Scientists develop innovative 3D printing technology to create glass microstructures using light

2024-01-23

According to a new study published in the journal Science, researchers at the University of California, Berkeley have developed a new method for 3D printing glass microstructures. This method is faster and produces objects with higher optical quality, design flexibility, and strength.

Researchers have collaborated with scientists from the University of Freiburg in Germany to expand the capabilities of their 3D printing process, Computational Axial Lithography (CAL), developed three years ago, to print finer features and print them in glass. They call this new system "micro CAL".

Glass is often the preferred material for manufacturing complex microscopic objects, including the lenses of small high-quality cameras used in smartphones and endoscopes, as well as microfluidic devices used for analyzing or processing trace amounts of liquids. However, current manufacturing methods may be slow, expensive, and have limited capabilities in meeting the growing demands of the industry.

The CAL process is fundamentally different from today's industrial 3D printing manufacturing process, which uses thin material layers to build objects. This technology may consume a lot of time and result in rough surface textures. However, CAL simultaneously performs 3D printing on the entire object. Researchers use lasers to project light patterns onto rotating photosensitive materials, establish a three-dimensional light dose, and then solidify it into the desired shape. The non layering nature of the CAL process makes smooth surfaces and complex geometric shapes possible.

This study breaks through the boundaries of CAL and demonstrates its ability to print microscale features in glass structures. "When we first published this method in 2019, CAL was able to print objects into polymers with a feature size of about one-third of a millimeter," said Hayden Taylor, a lead researcher and professor of mechanical engineering at the University of California, Berkeley.

"Now, through micro CAL, we can print objects in polymers with features as small as about 20 million parts per meter, or about a quarter the width of human hair. Moreover, we have demonstrated for the first time that this method can not only print in polymers, but also in glass, with features that can be reduced to about 50 million parts per meter."

In order to print glass, Taylor and his research team collaborated with scientists from the University of Freiburg to develop a special resin material containing glass nanoparticles surrounded by a photosensitive adhesive liquid. The digital light projection from the printer solidifies the adhesive, and then the researchers heat the printed object to remove the adhesive and fuse the particles together to form a solid object of pure glass.

Taylor said, "The key factor here is that the refractive index of the adhesive is almost the same as that of the glass, so there is almost no scattering of light when passing through the material. The CAL printing process and the materials developed by this Glassor (GmbH) are a perfect combination of each other."

The research team also conducted tests and found that glass objects printed with CAL have more stable strength than those manufactured using traditional layer based printing processes. Taylor said, "When glass objects contain more defects or cracks, or have a rough surface, they are often more prone to breakage. Therefore, compared to other layer based 3D printing processes, the ability of CAL to produce objects with smoother surfaces is a significant potential advantage."

The 3D printing method of CAL provides a new and more effective method for manufacturers of microscopic glass objects to meet the demanding requirements of customers for geometric shape, size, optical and mechanical properties. Specifically, this includes manufacturers of micro optical components, which are key components of compact cameras, virtual reality headsets, advanced microscopes, and other scientific instruments. Taylor said, "Being able to manufacture these components at a faster speed and with greater geometric degrees of freedom may bring new device functionalities or lower costs."

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