Sam Altman-backed Merge Labs has a new competitor in the race to build a brain-computer interface powered by ultrasound. Bridge Neurotech is launching with $13.5 million in funding, including from venture firm General Catalyst, which has also backed major tech companies such as Anduril, Anthropic, Airbnb, and Stripe.
The company is the latest in a growing field of startups that aim to translate signals from the brain into useful actions. Elon Musk’s Neuralink, plus Synchron, Paradromics, and Precision Neuroscience are all working on brain-computer interfaces to help people who have lost the ability to move or speak.
These approaches all require surgery of some kind, which is why Bridge founder and CEO Will Biederman says he struck out on his own. “It fundamentally comes down to a difference in vision,” he says.
Biederman developed the chip Neuralink licensed to use in its first devices as part of his PhD work, but his goal with Bridge is to build a wearable device that could be used by far more people than a brain implant. Only 100 or so people around the world have received an implanted brain-computer interface as part of clinical trials, including at least 21 volunteers who have gotten Neuralink’s device.
“The risks of neurosurgery really cannot be minimized or dismissed, and so the level of safety and benefit that these devices must deliver really is quite high,” Biederman says. “Nobody really wants a hole in their head.”
But wearable brain-computer interfaces have suffered from poor signal quality. Bone and skin weaken electrical signals before they reach external sensors, which affects the performance of a device. It’s why most companies are recording electrical impulses directly from neurons in the brain. Neuralink and others have shown that these electrical systems can allow paralyzed people the ability to control electronic devices, move robotic arms, and communicate in real time with just their thoughts.
Bridge Neurotech thinks ultrasound offers an alternative to current implants and external sensors. Ultrasound uses high-frequency sound waves to bounce off moving red blood cells and measure the speed and direction of blood flow. In the brain, fluctuations in blood flow closely follow neural activity.
Both Bridge Neurotech and Merge Labs have ties to Arbor Neuroscience, which was previously known as Forest Neurotech, a nonprofit founded in 2023 by Biederman and fellow researchers Sumner Norman and Tyson Aflalo to pursue “work that is too integrated and long-horizon for a single academic lab, and too early for a company.” The organization built an instrument that uses ultrasound to image brain function that is in trials in the UK.
Merge Labs spun out of Forest Neurotech in January, with Norman and Aflalo among the company’s cofounders, which also include Altman, researcher Mikhail Shapiro, and tech entrepreneurs Alex Blania and Sandro Herbig.
Maryam Shanechi, a neuroengineer at the University of Southern California, says because ultrasound measures brain activity indirectly from blood instead of directly from neurons, there is a natural delay of a few seconds between when neurons fire and the subsequent change in blood flow and volume.
“It captures a slower variation in neural activity,” Shanechi says. “That’s fine for a lot of applications, but it depends what you want to build.”
For real-time, fast-paced tasks such as moving a robotic limb instantly or rapid typing, this lag time could pose a challenge for ultrasound-based brain-computer interfaces. Bridge is planning to use predictive AI models to cut down on that lag time and boost the performance of its interface. Biederman says the company is interested in pursuing both consumer and medical applications but didn’t comment on specific plans.
The company is starting its first clinical study in volunteers in Redwood City, California. It’s an observational study, with no treatments or diagnoses involved, in which a small ultrasound probe will be placed on the side of the head of healthy adults, as well as those who have undergone skull surgery. Bridge’s probes, which use semiconductor silicon chips made by the portable ultrasound company Butterfly Network, will record brain activity while participants listen, watch, move, and speak.
Bridge isn’t releasing images of its device yet, but Biederman says it is “something close to headphones” that will sit on the temporal window, which is located slightly above the ear. As the thinnest part of the skull, “it’s the easiest place to image through,” Biederman says. That’s relevant for ultrasound, because bone scatters and absorbs sound, which presents technical challenges for imaging noninvasively through the skull.
In a 2024 study, researchers from Caltech and the University of Southern California demonstrated that an ultrasound-based brain-computer interface could read and decode human brain activity, but it required a portion of the skull to be removed and replaced with a “window” through which ultrasound waves can pass. That is one of the biggest technical hurdles that Bridge will have to address.
“My vision is focused on noninvasive interfaces,” Biederman says. “I think that’s where the biggest opportunity to help people is.”
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