SOUTH BURLINGTON — It is 9:30 a.m. at the headquarters of Resonant Link, in an industrial park next to Ben & Jerry’s, and almost every cubicle is still empty for two reasons, explains Rachel Allard, the company’s director of marketing: Engineers tend to come in late and work late, and the company has left room for explosive growth in hiring this year, from the current 48 employees to around 80 by year’s end.
“We definitely have a little moving in to do, as you can see,” Allard says.
Resonant Link moved into its new offices last spring. The company had been headquartered in Shelburne. Fifteen months ago, it had seven employees. By the end of 2021, it had 18, including founders Aaron Stein, Phyo Aung Kyaw and Grayson Zulauf. Last year, it hired 30 additional employees.
“They are exactly what we need for the Vermont economy,” said Lauren Bass, director of LaunchVT, a Burlington business accelerator. Resonant Link was accepted as one of eight companies in the 2020 cohort of businesses at LaunchVT. The businesses receive mentoring and training and meet with investors.
“We need the next Resonant Links, we need the next Betas,” Bass said, referring to Burlington’s electric aircraft manufacturer Beta Technologies. “They have (intellectual property). They are in tech. They are creating jobs that on the low end are high-five-figure employment opportunities for Vermonters. They are attracting talent.”
Also significant, Bass said, is that Resonant Link is raising money outside Vermont.
“Those are some of the best investors out there,” Bass said. “They are market makers and they are institutional money, and that is the highest degree of validation as far as telling the public and telling the marketplace that someone has done some serious diligence because they believe this business is going to grow.”
Resonant Link’s employees are now spread out over 12 states and three countries.
“People will work on a board, circuits or something,” said Allard. “They’ll ship it overnight to a colleague in Denver. And that person can work on that same physical piece of hardware.”
Resonant Link was founded in 2017, building on its revolutionary method to send power wirelessly using coils made of layers of foil and thin film dielectric, an electrical insulator that can be polarized by an applied electrical field.
“We build the coils in a completely different way than conventional wireless chargers are built,” said Zulauf, Resonant Link’s chief executive officer. “Ours are built with alternating layers of foil like you could buy at the grocery store and then film, instead of what other people do, which is they essentially take a braided wire and wrap it in a loop.”
The technology uses one-fifth the power of other existing wireless technology, Zulauf said. It was developed by Stein and Kyaw at Professor Charles Sullivan’s lab at the Thayer School of Engineering at Dartmouth College in New Hampshire.
“Charlie had this original idea of this new type of wireless coil that was really exciting,” said Stein, Resonant Link’s chief technology officer.
That idea was the resonant link after which the company is named.
Stein, who was working on post-doctoral research at Dartmouth, worked with Kyaw to turn Sullivan’s idea into a reality in his lab. They found that the wireless coil worked five to 10 times better than other coils. They knew that by calculating a factor called Q, which measures energy stored divided by energy dissipated during the wireless transmission, essentially determining how much energy is being transmitted to the receiver instead of being dissipated, Allard explained.
“All of a sudden, we just had this mind-blowing result,” Stein said.
They took their results to conferences and found people were excited, Stein said. So they thought they should commercialize their idea. Stein wrote a grant request for the National Science Foundation to fund the company and get it off the ground. In 2018, they were awarded a grant of nearly $225,000.
“Once that was there, we had a little bit of money and a few people with big hearts and big ideas and we rode off trying to see what we could do from there,” Stein said.
Stein said that all their customers share a need to get power through something that is hard to get power through. Their medical clients need to transmit power to devices through the human body without overheating it. Their lift truck customers have to get power through the air for as many inches as possible without dissipating too much energy, because that dissipated energy would heat up objects around it and make them unsafe to touch or would make parts fail.
“What’s hard about that is you have to create large magnetic fields to pass power over that air gap,” Stein said.
The company’s technology can wirelessly power electronics from tiny 20-milliwatt medical devices to 19.2-kilowatt chargers for lift trucks.
At the company’s headquarters, Allard opened a drawer and took out the smallest charger that the company makes — a molar implant — holding it in the palm of her hand. She said she used to tell people it was the size of a fingernail, but at three millimeters in diameter, it’s actually much smaller.
Resonant Link’s client wants to make saliva tests the new blood test, Allard said. The implant, a receiver for wireless charging, is designed to sit in a retainer or on top of a tooth like a crown. It would power an attached salivary diagnostic tool, which would detect biomarkers that could help diagnose medical conditions ranging from diabetes to throat cancer.
The device could possibly be used — eventually — to power electronics that control seizures in patients with epilepsy, Allard said. In such a case, the transmitter for the charger could be in a pillow and would recharge the implanted device while the patient sleeps, she said, or it could be in a headband or a cap.
