News and events - Tampere University of Technology

Laser writes light-emitting barcodes in the size of micrometres

A new laser-writing technique enables the formation of silver nanoclusters that can used as building blocks for light-emitting microstructures. 100,000 times smaller than the diameter of a human hair, these nanoclusters can be used in high-volume data storage and fluorescent labelling, for example.

In his dissertation, MSc Puskal Kunwar has developed a novel laser-writing technique for forming highly photostable silver nanoclusters in polymers and for writing fluorescent micropatterns. This technique utilises an inexpensive, low-power laser that significantly decreases the cost of fabrication, thus making the process more attractive for application development. As a demonstration, Kunwar has fabricated a microscale fluorescent QR code with very low laser power, corresponding to the specification of cheap laser pointers. He has also developed a technique called ‘parallel laser writing’ that significantly reduces the time required for writing these microstructures. In the process, Kunwar uses a spatial light modulator, a device widely used to pattern laser beams.

“These nanoclusters can be used in many applications such as high-resolution microscopy and lithography, high-sensitivity molecular sensing, high-volume data storage and fluorescent labelling, to name but a few. The research is therefore highly significant for the research community and society on a wider scale,” Kunwar points out.

Fluorescence microscopy images of barcode (on the left) and the TUT logo (on the right). The white scale bar is equal to 5 micrometers.

“My research enables further elaboration for reaching a better understanding of the formation mechanism, actual size, composition, structure and properties of nanoclusters. This type of study could provide answers to many intriguing questions, such as ‘How are the nanostructures formed?’ and ‘Why does the size of a matter have a significant impact on its physical, chemical, electronic and optical properties?’.”

Kunwar’s research features two main contributions: the invention of a new material system, consisting of silver-containing polymer film in which the light-emitting capabilities of the material can be tailored using laser writing. Secondly, the innovation of novel laser-writing techniques enables forming and patterning silver nanoclusters in polymer. Kunwar believes that there are boundless ways to use these nanoclusters in real-life applications.


Public defence of a doctoral dissertation on Friday, 16 September 2016

The doctoral dissertation of MSc Puskal Kunwar in the field of natural science and engineering entitled ‘Direct Laser Writing of Silver Nanoclusters in Polymer Thin Films’ will be publicly examined at the Faculty of Natural Sciences of Tampere University of Technology (TUT) in Auditorium S2 in the Sähkötalo building (address: Korkeakoulunkatu 3, 33720 Tampere, Finland) at 12 noon on Friday, 16 September 2016.

The opponent will be Professor Lionel Canioni (University of Bordeaux, France). Associate Professor Juha Toivonen from the Department of Physics at TUT will act as Chairman.


Puskal Kunwar (30) comes from Tansen, Nepal, and he works as a researcher in the Applied Optics group at the Department of Physics of TUT.

News submitted by: Tiina Leivo
Keywords: science and research, silver nanocluster, fluorescent micropattern, parallel laser writing