First developed in 1960, lasers have been rising in popularity over the last few years. The global laser technology market is projected to grow to $35.4 bln by 2032. This growth is driven by the rising demand for lasers across different sectors, including communication, defense, science, security, data storage, and more.
Lasers, which are devices that emit light via optical amplification, are widely used for etching. Laser etching is a process for creating markings on the surface of a product, such as QR codes, barcodes, logos, and serial numbers. These markings contain vital information to track the source of a particular product throughout its entire life cycle, ensuring its safety and durability. Additionally, this process is used to create artwork for products.
Laser etching falls under a larger category of laser marking, which also includes laser annealing—a process that heats the material—and laser engraving, which involves vaporizing the material. Being highly versatile, the laser can etch most metals.
So, how does this work?
To create a mark, the laser beam emits a high amount of energy to a concentrated area, melting the material”s surface. As the surface expands and cools, it forms the desired mark. Unlike other processes that merely change the color or texture of the surface, laser etching actually alters the surface, creating a raised or sunken area with a rougher texture.
Thus, by altering the surface of a material with the help of a laser, different permanent designs and patterns are created.
Different types of lasers used for etching include fiber, CO2, crystal, diode lasers, and diode-pumped solid-state lasers.
This method of creating marks on a material offers benefits such as speed and extensive customization. It is also a non-contact method that does not cause chemical reactions or create mechanical stresses and produces superior-quality marks. Laser etching can also withstand non-abrasive treatments such as powder coating.
Moreover, laser etching can be used on a wide variety of materials such as wood, leather, plastics, glass, ceramics, natural stone, and semiconductors. It is also effective on almost all metals, including aluminum, anodized aluminum, lead, magnesium, steel, zinc, copper, brass, and titanium can be etched. Basically, almost any type of material can be laser etched.
However, laser etching is not without its issues, such as high upfront costs for machines. Additionally, the marks can wear out in abrasive environments, such as those exposed to sandblasting.
Despite these challenges, the benefits of laser etching far outweigh its drawbacks, making it recommended for most marking applications. Laser etching is widely used across many industries for its versatility, efficiency, and precision, including automotive, electronics, packing, and defense metal fabrication, jewelry, art, and medical devices.
Another interesting application of laser etching is data storage. More than a decade ago, Hitachi talked about preserving information for hundreds of million years by laser-encoding it in slabs of quartz glass. However, the technique didn’t tackle the problem of managing the vast amount of data.
A few years ago, Peter Kazansky, a professor at the Optoelectronics Research Centre at the University of Southampton, stored 500 terabytes of data on a small glass disc via laser etching.
Modification of Polysulfide Surfaces with Low-Power Lasers
Given the vast benefits of laser etching, researchers and scientists are always looking for ways to improve the technology and find new applications. Recently, researchers from Flinders University discovered that an inexpensive, light-responsive sulfur-derived polymer is receptive to low-power, visible-light lasers.
Typically, in order to alter the surfaces of polymers, which consist of very large molecules, we need lasers that emit very high power. Using high-power lasers, high-tech electronics, biomedical products, and data storage components can be produced. However, with the latest discovery, we can see more affordable and safer production methods.
According to research associate and co-author Dr Lynn Lisboa:
“The impact of this discovery extends far beyond the laboratory, with potential use in biomedical devices, electronics, information storage, microfluidics, and many other functional material applications.”
Published in Angewandte Chemie International Edition, the study notes the importance of modifying polymer surfaces with laser light in supporting advances in various fields while pointing out that such alterations usually need expensive, high-power lasers, which further require special tools and facilities to reduce the risk of exposure to a dangerous level of radiation. Then, there are polymer systems themselves that tend to be intricate and expensive to develop so that lasers can alter them with ease.
As such, polymers that are easily accessible and react when exposed to low levels of radiation are needed, as that would mean simpler, safer, and more economical laser systems.
The discovery of inexpensive and rapidly alterable sulfur copolymers using lasers that deliver low-power visible and invisible infrared light addresses these needs. To create sulfur copolymers, the researchers utilized the elemental sulfur (S) and either cyclopentadiene or dicyclopentadiene.
Then, using a suite of low-power wave lasers with wavelengths of 532, 638, and 786 nm, the team was able to modify the polymers’ surfaces. These modifications include etching through ablation or controlled swelling.
The study then utilized polymer systems’ modification through laser and facile synthesis in two applications—erasable information storage and direct laser lithography. The high sulfur content of these polymers transmits a variety of chemical, physical, and optical properties, enabling diverse applications in energy storage, thermal imaging optics, and metal binding.