The biggest medical device charger the company is developing is for a left ventricular assist device, a device that pumps the heart that is one-half to one-fifth as big as existing chargers, she said. The charger could be worn in a vest.
Wireless chargers for medical devices eliminate the need for surgery to replace implanted batteries and the need for wires that lead out of the body to an external charger. Besides being cumbersome, wires can lead to infections, according to Allard.
Resonant Link’s chargers for medical devices work from four to six centimeters away, Allard said.
“If you think about something that’s in your heart, you could wear the charger essentially in what would be your breast pocket,” she said. “Pretty much the possibilities are endless.”
She noted that in the past, materials for implanted receivers have been limited because they must be biocompatible so that the body does not reject them or overheat.
Allard said Resonant Link’s chargers for medical devices meet Food and Drug Administration requirements that prohibit medical devices from heating body tissue by more than 3.6 degrees Fahrenheit.
The company’s medical chargers are currently being tested on animals. After human trials, Zulauf said he expects the first FDA approval next year.
Resonant Link will not reveal its customers, but Zulauf said it is working with 12 medical-device makers. Allard said the company is also working with a big smartphone manufacturer. She said Resonant Link hopes to have the smartphone charger on store shelves by the end of this year, in time for the holidays.
Smartphone wireless chargers are already available on the market. One thing that makes Resonant Link different, Allard said, is that its chargers are more flexible.
“We’ve all had those frustrations with wireless chargers where you have to get it exactly in one spot to get it work,” Allard said. “Our chargers have to work with how people live and operate.”
Resonant Link’s smartphone charger, Allard said, works twice as far away from the phone as any competitor’s. It is also faster, she said. The electronics are constantly monitoring how much power is being transmitted so the maximum power is being sent at any given time, but not so much as to overcharge, which ruins batteries over time, she said.
“So these are constantly saying, ‘How much power are you receiving, battery? OK, great. I have to adjust a little,’” she said.
More than a billion electronic devices, most of them smartphones, have been shipped with wireless charging built in, said Zulauf. The charger that Resonant Link plans to introduce later this year can just be dropped into those phones, he said. The company’s charger will cost the same as existing coils, he said.
“When you put our coil in the phone, you can wirelessly charge that phone almost three times faster than you can today,” Zulauf said.
Customers need to be persuaded that wireless power can be fast enough, small enough, light enough and inexpensive enough to make it worth their while to incorporate it, Zulauf said.
“So people are already convinced of what wireless power can do for them,” he said. “They’ve just been waiting for a company that can deliver on the promise of wireless power.”
Existing wireless lift truck chargers, Allard said, require that the lift truck be parked within an inch or two of the charger. Lift trucks are similar to forklifts, but have a smaller turning radius that allows them to operate in tighter spaces in warehouses.
“Have you ever tried to park a lift truck within an inch or two of a base station?” she asked. “We wanted to make it as easy to use by not having to park perfectly.”
Resonant Link’s base station, which contains one of the power coils for recharging lift trucks, can be as far away as 10 feet from the power electronics in the transmitter, explained Skyler Cornell, an electrical engineer who has been working on the rechargers. The power electronics regulate how much power is sent. The transmitter that wirelessly sends a charge to a receiver on the truck can be as far away as 10 inches. The chargers can recharge lead-acid as well as lithium-ion batteries. The system works with both manually operated and autonomous vehicles, Allard said.
When Cornell demonstrated the charging sequence, the charger jumped from zero to 400 amps in less than a second.
“No one’s been able to do 400 amps yet, so that level of power is pretty key for speed of charge,” Allard said. “Essentially, they’re correlated.”
Cornell explained that Resonant Link’s wireless lift truck charger reaches 90% efficiency, meaning that 90% of the energy transmitted wirelessly is received.
Other wireless chargers for lift trucks exist on the market, Allard said, but achieve only 40% to 50% efficiency.
Efficiency influences how fast you can recharge a lift truck, Allard said.
“Every minute counts in a warehouse,” she said.
Zulauf said Resonant Link’s chargers can recharge a lift truck two to four times faster than any other wireless charger on the market.
When an object such as a wrench is placed between the transmitter and receiver, the charger shuts off, as Allard showed in a demonstration. A person would not be injured by getting between the two, she said, but an object could heat up to the point where it could burn someone trying to pick it up.
“Warehouses are super-chaotic environments,” said Allard.
If someone touches the battery on the lift truck as it is recharging, Allard said, it will feel warm, but not so it can harm the person.
The company expects to ship the initial production units of its lift truck chargers to a limited number of customers for testing in March, Allard said, before it begins producing them in volume later this year.
“Resonant Link has the opportunity to revolutionize power and energy and how that’s delivered,” Stein said. “I imagine Resonant Link will be a key player in power and energy moving forward.”
Correction: A previous caption for a photo in this story incorrectly stated how the wireless receiver would work.