Even for scuba and snorkeling enthusiasts, the plunge into open water can be dislocating. Divers frequently swim with limited visibility, which can become a safety hazard for teams trying to find each other in an emergency. Yet even though many dive with smartwatches designed to go to depths of over 100 feet, accurately locating mobile devices underwater has confounded researchers.

Now, a team at the 91探花 has developed the first underwater 3D-positioning app for smart devices. When at least three divers are within about 98 feet (30 meters) of each other, their devices鈥� existing speakers and microphones contact each other, and the app tracks each user鈥檚 location relative to the leader. This range can extend with more divers, if each is within 98 feet of another diver. The team will present in September at the in New York City.

鈥淢obile devices today can work nearly anywhere on Earth. You can be in a forest or on a plane and still get internet connectivity,鈥� said lead author , a 91探花doctoral student in the Paul G. Allen School of Computer Science & Engineering. 鈥淏ut the one place where we still hadn鈥檛 made mobile devices work was underwater. It鈥檚 kind of the final frontier.鈥�

Above water, GPS relies on a vast satellite network to locate mobile devices with radio signals. Underwater, these signals quickly fade. Sound, though, travels faster and farther in water than it does in air. Previous underwater positioning systems have relied on strategically placed buoys, but these systems are expensive and cumbersome to deploy, leading many divers to do without.

The 91探花team found that such buoys aren鈥檛 necessary. With the app, if the dive leader has at least one other diver visible, the group鈥檚 devices can send acoustic signals to each other through their microphones and speakers and use the timestamps to estimate each diver鈥檚 distance. Based on these distances, the app can estimate the group鈥檚 formation and each diver鈥檚 location. If a device also tracks depth, as sport monitors like the Apple Watch Ultra or the Garmin Descent do, the system can locate divers in 3D.

The app needs at least three devices in its network to function, and its accuracy improves as more devices are added. When tested with four to five devices in local lakes and a pool, the app estimated locations with an average error of about 5 feet (1.6 meters) 鈥� close enough for divers to see each other in most environments. To get actual GPS coordinates, instead of tracking locations relative to the dive leader, the leader needs to be wirelessly connected to a surface device on a boat with GPS capabilities.

The study builds on a , which allows divers to send messages to each other underwater.

鈥淭his and AquaApp can be used together,鈥� said author , a 91探花doctoral student in the Allen School. 鈥淔or example, if the dive leader finds someone going the wrong way, the leader can send an alert: 鈥楬ey, you鈥檙e going out of range. You need to come back.鈥� Or if a diver is running out of gas, an SOS can let the team find the person quickly even in murky water.鈥�

, a professor in the Allen School, is a senior author on this paper. This research was funded by grants from the Gordon and Betty Moore Foundation and National Science Foundation.

For more information, contact underwaterGPS@cs.washington.edu.

Newborns across the United States are . This test is important because it helps families better understand their child’s health, but it’s often not accessible to children in other countries because the screening device is expensive.

A team led by researchers at the 91探花 has created a new hearing screening system that uses a smartphone and low-cost earbuds instead. The team tested this device with 114 patients, including 52 babies up to 6 months old. The researchers also tested the device on pediatric patients with known hearing loss. Their tool performed as well as the commercial device, and it correctly identified all patients with hearing loss.

The team Oct. 31 in Nature Biomedical Engineering.

“There is a huge amount of health inequity in the world. I grew up in a country where there was no hearing screening available, in part because the screening device itself is pretty expensive,” said senior author , a 91探花professor in the Paul G. Allen School of Computer Science & Engineering. “The project here is to leverage the ubiquity of mobile devices people across the world already have 鈥� smartphones and $2 to $3 earbuds 鈥� to make newborn hearing screening something that’s accessible to all without sacrificing quality.”

Because babies can’t tell doctors whether they can hear a given sound, these tests rely on the mechanics of the ear.

“When an external sound is played, hair cells in the inner ear move and vibrate. The result is a very quiet sound that our instruments can pick up,” said co-author , an associate professor of otolaryngology-head and neck surgery at the 91探花School of Medicine who practices at “This screening is very sensitive, meaning that if there is a concern about a patient’s hearing, they will be referred for a more thorough evaluation with a specialist.”

For the test, doctors send two different tones into the ear at the same time. Based on those tones, the hair cells in the ear vibrate and create a third tone, which is what the doctors are listening for.

One reason the commercial device is expensive is that its speaker has been designed to play the two tones without any interference. The 91探花researchers found that they could use affordable earbuds 鈥� where each earbud plays one of the two tones 鈥� instead. The earbuds are connected to a microphone in a probe that can be placed in the patient’s ear. The microphone records any sounds from the ear and sends them to a smartphone for processing.

“As you can imagine, these sounds that are coming out from the ear are very soft, and sometimes it’s hard to hear them over noise in the environment or if the patient is moving their head,” said lead author , a 91探花doctoral student in the Allen School. “We designed聽 algorithms on the phone that help us detect the signal even with all that background noise. These algorithms can run in real time on any smartphone and do not require the latest smartphone models.”

The researchers tested their device at three hearing clinics in the Puget Sound area in the state of Washington. For each test, they tested four different frequencies, which is typical for these types of hearing screenings. Participants ranged in age from a few weeks to 20 years old.

Now the team is working with collaborators to use this tool as part of a newborn hearing screening project in Kenya. The researchers teamed up with a group from the 91探花global health department, the University of Nairobi and the Kenya Ministry of Health to create the project “Toward Universal Newborn and Early Childhood Hearing Screening in Kenya,” or .

“Right now, this is a prototype that we created. The next challenge is really scaling this up and then working with local experts in each country who are the most familiar with the particular challenges in each situation,” Chan said. “We have an opportunity to really have an impact on global health, especially for newborn hearing. I think it’s pretty gratifying to know that the research we do can help to directly solve real problems.”

