Scientists have used an ultrafast laser system to successfully weld optical materials such as quartz, borosilicate glass and even sapphire to metals including aluminium, titanium and stainless steel.
The new process, developed at Heriot-Watt University in Edinburgh, Scotland, could have direct applications in the aerospace, defence, optical technology and healthcare sectors.
Dissimilar materials such as glass and metal are very difficult to weld together due to their different thermal properties – the high temperatures and highly different thermal expansions involved cause the glass to shatter.
While currently equipment and products involving glass and metal are often bonded together using adhesives, these are messy to apply and the parts can gradually move over time. Outgassing – where organic chemicals from the adhesive are gradually released – can also be an issue, as it leads to reduced product lifetime.
The Heriot-Watt scientists’ process instead uses a picosecond laser to deliver ultrashort pulses of infrared light in spiral tracks along the materials, creating a weld that fuses them together (see image below).
Ultrashort laser pulses can be used to produce a spiral weld (left) at the interface between glass and metal, enabling them to be fused together (bottom middle). Image: Heriot-Watt University
Professor Duncan Hand, director of the five-university EPSRC Centre for Innovative Manufacturing in Laser-based Production Processes (CIM-Laser), based at Heriot-Watt, explained the process: ‘The parts to be welded are placed in close contact, and the laser is focused through the optical material to provide a very small and highly intense spot at the interface between the two materials – we achieved megawatt peak power over an area just a few microns across. This creates a microplasma, like a tiny ball of lightning, inside the material, surrounded by a highly-confined melt region.’
Once made, the welds were tested at temperatures between -50⁰C and 90⁰C and remained intact, proving to the scientists that they are robust enough to cope with extreme conditions.
‘Being able to weld glass and metals together will be a huge step forward in manufacturing and design flexibility,’ Professor Hand remarked.
The spiral weld can be seen clearly here at the interface between the glass and metal. Image: Heriot-Watt University
Professor Hand and his team are working with a consortium including laser firms Oxford Lasers and Coherent Scotland, as well as end-users Leonardo and Gooch & Housego, to develop a prototype for the new laser processing system and take it closer to commercialisation. Two other partners, Glass Technology Services and the Centre for Process Innovation, provide additional routes to commercialisation, including the packaging of OLED devices.
The project is funded by Innovate UK, Heriot-Watt University and contributions from additional industry partners.