Silicon based co-integrated bioelectrical and biomechanical interfaces: Applications to insect olfactory neural interfaces, miniature neural interfaces, and cardiac excitation characterization

Biosensors have been extremely important in revolutionizing healthcare and environmental monitoring. In combination with Microelectromechanical Systems (MEMS) devices, biological systems can be probed on similar micro and nano dimensions. This can provide a better understanding of how biological systems function and allow for improved treatment methods for diseases and other maladies. However, there are still key limitations in advancing biosensor technology. One of the limitations is biological integration of sensors with tissue for robust interfaces that minimally damage the tissue and can be used in long-term implantations.;In this dissertation, three projects are presented where strategies have been used and developed to minimize biosensor invasiveness. Ultrasonic horn probes driven at their longitudinal resonances can allow penetration of tough tissue, such as cardiac tissue or the dura layer surrounding the brain. For cardiac tissue, ultrasonic probes can allow study of the onset of arrhythmias in 3D. A model governing the force reduction propertions of ultrasonic horn probes dependent on driving voltage, insertion velocity, and substrate elasticity is presented to guide design and use of ultrasonic horn probes in a variety of tissues. The first three-dimensional recordings of action potential propagation during ischemia are obtained. The results show the change in activation delay, action potential duration, action potential amplitude, and morphology through the tissue thickness with ischemia.;Secondly, based on the ultrasonic horn design, a new miniature neural interface system is introduced. This system can allow study of probe insertion force effects on long-term reactions, stress fields around the inserted probes, and changes in electrode impedance and electrical activity from nearby cells over time.;Thirdly, a new hybrid insect olfactory sensor system for gas sensing is presented, which uses Early Metamorphosis Insertion Technology (EMIT) to achieve probe integration. The presented olfactory sensor is based on a silicon neural electrode and is shown to monitor responses to pheromone components and the host plant of the insect, Manduca sexta. The probe sensor is lightweight enough to be carried on the moths.;In the context of these projects, wireless system designs and implementations are presented that allow portability and parallel recording from the tissue. The first system presented is used for wireless transmission of cardiac action potentials, and the second is designed for multiplexed wireless transmission of neural signals. By making the probe and data collection systems fully wireless, wire-induced stresses on probes integrated with tissue can be reduced and serve to reduce damage to the tissues.