Vaccines save millions of lives each year, but the way they’re manufactured and distributed has drawbacks. Making large batches in a factory means doses need to travel long distances. And that often presents issues with cold-storage in places with patchy electricity and/or extreme weather.

That’s why engineers at the University of Washington have been working on a less-centralized model, where vaccines potentially could be made on-demand and on-site. The research is still at an early stage. But it could eventually lead to single-dose patches that health workers make up when needed.

We’ve been thinking about making vaccines right when and where we need them.

“We’ve been thinking about how we can we disrupt the typical approach to vaccine production,” says François Baneyx, the professor of chemical engineering who leads the project. “Rather than producing the vaccines in a centralized facility and sending them refrigerated or frozen to different locations, we’ve been thinking about making them right when and where we need them.”

To make a vaccine, you harvest a pathogen, or engineer a certain type of protein. Through several stages of refinement, you can then create an antigen that is injected into the body to produce an immune response. The vaccine poses as a pathogen allowing the body to develop antibodies.

Baneyx’s team developed nano-particles made from a protein that impersonates a pathogen and that binds to calcium phosphate. When the team injected mice with the particles, they developed a particular type of T-cell that confers long-lasting immunity. “We’re pretty excited about it, because inducing these types of immune responses is hard,” says Baneyx. “Some pathogens are very hard to deal with, and if you could have these specific type of T-cells, this would be more effective in fighting disease.”

The idea is yet to be tested on humans, and would require a large, expensive series of trials before it reaches any kind of market. But the technique could make it easier to mix up a vaccine on-site, for example through a paper microfluidic device that channels very small amounts of substance together. Health workers might mix the protein, which would be in freeze-dried or dehydrated form, together with calcium phosphate using a little water. The actual vaccine might be in the form of a patch you’d slap on someone’s arm.

Baneyx, who is originally from France, received grants for the research from the Bill and Melinda Gates Foundation and the National Institutes for Health. He’s now looking for a drug company–or similar deep-pocketed entity–to take the concept forward.