The technician squirts a large amount of cold, greenish gel over your chest, then picks up a device that looks like a barcode scanner and starts slathering the gel around with it. On the screen next to you, shifting grey shapes resolve into a ghostly image of your heart beating. The whole thing takes 30 minutes, after which the technician hands you a paper towel to wipe up the gel. You’ve just had an ultrasound.
Now imagine taking that experience and shrinking it down to a centimeter-wide sticker you can attach to any part of your body. Instead of having to go to a hospital and lie down, you can go about your day, exercising, eating, and working. Instead of 30 minutes, the device images your internal organs continuously for 48 hours. You don’t need a technician, and you don’t need to be covered in gel.
The Zhao Lab at the Massachusetts Institute of Technology has developed exactly this. Their new invention is a bioadhesive ultrasound (BAUS) device that could revolutionize medical imaging technology. We spoke to Xuanhe Zhao, head of the Zhao Lab, about the invention and its potential applications.
A professor of mechanical engineering at MIT, Zhao has long worked on solving medical problems using hydrogels. Hydrogels are strange little polymers; highly absorbent, they nonetheless retain their shape and structural integrity because of their dense network of chemical bonds. The Zhao Lab has developed a number of hydrogel-based innovations, including quick-sealing tape that could replace sutures and a magnetically sensitive catheter that could treat blood clots in a minimally invasive way. They have now set their sights on using hydrogels to improve the capacity of wearable devices and medical imaging.
We are firmly in the age of wearable medical technology. Our smart watches monitor our heart rate and oxygen saturation levels and we can take EKGs with our phones. We can even measure our blood sugar with sensors inserted under the skin that send glucose data to smart devices. But these technologies have their limits. Zhao tells us that currently, “there is no wearable device that can image deep internal organs.” Nor is there a capacity in medical imaging technology for long-term imaging. The traditional ultrasound, for example, provides a snapshot of some particular tissue. But what if doctors want to monitor a patient’s heart or lungs for a longer period, during times of both rest and activity?
“These two critical needs in wearable devices and in medical imaging motivated us to invent this new bioadhesive ultrasound technology,” Zhao says. Ultrasound works by sending pulses of high-frequency sound through body tissue via a probe or transducer. The sounds echo off the tissue and return to the probe, which converts the signals it receives into images. The conventional ultrasound relies on bulky equipment and requires patients to remain still. In recent years scientists have developed smaller, stretchable devices that can be attached to the skin, but they have numerous limitations. In a paper recently published in Science, Zhao and his co-authors report that these devices suffer from “low imaging resolution, unstable imaging quality during body motions, a short continuous imaging duration (1 hour), and susceptibility to device failure.” Zhao’s lab is working to change this.
Their innovation was to attach a rigid ultrasound probe to a hydrogel-elastic polymer hybrid base. Unlike other devices, the base “effectively transmits acoustic waves, insulates the BAUS probe from skin deformation, and maintains robust and comfortable adhesion on the skin over 48 hours.” The rigid probe allows for much clearer and more consistent imaging even during stressful bodily movement. Zhao points out the immediate clinical applications this technology can have: a BAUS device “can monitor patients over the long term, providing clinicians with this kind of continuous image of diverse organs of the patients.” But Zhao also looks ahead to the potential use of BAUS tech in daily life. “Imagine you can buy a few patches, adhere them to different locations of the body, but these patches…will give you images, videos of internal organs during daily activity.” One minute you’re measuring your heart rate on your smart watch, the next you’re checking out the blood flow in your liver.
This places the power of medical imaging into the hands of ordinary people and has the potential to transform diagnostics. “Currently, if a patient feels chest pain, and then the patient goes to the hospital, they may stay in the hospital for one day, but [the chest pain] may not occur anymore,” Zhao says. “But with our technology, it’s possible in the future that once the patient feels chest pain or anything uncomfortable, they can record that image and video of the heart right at that moment, and then they can decide to send that image or video to clinicians for very early real-time diagnosis.”
For all the complexities of the science behind these innovations, Zhao and his colleagues are driven by a simple and elegant philosophy. “Let’s make people’s lives better. That’s really what everyone wants,” Zhao says. He tells us he is proud as an Asian scientist to be working on the solutions to tough problems. “Asian Americans here are making contributions to this country. I’m trying to address the grand challenges in health and sustainability facing the whole society.” The BAUS device is only one example of the ways in which Zhao’s lab is moving us toward the healthier and better world he imagines.
To stay up to date on Zhao Lab, check out http://zhao.mit.edu/.
