Article Source: IMechE

A stretchy 3D-printed sensor implanted in patients’ brains could cheaply, safely and easily monitor life-threatening aneurysms – all without a battery or other internal power source.

Created by Woon-Hong Yeo and colleagues at Georgia Tech, the wireless device is small enough to be implanted in the brain’s blood vessels. The sensor would be wrapped around stents or diverters implanted to control blood flow in vessels affected by aneurysms – bulges that can cause death or serious injury if they burst.

The team used aerosol jet 3D printing to create conductive silver traces on elastomeric substrates, reducing potential costs and accelerating manufacturing. The technique uses a spray of aerosol particles to create patterns, allowing narrower feature sizes than conventional inkjet printing. The process allows production in a single step, without traditional multi-step lithography processes in a cleanroom. This reportedly enables higher volume manufacturing at lower cost.

The researchers said the device is believed to be the first demonstration of aerosol jet 3D printing to produce an implantable, stretchable sensing system for wireless monitoring.

“The beauty of our sensor is that it can be seamlessly integrated onto existing medical stents or flow diverters that clinicians are already using to treat aneurysms,” said Yeo. “We could use it to measure an incoming blood flow to the aneurysm sac to determine how well the aneurysm is healing, and to alert doctors if blood flow changes.”

Inserted using a catheter system, the sensor would use inductive coupling of signals to allow wireless detection of ‘biomimetic cerebral aneurysm haemodynamics’. The device could detect blood flow changes as small as 0.05m/s.

Monitoring the progress of cerebral aneurysms currently requires repeated angiogram imaging using contrast materials that can have harmful side effects. Because of the cost and potential negative effects, use of the technique must be limited – but a sensor placed in a blood vessel could allow more frequent evaluations without the use of imaging dyes.

The six-layer sensor is made of biocompatible polyimide, two separate layers of a mesh pattern produced from silver nanoparticles and a dielectric and soft polymer-encapsulating material. The sensor would be wrapped around stent or flow diverters less than 3mm in diameter.

The device includes a coil to pick up electromagnetic energy transmitted from another coil outside the body. Blood flowing through the implanted sensor changes its capacitance, which alters the signals passing through the sensor on the way to a third coil located outside the body. In the laboratory, Yeo and colleagues measured capacitance changes 6cm away from a sensor implanted in meat to simulate brain tissue.

The researchers now plan to include blood pressure sensing alongside flow rates. Yeo’s research team has also developed a flexible and wearable health monitor able to provide ECG and other information.

The work was published in Advanced Science.

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