There's much more to the orange than juice for breakfast, according to researchers from the University of Central Florida. Engineering Assistant Professor Andrew K. Dickerson and graduate student Nicholas M. Smith studied the complex layers of the orange peel to better understand how they work together to create a microjet when the fruit is squeezed.
The pith, the white spongy layer just below the hard outer layer, contains microscopic oil reservoirs. It protects the fruit inside by absorbing impact, but the researchers discovered that when the fruit is squeezed hard enough, the pith pushes up, creating a tiny opening in the outer skin. This causes the oil to spray at an impressive 22 mph on average with acceleration of 5,000 Gs, or 1,000 times the force felt by astronauts being launched into space.
"There are several potential applications," Smith said. "For example, for asthmatics, you could have a small slice of material which would aerosolize emergency medication that you currently find in expensive, multi-use inhalers. This approach may be less expensive and biodegradable."
Dickerson and Smith believe the dynamics would work for various types of liquids and envision other potential uses as well.
"Imagine a self-diagnosing bridge," Dickerson said. "It would have an orange-like skin layer and when you were approaching material failure, you would get a preventative warning, a color change perhaps."
Much of Dickerson's work involves looking to nature for engineering solutions.
"We study natural systems to mathematically characterize how creation works, and despite the ubiquity of citrus-fruit consumption, these jets had not been previously studied," Dickerson said. "Nature is our greatest inspiration for tackling real-world problems."
The team's findings are published in Proceedings from the National Academy of Sciences.