Counterfeiting is a global issue and has considerable negative impacts on our society, both
economically and socially. Existing anti-counterfeiting methods such as watermarks, holograms,
and conventional laser marking are, however, becoming old-dated and ineffective.
This project aims to develop a new laser-based anti-counterfeiting technology – Superlensassisted
anti-counterfeiting Laser Dot Code marking – which can effectively prevent and
detect counterfeiting, and difficult to be copied by counterfeits. This project is timely and of
considerable potential social and economic impacts to Wales, the UK and internationally.
The key concepts behind the project include: (1) Using DotCode scheme in laser marking to
replace TEXT or other 2D code schemes (e.g QR code) for enhanced security; (2) integrating
particle superlens array into laser dotcode marking process to reduce laser focus spot size
from microscale to nanoscale. Such nanofeature-decorated DotCode marking is unique and
hardly to be copied.
Experimentally, we first performed direct laser marking of dotcode on stainless and glass
surface without particle superlens by using UV and femtosecond (FS) lasers. Advantages of
DotCode scheme over other 2D codes were demonstrated, including higher manufacturing
speed, better scalability, and readability. It is also shown that FS laser has clear advantages
over UV lasers in DotCode marking in terms of marking quality and feature size. However,
driven by the commercial needs on low-cost solution, the superlens-assisted marking was
explored using UV laser only. To deposit a large-area monolayer of microsphere array on
glass surface, three different techniques were tried, including drop-casting, spin-coating and
Modified Langmuir-Schaefer (MLS) techniques. The MLS technique was chosen for the
project due to its ability to generate required large-area monolayer particle arrays. A group of
different UV laser fluences were then tested, with the aim to find best laser parameter window
for the marking process. After this, the readout of laser-marked nano DotCode were tried
with Scanner App. The laser-marked nano Dot Codes are completely invisible to human eyes
and can only be revealed by microscopic imaging followed by image processing. Theoretical
calculation of particle superlens focusing was also carried out to support the experiments.
As a result, the proposed technique successfully demonstrates its unique ability in protecting the
information being counterfeited by others.