Stamp-sized ultrasound stickers can see inside the body

Currently, ultrasound imaging requires bulky equipment available only in hospitals and doctor’s offices. The new devices stick to the skin and can provide continuous ultrasound imaging of internal organs for 48 hours.

The researchers, who believe their devices could eventually be cheaply available in pharmacies, applied the stickers to volunteers and showed the devices produced live, high-resolution images of major blood vessels and deeper organs such as the heart, lungs and stomach.

The stickers maintained a strong adhesion and captured changes in underlying organs as volunteers performed various activities, including sitting, standing, jogging and biking.

The current design requires connecting the stickers to instruments that translate the reflected sound waves into images. The researchers point out that even in their current form, the stickers could be applied to patients in the hospital, similar to heart-monitoring EKG stickers, to continuously image internal organs without requiring a technician to hold a probe in place for long periods of time.

If they could be made to operate wirelessly, a goal the team is currently working toward, the ultrasound stickers could be made into wearable imaging products that patients could take home from a doctor’s office or even buy at a pharmacy.

“We envision a few patches adhered to different locations on the body, and the patches would communicate with your cellphone, where AI algorithms would analyse the images on demand,” said the study’s senior author, MIT's Professor Xuanhe Zhao.

“We believe we’ve opened a new era of wearable imaging: with a few patches on your body, you could see your internal organs.”

The MIT team’s new ultrasound sticker produces higher-resolution images over a longer duration by pairing a stretchy adhesive layer with a rigid array of transducers.

“This combination enables the device to conform to the skin while maintaining the relative location of transducers to generate clearer and more precise images,” added lead author Chonghe Wang.

The device’s adhesive layer is made from two thin layers of elastomer that encapsulate a middle layer of solid hydrogel, a mostly water-based material that easily transmits sound waves and is elastic and stretchy.

“The elastomer prevents dehydration of hydrogel,” said Xiaoyu Chen, an MIT postdoc. “Only when hydrogel is highly hydrated can acoustic waves penetrate effectively and give high-resolution imaging of internal organs.”

The bottom elastomer layer is designed to stick to skin, while the top layer adheres to a rigid array of transducers that the team also designed and fabricated. The entire ultrasound sticker measures about 2 square centimetres across and is 3mm thick – about the area of a postage stamp.