Ceramics are hard and durable; they resist scratches better than glass and stand up to high heat better than most metals. They could protect electronic devices from challenging conditions found in space or in the human body—but their very toughness makes them hard to manipulate. Joining two ceramic slabs with an airtight seal requires heating them to about 2,000 degrees Celsius, which would typically destroy embedded electronics. Now, however, researchers have developed a welding technique that spot heats the ceramics with lasers, as described in August in Science.
Lasers have already fused glass: pulsing a specially tuned beam about a trillion times a second can melt a targeted spot. But unlike glass, a ceramic scatters this light instead of absorbing it. “When you think of a ceramic, you think of a coffee cup or a bowl,” says principal investigator Javier E. Garay, a mechanical and aerospace engineer at the University of California, San Diego. Such items are opaque because they contain tiny light-scattering pores, Garay explains. Adjusting the manufacturing process to reduce the pores' size and number, an idea pioneered by ceramic scientist Robert Coble 60 years ago, can make the material translucent or transparent.
Working with a transparent version of a common ceramic and a laser technique similar to the one used for glass, the researchers successfully welded cylindrical containers. The resulting seam was tight enough to hold a vacuum with little air leakage, qualifying it for use in harsh environments such as space. Because these ceramics do not react with living tissue, they could also encase electronic devices implanted in the human body.
“It's a major engineering achievement,” says Himanshu Jain, a materials scientist at Lehigh University, who was not involved in the new study. Although previous research has used lasers to melt ceramics, he notes, this is the first time a laser has welded ceramic pieces together. “The hardest part is to get the proof of principle,” he says. “Now, to go into detail and understand the science behind it, why it works and how it works—all those things are yet to be done.”