Graduate student Mojtaba Falahati holds a homemade lens produced by the new magnetic droplet technique. Photo: WSU.
Graduate student Mojtaba Falahati holds a homemade lens produced by the new magnetic droplet technique. Photo: WSU.

Researchers from Washington State University and Ohio State University have developed an easy, low-cost way to make custom lenses that could help manufacturers avoid the expensive molds required for optical manufacturing.

Led by Lei Li, assistant professor in the School of Mechanical and Materials Engineering, and graduate student Mojtaba Falahati, the researchers developed a liquid mold from droplets that they can manipulate with magnets for creating lenses in a variety of shapes and sizes. They report their work in a paper in Applied Physics Letters.

High-quality lenses are increasingly used in everything from cameras to self-driving cars, and virtually all robotics, but the traditional molding and casting processes used in their manufacturing require sophisticated and expensive metal molds. So, manufacturers are mostly limited to mass producing one kind of lens.

"The molds are precisely finished and are difficult to make," said Li. "It isn't worthwhile to make a mold for low-volume production."

The researchers ran into this problem first-hand as they searched for lenses for their work developing a portable laboratory reader on a phone. They first tried to make their own lenses using 3D printing but found it difficult to control the lens shape. Then they came up with the idea of using magnets and the surface tension of liquids to create free-flowing molds.

This involved placing tiny, magnetic iron particles into liquid droplets and building a device to surround the droplets with magnets. They then poured the plastic material used in lenses over the droplet. As they applied a magnetic field, the droplet took on a conical lens shape – creating a mold for the plastic lens material.

Once they cured the plastic, it hardened and had the same optical properties and imaging quality as a commercially purchased lens. The liquid droplet remains separate and can be re-used.

The magnets can be moved to change the magnetic field, the shape of the mold and the resulting lens. The researchers also used bigger or smaller droplets to create lenses of varying sizes.

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

This story is adapted from material from Washington State University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.