Additional co-authors on this paper are , a resident in otolaryngology-head and neck surgery at the 91探花School of Medicine; , who worked on this project as a 91探花doctoral student in the electrical and computer engineering department; , a clinical research coordinator at Seattle Children’s; , a 91探花affiliate instructor in speech and hearing sciences; and an associate professor of pediatrics in the 91探花School of Medicine who practices at Seattle Children’s. This research was funded by the National Institute on Deafness and Other Communication Disorders, the Washington Research Foundation, the Seattle Children鈥檚 Research Institute, the Seattle Children’s Research Integration Hub, the Pilot Awards Support Fund Program, a Moore Inventor Fellow award and the National Science Foundation.

For more information, contact tune@cs.washington.edu.

Grant numbers: T32DC000018, 10617

Blood clots form naturally as a way to stop bleeding when someone is injured. But blood clots in patients with medical issues, such as mechanical heart valves or other heart conditions, can lead to a stroke or heart attack. That’s why millions of Americans take blood-thinning medications, such as warfarin, that make it harder for their blood to clot.

Warfarin isn’t perfect, however, and requires patients to be tested frequently to make sure their blood is in the correct range 鈥� blood that clots too easily could still lead to a stroke or a heart attack while blood that doesn’t clot can lead to extended bleeding after an injury. To be tested, patients either have to go to a clinic laboratory or use a costly at-home testing system.

Researchers at the 91探花 have developed a new blood-clotting test that uses only a single drop of blood and a smartphone vibration motor and camera. The system includes a plastic attachment that holds a tiny cup beneath the phone’s camera.

A person adds a drop of blood to the cup, which contains a small copper particle and a chemical that starts the blood-clotting process. Then the phone’s vibration motor shakes the cup while the camera monitors the movement of the particle, which slows down and then stops moving as the clot forms. The researchers showed that this method falls within the accuracy range of the standard instruments of the field.

The team Feb. 11 in Nature Communications.

“Back in the day, doctors used to manually rock tubes of blood back and forth to monitor how long it took a clot to form. This, however, requires a lot of blood, making it infeasible to use in home settings,” said senior author , 91探花professor in the Paul G. Allen School of Computer Science & Engineering. “The creative leap we make here is that we’re showing that by using the vibration motor on a smartphone, our algorithms can do the same thing, except with a single drop of blood. And we get accuracy similar to the best commercially available techniques.”

Doctors can rank blood-clotting ability using two numbers:

• the time it takes for the clot to form, what’s known as the “prothrombin time” or PT
• a ratio calculated from the PT that allows doctors to more easily compare results between different tests or laboratories, called the “international normalized ratio” or INR

“Most people taking this medication are taking it for life. But this is not a set-and-forget type of thing 鈥� in the U.S., most people are only in what we call the ‘desirable range’ of PT/INR levels about 64% of the time,” said co-author , assistant professor of anesthesiology and pain medicine in the 91探花School of Medicine. “This number is even lower 鈥� only about 40% of the time 鈥� in countries such as India or Uganda where there is less frequent testing. How can we make this better? We need to make it easier for people to test more frequently and take ownership of their health care.”

Patients who can monitor their PT/INR levels from home would only need to go to see a clinician if the test suggested they were outside of that desirable range, Michaelsen said.

The researchers wanted an inexpensive device that could work similarly to how at-home blood sugar monitors work for people with diabetes: A person can prick their finger and test a drop of blood.

“We started by vibrating a single drop of blood and trying to monitor waves on the surface,” said lead author , a 91探花doctoral student in the Allen School. “But that was really challenging with such a small amount of blood.”

The team added a small copper particle because its motion was so much more reliable to track.

“As the blood clots, it forms a network that tightens. And in that process, the particle goes from happily bouncing around to no longer moving,” Michaelsen said.

To calculate PT and INR, the phone collects two time stamps: first when the user inserts the blood and second when the particle stops moving.

“For the first time stamp, we’re looking for when the user inserts a capillary tube containing the sample in the frame,” Chan said. “For the end of the measurement, we look directly at the interior of the cup so that the only movement within those frames is the copper particle. The particle stops moving abruptly because blood clots very quickly, and you can observe that difference between frames. From there we can calculate the PT, and this can be mapped to INR.”

The researchers tested this method on three different types of blood samples. As a proof of concept, the team started with plasma, a component of blood that is transparent and therefore easier to test. The researchers tested plasma from 140 anonymized patients at the 91探花 Medical Center. The team also examined plasma from 79 patients with known blood-clotting issues. For both these conditions, the test had results that were similar to commercially available tests.

To mimic what a patient at home would experience, the team then tested whole blood from 80 anonymized patients at both Harborview and the 91探花 medical centers. This test also yielded results that were in the accuracy range of commercial tests.

This device is still in a proof-of-concept stage. The researchers have publicly and are exploring commercialization opportunities as well as further testing. For example, currently all these tests have been done in the lab. The next step is to work with patients to test this system at home. The researchers also want to see how the system fares in more resource-limited areas and countries.

“Almost every smartphone from the past decade has a vibration motor and a camera. This means that almost everyone who has a phone can use this. All you need is a simple plastic attachment, no additional electronics of any kind,” Gollakota said. “This is the best of all worlds 鈥� it’s basically the holy grail of PT/INR testing. It makes it frugal and accessible to millions of people, even where resources are very limited.”

Additional co-authors on this paper are Joanne Estergreen, clinical laboratory supervisor in the 91探花School of Medicine’s laboratory medicine and pathology department, and , professor of laboratory medicine and pathology in the 91探花School of Medicine. This research was funded by a Moore Foundation fellowship.

For more information, contact bloodclot@cs.washington.edu.