Research ArticleCardiac Electrophysiology

A Conformal, Bio-Interfaced Class of Silicon Electronics for Mapping Cardiac Electrophysiology

Science Translational Medicine  24 Mar 2010:
Vol. 2, Issue 24, pp. 24ra22
DOI: 10.1126/scitranslmed.3000738

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My Beating Heart

The heart is tricky to work with. Usually in constant motion, it has to be stopped for most cardiac surgery and its health is most often checked by EKG measurements of net electrical activity from outside the body. When damage to the heart causes life-threatening arrhythmias, physicians can only get a get a rough idea about where the problem is located by painstakingly recording from one part of the heart after another. Improvements in electronic circuit design and fabrication, as reported here by Viventi et al., can enable sophisticated, multiunit electrodes to stay in close contact with biological tissue, making monitoring and stimulation of the living, moving heart a realistic goal.

The new type of device is a multilayer circuit fabricated on a 25-μm-thick, plastic sheet of polyimide, with a built-in array of 288 gold electrodes. It is flexible but the design keeps the sensitive electronics in the neutral plane so that it still functions, even when bent. Each electrode has its own amplifier, which magnifies the tiny biological currents, and multiplexer, which allows the output of all 288 electrodes to be conveyed by only 36 wires. Electrically active devices inside the wet interior of the body can easily leak current, so the authors guarded against this by encapsulating the device in a trilayer coating of polyimide, silicon nitride, and epoxy. Most (75%) of the devices they made leaked less than 10 μA, an industry standard, and maintained this performance for at least 3 hours. To map cardiac function with their flexible electrode array, the researchers applied it to the exposed epicardial surface of the beating porcine heart. Functional for more than 10,000 bending cycles, the electrodes could record normal heart beats or beats driven by a second pacing electrode at high resolution. With a high signal-to-noise ratio of about 34 dB, conduction of a moving wave of cardiac activation was readily apparent as it swept across the array of electrodes with each contraction. The authors constructed an isochronal map of heart activation, determining that the conduction velocity was 0.9 mm per millisecond.

Heart physiology is not the only possible application for these flexible electrodes. The brain is also a curved, wet organ that can only be accessed by individually wired electrodes at present. Muscles are electrically active moving tissues, found both within internal organs and as effectors for the limbs. The ability to house electrodes, amplifiers, and multiplexers in a flexible, biocompatible plastic sheet that can snuggle up right against the organ of interest will improve our ability to stimulate and monitor living tissues.


  • * These authors contributed equally to this work.

  • Citation: J. Viventi, D.-H. Kim, J. D. Moss, Y.-S. Kim, J. A. Blanco, N. Annetta, A. Hicks, J. Xiao, Y. Huang, D. J. Callans, J. A. Rogers, B. Litt, A conformal, bio-interfaced class of silicon electronics for mapping cardiac electrophysiology. Sci. Transl. Med. 2, 24ra22 (2010).