This probably won’t come as a surprise, but vaccinating wild bats is a difficult task. It’s also an important one: many bat populations are now endangered by white-nose syndrome, a serious fungal disease that invades the skin of bats. The infection causes them to rouse frequently during hibernation, over-expending their energy reserves when they should be in torpor. 

There’s a vaccine against the fungus, but this requires painstaking capture and manual application of the medicine. It would be far better to administer vaccine to many bats at once, if it were possible to spray the vaccine onto the bats as they enter and exit their dwellings. The vaccine would then be consumed by the animals as they groom the sprayed material from their fur. Which is why the National Wildlife Health Center, a unit of the U.S. Geological Survey, recently partnered with PARC, a Xerox company, to undertake a wildlife protection project in Madison, Wisconsin. The goal is to explore the use of new spraying technologies to treat wild bats with topical vaccines.

It’s important, not just for the bats themselves; the flying mammals are also a valuable “natural pesticide,” saving farmers in the United States up to $3 billion per year in avoided pest control measures. And bats are better for the environment than pesticides!

Unfortunately, vaccines—and a wide variety of other fluids of medical and industrial interest—are notoriously hard to spray, because the delivery media stiffen as they stretch. This behavior, known as strain hardening, leads to the formation of stable filaments that resist breaking up into droplets, which makes it impossible to create uniform spray. In other words, the more you pull on them, the harder they resist breaking apart. You may have come across this behavior in a commonly encountered strain-hardening fluid: melted mozzarella.

So how to vaccinate large numbers of wild bats without capturing and inoculating them by hand? This is where PARC’s filament extension atomization (FEA) technology comes in. FEA is able to break up the fluid filaments into droplets, taking advantage of strain-hardening behavior to create a uniform mist.

Here’s how FEA works: Two high-speed rollers come together in a contact area known as a nip. As the fluid is pushed through the nip, multiple filaments are formed, stretching and thinning as they are pulled apart by the roller surfaces, before eventually breaking into fine droplets. Of course, a lot of complex engineering goes into making this actually work, but the result is a fine mist that can be captured and directed to where it’s needed. In this case an aerosol, either inhaled or absorbed through the skin, is the most scalable way to vaccinate the largest number of bats with one deployment.

The USGS-PARC team will be led by Tonie Rocke, an expert in wildlife infectious diseases and vaccinations. She explains that up to 90 percent of bat populations in Wisconsin have been depleted by white-nose syndrome in recent years, posing a serious threat to the survival of bats all over North America. The team will first deliver mock vaccines to through aerosol spraying in caves and small mines over the course of two years to maximize uptake by bats, and later, when optimized, the real vaccine will be delivered. PARC will build the prototype spray devices and help with installation and field testing; the USGS team will lead field testing to quantify the physiological responses and effects on the bats.

PARC’s atomizer breakthrough enables a broad range of new spraying applications across a variety of industries. For instance, FEA technology could be used to apply paint in a thin, controllable layer, without the need for harmful VOCs. PARC is currently working with a paint company to investigate using FEA to apply specialized coatings to aircraft. The FEA approach has also been applied to generate polymer powders for additive manufacturing and other industrial uses. There are a wide variety of consumer uses for the technology as well. For example it could be used to spray sunscreen without resorting to foul-smelling formulations that sting users’ eyes.

The flexibility and broad applicability of FEA allow us to reimagine what novel spraying techniques can accomplish today and what may be possible in the near future for a wide variety of industrial and consumer uses. For now, we are hopeful that the USGS-PARC wild bat vaccination project will have a lasting effect to cure bats of white-nose syndrome across Wisconsin and beyond.