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Flexible Sensors Offer View into Epileptic Seizures

Brain activity can be monitored and sampled using minimal amount of wires and electrodes and improving implantable devices.

Tapping into the human brain to understand its functions in daily life — as well as its malfunctions in illness — has long been a challenge for researchers. Mapping brain activity requires unwieldy, invasive arrays of electrodes and sensors that can damage tissue while only reading activity in a limited area. A team of researchers at the Polytechnic Institute of New York University (NYUPoly) partnering with researchers from the University of Pennsylvania and the University of Illinois at Urbana-Champaign, have devised a streamlined, minimally invasive brain interface that may yield new insights into the causes of brain diseases like epilepsy and could potentially lead to new implantable neuroprosthetic and diagnostic devices.

altAt the core of the research is a novel, implantable electrode array integrating ultra-thin, flexible silicon transistors capable of sampling large areas of the brain with minimal wiring. The technology has been licensed to mc10, a Boston-area company delivering flexible electronics for industrial and biomedical applications.

Current efforts to record or stimulate brain activity are limited by the need to wire each individual sensor at the electrode-tissue interface. The resulting mass of leads is cumbersome and renders a high-resolution map of large areas logistically impossible.

This new approach enables dense arrays of thousands of multiplexed sensors that provide unprecedented spatial resolution — more than 400 times the current level — with a fraction of the wires. In experiments, just 39 wires were required for 360 electrodes. The design can be readily scaled to thousands of electrodes, while maintaining a small number of wires. The arrays are also non-penetrating and, unlike current techniques, cause little or no damage to fragile brain tissue. The use of flexible silicon also allows active circuitry to be built right at the brain surface.

Conventional circuits are built on rigid silicon, which doesn’t conform to the body. Ultra-thin silicon retains its performance but is also flexible, making it suitable for implantable devices. (See Figure 1).

In experiments, the research team deployed the system to record various types of brain activity in animals, including sleep and visual responses and observation of the brain during an epileptic seizure. Their techniques may improve understanding of what causes epilepsy and lead to implantable technologies to stop or prevent seizures in patients.

The researchers believe this is the first reported use of ultrathin, flexible silicon in a brain interface device. The research also holds promise for other medical applications, including dramatic improvements of existing implantable devices such as cardiac pacemakers and defibrillators, cochlear and retinal implants and motor prosthetic systems.

The longer-term goal is to configure these implantable arrays for use anywhere in the body, equipped with wirelessly controlled sensors capable of multiple functions such as recording, stimulating and ablating.

The research was conducted with support from the U.S. National Institutes of Health’s National Institute of Neurological Disorders and Stroke and its National Heart, Lung, and Blood Institute; the National Science Foundation; the U.S. Department of Energy Division of Materials Sciences; Citizens United for Research in Epilepsy; and the Mirowski Discovery Fund for Epilepsy Research.

This technology was conducted by a team of researchers from the Polytechnic Institute of New York University, New York, NY, the University of Pennsylvania, Philadelphia, PA, and the University of Illinois at Urbana-Champaign. For more information, visit http://www.poly.edu.