovered a way to use magnets and the surface tension of liquids to create free-flowing molds.

Lei Li (l), assistant professor, and graduate student Mojtaba Falahati developed a low-cost, straightforward method to make custom lenses. Courtesy of WSU.

The team placed tiny, magnetic iron particles into liquid droplets and built a device to control the amplitude and gradient of the magnetic field. The magnetic drop, when placed within a polymeric resin, formed a conical shape due to the equilibrium of magnetostatic force and surface tension, which resulted in a plano-concave lens after curing. The researchers used a sensor to measure the focal length of the formed lenses. The effects of magnetic field intensity, the gradient of the magnetic field, and the magnetic susceptibility were investigated.

Graduate student Mojtaba Falahati holds a homemade lens made using a magnetic liquid mold. Courtesy of WSU.

According to the team, the handmade lens was found to have the same optical properties and imaging quality as a commercially purchased lens. The liquid droplets remained separate from the formed lens and could be reused.

The researchers said that their technique is low cost, rapid, and straightforward and could be used to form lenses with different sizes and shapes. To create lenses of various sizes, the researchers used different-size droplets. To change the magnetic field or the shape of the mold, the researchers moved the magnets.

“We brought the concept of interfacial tension to the field of optics by introducing an innovative, controllable liquid mold,” said professor Lei Li. “This novel process allowed us to regulate the shape of a magnetic drop and to create lenses without having to fabricate expensive molds.”

The research was published in Applied Physics Letters (https://doi.org/10.1063/1.5090511).