Researchers may have taken the first step down that road by creating a wearable ultrasound patch — think of a Band-Aid with sonar — that provides a flexible way to see deep inside the body. Ultrasound, which maps tissues and fluids by recording how sound waves bounce off them, can help doctors examine organs for damage, diagnose cancer or even track bacteria. But most ultrasound machines aren’t portable, and the wearable ones either struggle to spot details or can be used for only short periods. The medical possibilities range wide. Stick a patch over a person’s heart, and the frequent images it takes could help predict heart attacks and blood clots potentially months before disaster hits, explains Adana Singh, a biomedical engineer at Columbia University. Placed on a COVID-19 patient, the patch — which is only about the size of a quarter — could be an easy way to catch lung problems as they develop.“This is just the beginning,” says Xuan Zhao, a mechanical engineer at MIT. His team plans to make the patch wireless and able to interface with a user’s phone, which could then show the ultrasound signals as 3-D images. “This also has a huge potential to be available for developing countries,” where limited access to hospitals can make monitoring patients difficult, Singh says. The patch costs about $100 to make. One of the researchers’ next steps will be to try to make the device cheaper. Picture a smartwatch that doesn’t just show your heart rate, but a real-time image of your heart as it beats in your chest. Researchers may have taken the first step down that road by creating a wearable ultrasound patch — think of a Band-Aid with sonar — that provides a flexible way to see deep inside the body. Ultrasound can now track bacteria in the body like sonar detects submarines.
For the first time, researchers have genetically modified microbes to form gas-filled pouches that scatter sound waves to produce ultrasound signals. When these bacteria are placed inside an animal, an ultrasound detector can pick up those signals and reveal the microbes’ location, much like sonar waves bouncing off ships at sea, explains study coauthor Mikhail Shapiro, a chemical engineer at Caltech.Repurposing ultrasound, a common tissue-imaging method, to map microbes creates “a tool that nobody thought was even conceivable,” says Olivier Couture, a medical biophysicist at the French National Center for Scientific Research in Paris, who wasn’t involved in the work.
Until now, researchers have tracked disease-fighting bacteria in the body by genetically engineering them to glow green in ultraviolet images. But that light provides only blurry views of microbes in deeper tissue — if it can be seen at all. With ultrasound, “we can go centimeters deep and still see things with a spatial precision on the order of a hundred micrometers,” Shapiro says.Shapiro and his colleagues engineered a strain of E. coli used to treat gut infection to form gas compartments, and injected these bacteria into mice’s bellies. Unlike glowing bacteria — which could only be pinpointed to somewhere in a mouse’s abdomen — ultrasound images located the gas-filled microbes in the colon. The researchers also used their ultrasound technique in mice to image Salmonella bacteria, which could be used to deliver cancer-killing drugs to tumor cells.
Bacteria that produce ultrasound signals can also be designed to help diagnose illnesses, Shapiro says. For instance, a patient could swallow bacteria engineered to create gas pockets wherever the microbes sense inflammation. A doctor could then use ultrasound to search for inflamed tissue, rather than performing a more invasive procedure like a colonoscopy.
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