An egg is perfect,” says Thomas Kimme, managing director of the laser systems manufacturer Laservorm GmbH. “From the moment it emerges, it’s a sealed space that keeps nutrients inside and keeps bacteria out.” Kimme grabs a pencil and draws two rings on a piece of paper, one just barely inside the other.
“This perfect space has a double layer of protection.” The outer calcareous shell, which is approximately 0.3 millimeters thick, protects the egg against knocks and bumps. Directly behind this is the extremely thin egg membrane, which is impermeable to bacteria, fungi and similar culprits. Kimme looks up from his drawing: “Our task was to cut the shell while leaving the membrane completely intact.”
No more mess
The job was commissioned by the Dessau Vaccine Plant, now known as IDT Biologika. The pharmaceutical industry has long been aware that eggs are the perfect choice for certain applications. They have spent decades using chicken eggs as sterile nutrient containers as part of their efforts to grow viruses for attenuated vaccines, such as those used against rabies, tetanus and malaria. But first you need to get the viruses inside the egg:
“Obviously the outer calcareous shell makes this extremely tricky,” says Kimme. The standard approach has been to crack the shells manually using mechanical pneumatic methods: “But no matter how careful you are handling the tool, the result tends to be pretty messy, with lots of breakages and rejects,” says Kimme. “It really wasn’t very efficient – and it obviously goes totally against the ethical treatment of living organisms, because there are chicken embryos growing in the eggs.”
A laser dance around the egg
So Horst Kassner from the Dessau Vaccine Plant decided to find a better way to open the shell. Hoping to hit upon a sterile method, he asked LIM Laserinstitut Mittelsachsen GmbH whether there was any way of doing it with lasers. LIM brought Kimme on board as a mechanical engineer, and together they began experimenting.
Since 1994 the laser systems manufacture Laservorm GmbH develops solutions for laser welding, laser hardening, laser cladding with powder or wire filler material as well as other production processes. The laser technologies are used by customers from branches likedrive engeneering, automotive engineering and medical technology.
“Calcium carbonate is an insulator like glass or plastic. So we quickly realized that a CO2 laser would be the best choice,” Kimme explains. “The laser delivers light at a wavelength of between 9.4 and 10.6 micrometers, which is absorbed very nicely by the calcareous eggshell.”
The laser specialists carried out several rounds of tests to optimize the parameters, ultimately creating a stable industrial process that perfectly opens the eggshell in 99.9 percent of cases. “The laser only cuts the shell. And the very low amount of heat that is applied can be contained in the minimal coagulation at the beam entry point.” Once the tests were completed, Kimme and his colleagues set about building the special machine.
Opening on the fly
The result was the Laser Egg Opener, or LEO. So how does the process work in practice? First the fertilized eggs are placed in a container that passes through an airlock. This prevents any surrounding air from entering the processing chamber. At the interface between the two zones, sensors detect whether the container is full, i.e. whether all spaces contain an egg. This tells the laser if there are any unoccupied spaces that it can safely ignore. The laser cutting process itself is carried out on the fly, but without a scanner.
“A scanner isn’t capable of scanning an entire rack of eggs, so we came up with a faster method.” The egg container moves through the laser system and the laser optics track its forward motion. The laser beam is divided into four beams which are guided with millimeter precision by mirrors. This establishes the optimum opening geometry for the downstream process and means that the system always opens four eggs at once. “It’s an extremely challenging process in terms of the control technology involved,” says Kimme. “But it allows us to process 3,000 eggs an hour, which is ten times faster than using scanning optics.” The number of eggs wasted is close to zero.
We can process 3.000 eggs an hour — this is ten times faster than using scanning optics
Thomas Kimme, managing director of the laser systems manufacturer Laservorm GmbH
Once the eggs have been opened, a filter system sucks up any shell particles, and the eggs continue their journey through a second airlock. This minimizes the risk of any bacteria hitching a ride. “Our customers work with living organisms, and they are extremely sensitive to even the slightest nonconformity in the production process,” Kimme explains. “This is why it’s crucial to have such tremendously high standards of hygiene – and this was a huge challenge for us when it came to building the machine.” For example, you can only use a limited number of very high alloy stainless steels and certain plastics that are capable of withstanding the aggressive detergents used in the industry.
“We had to cut almost every screw thread ourselves.” Other pharmaceutical companies are now also showing an interest in the high-tech egg opener. “The market for this kind of application is tiny. But thanks to laser technology, we can offer something truly unique.”