Ceramics have been challenging to weld together because they need extremely high temperatures to melt, exposing them to extreme temperature gradients that cause cracking. Ceramic materials are biocompatible, extremely hard, and shatter-resistant, making them ideal for biomedical implants and protective casings for electronics.
Currently there is no method to encase or seal electronic components inside ceramics because the entire assembly would need to be placed in a furnace, which would burn the electronics. The new method aims a series of short laser pulses along the interface between two ceramic parts so that heat builds up only at the interface and causes localized melting. The ultrafast pulsed laser welding works in ambient conditions and uses less than 50 watts of laser power, making it more practical than current ceramic welding methods that require heating the parts in a furnace.
With the right combination of laser parameters (exposure time, number of laser pulses, and duration of pulses) and the transparency of the ceramic material, the laser energy couples strongly to the ceramic, allowing welds to be made using low laser power at room temperature.
The ultrafast pulses were two picoseconds at the high repetition rate of one megahertz, along with a moderate total number of pulses. This maximized the melt diameter, minimized material ablation, and timed cooling for the best weld possible. By focusing the energy, temperature gradients are not set throughout the ceramic, so temperature-sensitive materials can be encased without damaging them.
The process has been used to weld small ceramic parts that are less than two centimeters in size. Future work will optimize the method for larger scales as well as for different types of materials and geometries.