At the Mayo Clinic Glass Shop, scientific glassblowing creates glass tubing and apparatuses for cardiac, transplantation and tissue perfusion research — and more recently, to help fight the COVID-19 pandemic.
Steve Anderson is one of only two scientific glassblowers in Minnesota. As a senior scientific glassblower at Mayo Clinic, he has developed glass aneurysm models, aortic stent placement training aids and liver perfusion systems. Recently, he received a request to make nebulizers to test the fit of N95 face masks in the fight against coronavirus. It was an apparatus he’s never made before.
“They can purchase the nebulizers made of plastic, but the people doing the testing prefer the glass models,” Anderson told Medical Design and Outsourcing. “They only have a few of the glass models, which are probably quite old, so they asked me to make up 20 more for them.”
Scientific glassblowing is a form of glasswork that is used in organic chemistry, medical devices, pharmaceutical applications and research. Some of the earliest examples of scientific glassblowing include Galileo’s thermometer and Thomas Edison’s light bulb, according to the American Scientific Glassblowers Society. Today, scientific glassblowing offers highly specialized glass apparatuses for a number of applications, from training to nebulizers.
The Mayo Clinic Glass Shop goes back to the early 1900s and specializes in scientific glassblowing. It works in collaboration with clinical and research groups within the Division of Engineering at the Rochester, Minn.–based health provider. The shop has manufactured a number of glassblown apparatuses and models for research and training aids for physicians to practice endovascular skills and more.
The unique properties of glass offer benefits that medical researchers sometimes prefer over other materials like plastics.
“Glass is a real inert material, and it’s resistant to most acids,” Anderson said. “It has a low coefficient of expansion, so you can autoclave it. You can adjust the temperature of an experiment rather quickly, and it won’t break. When you’re all done, you can wash it up and reused it again, sterilize it with the autoclave and put it back into service.”
For his new nebulizer project, Anderson is reverse-engineering one of the plastic nebulizers Mayo Clinic had. He starts with a 4- to 5-ft length of glass tubing and a 4 mm diameter tube to make the spray nozzle. The main body of the nebulizer is made from a 10 in. piece of 18 mm tubing with a 32 mm bulb that has a 5 ml reservoir on one end. Then, 4 mm OD tubing is used to fabricate a small injector that has a venturi-type effect to create a mist with a scent. If a person wearing a mask can smell the scent, the seal is no good.
“I seal the venturi tube into the bottom of the 5ml reservoir. So, when they give it a burst of air, it siphons up a small amount of water with some kind of scent in it. This creates a little mist that blows into a small hood area where the person is wearing a mask. If they can smell the scent, the mask’s seal is no good,” Anderson said.
For medical devices, glassblowing offers high mechanical strength against pressure and impact. Most of the scientific glassblowing Anderson does consists of borosilicate glass, which is more commonly known by the trade name Pyrex.
Glass for scientific glassblowing has working characteristics that are much stiffer than artistic glassblowing, according to Anderson. The soft glass in artistic glassblowing has a higher coefficient of expansion than the borosilicate used, so it stays soft and pliable longer.
“They make glass with many different properties, so you can actually seal glass to different metals and alloys for glass-to-metal sealing, which is good for working in vacuum systems,” he said.
Glass tubing is made using tools such as bench burners, hand torches and lathes. To make the tubing, Anderson puts a piece of glass on a lathe with a stopper connected to a swivel with a latex blowhose that allows the glassblower to blow through. Anderson heats up the glass as he turns it in the lathe. He can then bring in the tail stack of the tube as the glass melts or softens — thickening it or pulling it out thin. He can also shape tubes into different fixtures or fittings with joints on one side and a piece on the other.
“For high precision or larger pieces, I use a lathe. Smaller pieces I’ll make by hand, sitting at a bench with my torch,” Anderson said.
Anderson has also developed perfusion tissue baths with ECG capabilities at the Mayo Clinic Glass Shop. The perfusion tissue bath was created for cardiac researchers who requested a new design because the perfusion tissue baths they were using at the time were unable to simultaneously record multiple cardiac parameters without causing damage to the myocardium. The glass version allows for simultaneous automatic recording of the electrocardiographic, biochemical, hemodynamic and electrophysiological changes from a perfused heart in temperature- and oxygenation-controlled environments.
Anderson and engineers within Mayo Clinic’s Division of Engineering have also made a liver perfusion system for transplantation research. The glass design increased the average viability of the liver cells and the average yield of cells per gram of liver tissue. Human cells that have been isolated in the perfusion system have been used to study liver cell engraftment, vaccine testing, virus traits, studying the disease mechanism of the liver and for work on creating an artificial liver.
One of the most recent scientific glassblowing projects Anderson and his colleagues completed was a training aid for aortic stent placement. The model is a glass replica of the aorta with major arterial branches that can replicate aneurysmal disease of the aorta. Mayo Clinic fellows and residents are able to practice intricate procedures without being exposed to radiation or injuring a patient.