Scientists have developed a baseball cap that zaps your scalp – and could reverse male balding.

Experts first created a wireless patch that can stimulate the scalp with electric pulses to encourage hair growth.

The 0.4-inch-thick plastic patch contains layers of differently charged materials that produce electricity when they come into contact and separate again.

It’s a phenomenon known as the triboelectric effect and can result in faster hair re-growth than being hooked up to a machine for several hours a day. The team, from the University of Wisconsin-Madison, tested it out on the backs of shaved lab rats and found that when they moved it caused the flexible patch to bend and stretch.

They found that this movement activated the triboelectric effect and noted faster growth than in rats who had been given minoxidil lotion – a common hair loss treatment.

Next the team, led by Xudong Wang, tested the patch on mice that were hairless because of a genetic deficiency.

They found that after nine days, 2-mm-long fur had grown on their skin under the patch compared with 0.8-inch-long hair that had grown on skin treated with minoxidil.

The density of the hair was also three times greater for the patch-treated areas.

Wang also tested the patch on his dad, who has been going bald for the past few years.

“It helped him to grow a lot of new hairs after one month,” he told New Scientist.

His team has now designed a baseball cap that encases the whole scalp in triboelectric materials.

Wang is seeking approval to test it in men in a clinical trial.

He says it shouldn’t be uncomfortable to wear because it produces very gentle electric pulses.

However, the hat will only work in men who are currently losing their hair or have recently become bald, because the skin loses its ability to generate new hair follicles after many years of baldness, he added.

It’s also unlikely to work as well when men sleep because they don’t produce as many movements to power the device.

“Small head movements during normal daily activity should be enough to power the device,” he added.

Previously, we reported on a breakthrough treatment from a team of scientists who say they have used stem cells to develop a way of making “unlimited” hair.

In groundbreaking trials, human cells were grafted on to mice cells and attached to tiny “scaffolds” to help them grow straight.

They were then placed under the skin and emerged through it.

The team is now working toward tests on humans.

Around four in 10 Brit fellas suffer some form of baldness.