ESE Ph.D. Thesis Defense: “The Development of A Fingertip Implantable MEMS Tactile Sensing System”

Abstract: This thesis explores the development of a fingertip implantable MEMS tactile sensing system to provide tactile sensing capabilities for paralyzed people using a brain machine interface (BMI) technology. With the BMI-controlled stimulation, paralyzed people are able to restore hand movement with their native hands without sensation. However, sensory feedback for these BMI-controlled stimulators is still missing. To overcome the barrier, development of a tactile sensing system is necessary. In previous studies, multiple approaches have been exploited to realize fingertip tactile recognition for wearable electronics, prosthetics, and robotics. Compared with these existing tactile sensors with wearable devices or robotic arms, we are interested in combining tactile sensing with implantable MEMS technologies. In this dissertation, we build an implantable tactile sensing system with wireless power and signal transmission capabilities for somatosensory feedback of BMI systems.

Toward these goals, a fused silica package with good hermeticity to moisture, biocompatibility, CMOS compatibility, as well as multiple feed-throughs for electronic access was developed and characterized. A localized fusion bonding technology by using CO2 laser-assisted machining was proposed to achieve simultaneous bonding and dicing of fused silica wafer stacks.

To demonstrate an implantable tactile sensor, a capacitive force-sensing technology based on the packaging technology was developed to satisfy hermetic and biocompatible requirements for implantation applications. The performance of this tactile sensor is investigated with quantitative static and dynamic loading measurements. In addition, both in vitro study with the sensor embedded under skin-phantom and implantation in a monkey hand are examined.

To further develop an implantable tactile sensing system with wireless communication capability, a multilayer fused silica structure incorporating a capacitive force sensor, an ASIC for wireless power and data communication, and the hermetic package technology for encapsulating the electronics is built. The development of an antenna coil integrated with the system was presented and the fabrication process of the system is discussed. To characterize the tactile sensing system, a customized experimental setup is employed and static loading measurement with dynamic loading analyzer is performed verifying that both of the pressure sensing and wireless transmission of the system are functional. This wafer-level technology will be very useful for other implantable pressure sensing and MOEMS applications.

Advisor: Mark G. Allen, Alfred Fitler Moore Professor of Electrical and Systems Engineering, University of Pennsylvania

Dissertation Committee:

Chair: Jan Van der Spiegel, Professor of Electrical and Systems Engineering, University of Pennsylvania

Member: Firooz Aflatouni, Associate Professor of Electrical and Systems Engineering, University of Pennsylvania

Member: Igor Bargatin, Associate Professor of Mechanical Engineering and Applied Mechanics, University of Pennsylvania

Member: Troy Olsson, Assistant Professor of Electrical and Systems Engineering, University of Pennsylvania