A challenging implant location is in the cerebral arteries. Aneurysms exist in these contoured and narrow arteries in 6% of the population, making the development of effective treatments and follow-up monitoring critical. In the vascular system, implantable sensors must be stretchable and flexible while maintaining a low profile in order to not disrupt blood flow.
In a study recently published in Advanced Science, Robert Herbert, Woon-Hong Yeo, and co-workers from the Georgia Institute of Technology and Hanyang University introduce a fully passive, wireless, low-profile capacitive sensor and coil inductor with enhanced readout distance fabricated via aerosol jet printing (AJP).
Ag deposition with an ultrasonic atomizer (left) and enlarged view of patterned Ag on PI (right).
To fabricate the sensor, AJP was used to print four aligned layers followed by seamless integration onto a soft elastomer. In short, the sacrificial polymethyl methacrylate (PMMA) layer was spin-coated on a glass substrate, followed by a polyimide (PI) layer (dielectric layer) for transfer, which was then cured.
A silver nanoparticle (AgNP) ink (capacitive electrode) was then printed and sintered on a plasma-treated PI layer, followed by printing of a second PI and Ag layer. The PMMA was then dissolved in an acetone bath for transfer to the elastomer.
This integration process enables the sensor to conform to stents with high flexibility and stretchability and can be deployed via conventional catheter procedures.
A new inductive coupling method was also optimized and used to monitor hemodynamics via a wireless detection method at distances that surpass existing devices (6 cm). As a proof of concept, the method was tested through air, saline, beef, and in two biomimetic cerebral aneurysm models.
Mechanics of the printed biosensor for catheter-based deployment in a target vessel.