BIO-INTERFACED SILICON ELECTRONICS FOR NEURAL AND CARDIAC APPLICATIONS
Recent advances in material sciences have led to the development of novel silicon integrated circuits that can be deployed on ultrathin plastic and elastomeric surfaces. This technology allows for sheets of active, amplified and multiplexed electrodes that are flexible, stretchable and compatible with biological applications. This thesis reports the development of a conformal, bio-interfaced class of silicon electronics for measuring signals from the dynamic, three-dimensional surfaces of soft tissues in the human body. The critical components of this research are: (1) Adapting materials science advances to biological applications by making them biocompatible, operable while submersed in conductive fluid and flexible enough to allow recording from irregularly-shaped, moving surfaces; (2) Designing circuits for sampling low-noise biological signals with a high degree of multiplexing by using active electronics positioned at each individual sensor; and (3) Demonstrating practical functionality in real clinical situations, such as recording from beating hearts and previously inaccessible regions of brain, in vivo.
The first section of this work describes proof of principle experiments that demonstrate basic biological interaction capability for passive electrode array devices manufactured using new transfer printing techniques. The second section describes a new type of electrode array that relies on ultrathin electronics supported by bioresorbable substrates of silk fibroin. Specialized mesh designs and ultrathin forms for the electronics ensure minimal stresses on the tissue and highly conformal coverage, even for complex curvilinear surfaces. The third section demonstrates a sensor system composed of 2016 silicon nanomembrane transistors configured to record electrical activity directly from the curved, wet surface of a beating heart, in vivo. The fourth and final section shows the development of new dense arrays of multiplexed electrodes using flexible electronics that can enable an unprecedented level of spatial and temporal electrocorticographic (ECoG) resolution over large areas of cortex. The extreme flexibility of the devices can further enable simultaneous sampling of gyral and intrasulcal ECoG to sample regions of the brain that were previously inaccessible or difficult to reach, but are known to carry enormously important information.
These successful, clinical demonstrations represent two examples of many possible uses of this electronics technology in advanced, minimally invasive medical devices that will provide direct benefits to human health from their advanced capabilities.