Wireless charging startup uBeam has had a rollercoaster existence. University of Pennsylvania student Meredith Perry founded the company in a garage in 2011 and raised $26 million in funding from investors including Marissa Mayer, Marc Andreessen, and Mark Cuban, who referred to the concept as a "zillion-dollar idea." The company's sound wave-based tech remained secretive. Several investors admitted they'd never actually seen it in action, which fueled suspicion among industry watchers that it might not live up to Perry's promises.

All the while, Perry stood by her invention. "We've proved out the technology," she said at a conference in May 2016, "and we are on our way to deploying the product to the world."

Then, the company's former VP of engineering wrote a series of blog posts accusing the company, essentially, of being a fraud. Paul Reynolds, who has 20 years of experience with ultrasound, wrote last year that the company had overstated its technology's capabilities and wasn't close to delivering a working prototype.

This week, uBeam finally unveiled its technology. The company demonstrated its device for USA Today, according to a report published Thursday, and it worked almost as advertised. With no cables, the company's transmitter was able to charge a phone in a reporter's hand about four feet away.

The transmitter, a large white box that sits in the middle of a room or can be mounted on the ceiling, emits high frequency sound waves that aren't detectable to the human ear. Those waves are converted into power once they reach a phone, tablet, or other device enclosed in a uBeam case.

There are major limitations, though: The waves can't pass through walls, people, or other objects, like a pair of jeans. 

The company's transmitter can charge several phones at once, so long as they're held at within a 45-degree angle in either direction with respect to the transmitter. The device to be charged must be within about 10 feet. The goal is to eventually to be able to charge devices while people walk freely around a room of a cafe, so commercialization will likely require shrinking the size and cost of the transmitters and improving their efficiency.

In February, Perry showed off the tech's charging capabilities at the Upfront Summit in Los Angeles, though from a distance. This time around, she gave a hands-on demonstration--and beforehand, took the reporter to a T-Mobile store to buy a new phone to prove it wasn't rigged.

While uBeam still has a lot of development work before it can produce a marketable product, the demo may help the startup get past the intense skepticism it faced just a year ago. Perry wouldn't make any predictions about when it might commercialize its technology, but USA Today reports that it's still at least a year away.

Perry was frank about how the criticism has affected her. "As a first-time founder and as a scientist, to have people question your integrity is horrible," she told the publication. "It was extremely painful."

"In that same week that all that stuff was being said about me, that I was a fraud, we had these big technological breakthroughs," she said. "So I just tried to focus on my team, to keep them going. So we could prove everybody wrong."

The Santa Monica-based company currently has 30 employees. There's a lot at stake: According to Allied Market Research, the market for wireless charging will be $37.2 billion by 2022.

Correction: An earlier version of this article misstated the transmitter's tracking capabilities and the eventual goal the company would like to reach with its wireless charging technology. The company uses a vision system within the transmitter to track devices, not optical lasers. UBeam aims to eventually integrate the technology into phone cases so that they can charge freely in open spaces. A phone would not be able to recharge from inside a person's pocket, as previously stated.