Eesha Khare, a high-school pupil from San Jose, California, has created a gadget which fully charges a mobile within 20-30 seconds.

The device, called a supercapacitor, small enough to fit into a phone, could mean an end to ever running low on battery power.

The invention was presented at one of the world's most prestigious science fairs this week, where Khare won a prize of £33,000.

The 18-year-old said the money would go toward funding her studies, as she was recently offered a place at Harvard.

"With this money I will be able to pay for my college and also work on making scientific advancements," said Khare.

However, big tech companies such as Google have approached Khare about her invention.

The teenager could earn a fortune which could be worth millions.

Khare said she was inspired to create the gadget after becoming frustrated with running low on battery power. "My cellphone battery always dies," she told NBC news.

Supercapacitors are storage devices that charge up very quickly and capable of dispensing 10,000 recharge cycles, which is nearly 10 times the performance of conventional batteries.

However, they are not widely used because they store less energy than normal batteries.

"The supercapacitor I have developed uses a special nanostructure, which allows for a lot greater energy per unit volume," she said during the Intel International Science and Engineering Fair in Phoenix, Arizona.

During the demo, Khare showed off how it could power an LED light. But in the future, the device could easily be used in roll-up phones or even car batteries.

"It is also flexible, so it can be used in rollup displays and clothing and fabric," Khare added. "It has a lot of different applications and advantages over batteries in that sense."

Tech companies have been searching for improving battery life of mobile phones, as batteries are one area of the device that has not kept up with other technological advances.