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A new way to measure male fertility has been discovered by researchers at the University of Waterloo, opening the door to the development of simple, inexpensive tests for clinical and at-home use.

The research team combined expertise in sperm cell behavior and interface science to determine that the movement of healthy sperm within semen reduces the force with which droplets stick to a water-repellent surface.

The study, "Connecting Droplet Adhesion with Sperm Kinematics: A New Paradigm in Sperm Quality Monitoring," was recently in Advanced Materials Interfaces.

By measuring that force using a flexible strip known as a cantilever, researchers were able to determine if a semen droplet contained moving—and therefore healthy—sperm cells.

"Think of it like this: active, swimming sperm help the droplet let go more easily," said Dr. Sushanta Mitra, a professor of mechanical and mechatronics engineering and executive director of the Waterloo Institute for Nanotechnology. "The more active the sperm, the less the droplet sticks."

Since movement is a key indicator of the health of sperm, which must be able to swim more than 1,000 times their own body length to reach and fertilize the egg, measuring the adhesion force of semen droplets provides a clear window into fertility.

"It's similar to pulling apart two pieces of tape," said Mitra. "The stronger they stick, the more force is needed to separate them. In this case, droplets with healthier sperm require less force to pull away."

Current male fertility tests involve examining sperm activity under microscopes in laboratories. The Waterloo-led research could give fertility clinics a much cheaper, easier way to measure sperm quality and even lead to simple strip tests for at-home use.

"I was excited to see the correlation of sperm motility and droplet adhesion," said Dr. Veronika Magdanz, a professor of systems design engineering. "It is a completely new approach that opens new avenues for sperm diagnostics."

The principle at the heart of the multidisciplinary innovation—that reduced sticking force equals greater sperm movement and health—could also be applied to fertility testing in veterinary medicine and animal breeding.

Researchers will now focus on standardizing the measurement process, developing precise testing surfaces, creating a protype and conducting large-scale validation tests, as well as testing with different species.

"We are encouraged by our results, which demonstrate a clear link between sperm motility and droplet adhesion, but more development work is needed to create practical testing devices," said Mitra.

The research team also included postdoctoral fellows Sirshendu Misra and Sudip Shyam.