Then, there are the S−S bonds that can be broken and reformed, enabling restoration and usage. S−S bonds’ liability in sulfur copolymers is what led to the study’s discoveries. In particular, researchers noted that the copolymer’s surface was visibly altered just after having an exposure of less than 1 second to a 690 nm, 1.10 mW diode laser. The study stated:
“Given the low power of the laser and brief exposure times, this rapid polymer modification was a surprise.”
Laser Modifications Enable Erasable Information Storage
The chemistry journal where the study was published also featured a laser-etched version of the famous Mona Lisa etching along with the printing of a micro-braille, which was smaller than even the round head of a pin.
Funded by the Australian Research Council, Flinders Microscopy and Microanalysis, ANFF-SA, and Microscopy Australia, the study highlights a discovery that could pave the way for the use of more sustainable materials. Specifically, the study utilized a polymer made from the low-cost industrial byproduct elemental sulfur. Moreover, this method can mitigate the need for expensive, specialized equipment. It is important to note, however, that high-power lasers carry the risk of hazardous radiation.
The discovery was made during a routine analysis of a polymer invented two years ago at the Chalker Lab by PhD candidate Samuel Tonkin and Professor of Chemistry Justin Chalke from the Flinders University Institute for NanoScale Science and Engineering.
The novel polymer was found to be modified right when the laser light touched its surface. This, the study co-author and Flinders University researcher Dr Christopher Gibson said, was an “unusual response” that hasn’t been observed before on any other common polymers. He said:
“We immediately realized that this phenomenon might be useful in a number of applications, so we built a research project around the discovery.”
Calling this an exciting development, Abigail Mann, a Flinders College of Science and Engineering PhD candidate, said that by using novel techniques to fabricate structures of micrometer and smaller scales for sulfur-based materials, they “hope to inspire a broad range of real-world applications in our lab and beyond.”
This discovery provides a new way of generating precise patterns on the polymer surface. Such capability has potential applications in biomedical devices with patterned surfaces, novel methods for using polymers in data storage, and alternative approaches to manufacturing nanoscale devices for microfluidics, sensors, and electronics.
In a practical demonstration of its potential for erasable information storage, the study showcased the ability to encode a message in Braille. This was achieved by using a laser to create raised dots on the material, leveraging the dynamic S−S bonds and properties akin to vitrimer—a category of plastics that facilitated both the writing and erasing of the message.
To create the spelling of “secret message” in Braille, the researchers used a laser with a lower laser power setting (638 nm, 2.4 mW). The raised dots, which had a height of 3.6 μm±0.2 μm, were formed by exposing the surface of the polymer to the laser for just 1.3 seconds.
Then, the team used a higher power setting (638 nm, 5.4 mW) to create pits in the corners through ablation and material removal. Again, the laser exposure here was also 1.3 seconds.
The study found that the thermal treatment erased the lifted dots when incubated in an oven at 160 °C for 5 hours. The pits formed by ablation, meanwhile, remained intact due to the polymer permanently losing sulfur.
The process of removable information encoding, as per the study, “constitutes a new direction in photoresponsive materials, with benefits in the simplicity of the material synthesis and use of low-power lasers.”
The study further demonstrated the generation of a complex, microscale image using direct laser lithography. Using a 532 nm laser operating at 7 % power (1.3 mW), the Flinders research team generated the finer lines of the “Micro Lisa.” The microimage was about nine μm wide and two μm deep. Microns or micrometers, represented as µm, are equivalent to one-millionth of a meter.
Using a higher power laser (3.0 mW), the team then generated the wider and deeper lines of the 23 μm wide and five μm deep square frame. This direct laser lithography, as per the team, is distinctive in terms of the low cost of polymer substrates and the simplicity of the laser system.
Click here to learn how lasers might transform modern computers.
Conclusion
As we saw in this study, using low-power visible and infrared laser light, the researchers were able to modify copolymers. The modifications have been swift, with exposure times being extremely short — from milliseconds, a thousandth of a second, to a second. This timescale can be of significant advantage in various industries, especially those that require the whole prototyping and manufacturing processes to be done fast.
By controlling the wavelength, diameter, and power of the beam, the researchers were able to create raised dots, holes, pits, channels, and spikes on the polymer surface. This versatility means even complex patterns can be created, which can improve functionalities and meet specific applications.
But this is not all. Simply by heating the sample, the researchers were further able to erase the polymer swelling modifications. These capabilities are significant, as demonstrated by the team with direct laser lithography of complex images and erasable information encoding.
This study has not only provided a simple method as well as low-cost materials and laser systems that can help provide more accessible and cost-effective solutions but can also be specifically useful in encryption, data storage, and many other fields where temporary modifications are needed.
Click here to learn why lasers are set to play a pivotal role in the coming days.
