A team of researchers at the University of Duisburg-Essen in Germany has used an ultrafast laser from Trumpf subsidiary Amphos to increase the speed of industrial nanoparticle production for surface treatment applications.
Bilal Gökce (third from the left), who led the Duisburg-Essen research team, accepts the Fojtik-Henglein Prize at the ANGEL conference in Lyon, France. (Image: Trumpf)
Nanoparticles are able to enhance the surface properties of many products, for example by making eyeglass lenses more scratch-resistant, house paint more moisture-repellent, and prostheses and implants more biocompatible with the human body.
Nanoparticles can be produced by firing a pulsed laser at a metal plate made of platinum, gold or silver which is submerged in a liquid such as water. This method has proved to be far too time-consuming for industrial applications, however, as each time the metal surface is struck with a laser pulse, a cavitation bubble is formed that must first collapse before further nanoparticles can be produced. The spike in energy density as the pulse hits the surface is high enough to shield the next laser pulse, preventing the ablation of new particles. The collapse of such a cavitation bubble can take up to one millisecond, thus causing a delay in the production process.
The Duisburg-Essen researchers were able to overcome this delay by using a very powerful ultrashort pulse laser system that uses a scanner to realign each pulse, allowing nanoparticles to be ablated from a different point while a previously created cavitation bubble collapses. By doing this the researchers are able to produce up to four grams of nanoparticles per hour – a yield high enough to be feasible for industrial applications.
Amphos' 500flex ultrafast laser was used by the researchers to strike metal plates in order to produce nanoparticles at an accelerated rate. (Image: Trumpf)
The laser used is a 500flex system from Amphos, a manufacturer of powerful ultrafast lasers that was previously acquired by laser manufacturer Trumpf at the start of the year. The system generates over 40 million pulses per second, each with a duration of three picoseconds. An ultrafast laser is required as in order to produce just a single gram of nanoparticles, which are each a thousand times smaller than a bacterium, the metal plate must be struck several billion times.
The scientists were awarded the Fojtik-Henglein Prize for their proof of concept at the ANGEL (Advanced Nanoparticle Generation & Excitation by Lasers in Liquids) conference in Lyon, France, earlier this month. The prize recognises ground-breaking published research into laser and nanoparticle colloids.