Clinicians believe that a wireless sensor small enough to be implanted in the blood vessels of the human brain could help clinicians evaluate the healing of aneurysms, a common cause of serious injury and often death.
Aneurysms are outward bulging in blood vessels, caused by a weak spot in a vessel's wall, that are prone to bursting. The wireless, stretchable sensor could potentially help clinicians wirelessly monitor their healing. The sensor is inserted into a blood vessel using a catheter-like system and can be wrapped around implanted stents that control vascular blood flow that has been affected by an aneurysm.
Wood-Hong Yeo, Assistant Professor at Georgia Tech's School of Mechanical Engineering, said, “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…We could use it to measure incoming blood flow to the aneurysm sac to determine how well the aneurysm is healing, and alert doctors if blood flow changes.”
Georgia Tech's report, published in the Advanced Science journal on August 7, detailed how the stretchable wireless sensor works.
How the Sensor Works
The sensor uses an inductive signal coupling to wirelessly detect biomimetic cerebral aneurysm hemodynamics. The sensor, wrapped around the stent or flow diverter, includes a coil that picks up electromagnetic energy that is transmitted from a different coil located outside of the patient's body. It must be less than two-to-three millimeters in diameter in order to fit into blood vessels.
As blood blows through the vessel, the sensor's capacitance changes and this alters signals that are passing through the sensor towards the external coil.
The stretchable blood flow sensor. Image courtesy of Georgia Tech.
Georgia Tech's sensor is capable of measuring blood flow changes as small as 0.05 meters per second. This means that for patients who have undergone medical procedures, clinicians would be able to deduce whether their aneurysm is occluding as expected without the use of imaging tools.
Up until now, the monitoring of cerebral aneurysms has required the use of angiogram imaging that uses contrast materials with potentially harmful side effects. Due to the potential for side effects and the sheer cost of imaging, use is limited.
The team behind the sensor at Georgia Tech hopes that the next phase of the project will allow the sensor to measure blood pressure and blood flow rates. By being able to measure pressure, Professor Wood-Hong Yeo said that it "…would allow the device to be used for other applications, such as intracranial pressure measurements.”
How the Sensor was Made
Made possible using aerosol jet 3D printing, the stretchable wireless sensor is made up of six layers and is fabricated from biocompatible polyimide, two separate layers of a mesh pattern made from silver nanoparticles, a dielectric, and a soft polymer-encapsulating material.
According to the Georgia Tech team, using 3D additive manufacturing allows them to include very small electronic features and produce them in a single step. This eliminates the need for multistep lithography, allowing for higher-volume, lower-cost production.
Georgia Tech's research was supported by the Korean Institute of Industrial Technology and a seed grant from Georgia Tech's Institute for Electronics and Nanotechnology.