A wireless sensor that can be implanted in the blood vessels of the human brain has recently been developed by a team of researchers. Researchers from Georgia Tech and Emory University suggest that the technology could potentially help clinicians to wirelessly monitor and evaluate the healing of aneurysms. The sensor is inserted using a catheter system, and it can be wrapped around implanted stents or diverters that control blood flow in the vessels affected by aneurysms.
“The beauty of our sensor is that it can be seamlessly integrated into existing medical stents or flow diverters that clinicians are already using to treat aneurysms,” said Woon-Hong Yeo, an assistant professor at Georgia Tech’s George W. Woodruff School of Mechanical Engineering and the Wallace H. Coulter Department of Biomedical Engineering. “We could use it to measure an incoming blood flow to the aneurysm sac to determine how well the aneurysm is healing, and alert doctors if blood flow changes.”
The sensor uses inductive coupling of signals to wirelessly detect biomimetic cerebral aneurysm hemodynamics. It includes a coil to detect electromagnetic energy transmitted from another coil located outside the body. The sensor will be wrapped around the stent or flow diverter, which must be less than two or three millimeters in diameter to fit into the blood vessels.
The blood flowing through the sensor changes its capacitance. This alters the signals passing through the sensor toward a third coil located outside the body. In the next phase of the project, the aneurysm sensor will also be able to measure blood pressure in the vessel along with the flow rates.
“We will be able to masure how pressure contributes to flow change,” Yeo explained. “That would allow the device to be used for other applications, such as intracranial pressure measurements.”
Besides allowing for wireless monitoring, the sensor can also operate without the use of batteries.
The sensor is comprised of six layers. It is fabricated from biocompatible polyimide, two separate layers of a mesh pattern produced from silver nanoparticles, a dielectric, and soft polymer-encapsulating material. This is made possible through the use of aerosol jet 3D printing.
According to the engineers, the use of 3D additive manufacturing allows very small electronic features to be produced in a single step. This eliminates the need for the traditional multistep lithography process altogether. Subsequently, this means that the sensor can be manufactured at a higher volume and a low cost.
The technology is capable of producing conductive silver traces on elastomeric substrates and is said to be the first demonstration of an aerosol jet 3D printer producing an implantable, stretchable sensing system for wireless monitoring.
Monitoring the progress of cerebral aneurysms today requires repeated angiogram imaging through contrast materials. Not only is this costly, but it can also create harmful side effects. According to the research team, these drawbacks should limit the use of the imaging technique. Alternatively, a sensor inside the blood vessel could allow for more frequent evaluations without the use of imaging dyes.
“For patients who have had a procedure done, we would be able to tell if the aneurysm is occluding as it should without using any imaging tools,” said Yeo. “We will be able to accurately measure blood flow to detect changes as small as 0.05 meters per second.”
Additionally, the research team has developed a wearable health monitor that can provide ECG and other information. According to Yeo, the success of their technology signals the potential of smart and connected wireless soft electronics—nanomaterials, stretchable materials, and machine learning algorithms—in healthcare.
“We are excited that people are now recognizing the potential of this technology,” Yeo said. “There are a lot of opportunities to integrate this sensing mechanism into ultrathin membranes that are implantable within the body.”
The research was supported by the Korean Institute of Industrial Technology. A seed grant was awarded by the Georgia Tech Institute for Electronics and Nanotechnology. The report was published on August 7 in the Advanced Science journal.
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