Text

theses

Functional loss and impairment of skeletal muscle could occur as a result of a diverse range of causes including trauma, aging, and diseases such as amyotrophic lateral sclerosis, negatively impacting the lives of more than 2 million people in the United States. Existing solutions for the repair and regeneration of skeletal muscle display contractility only “after” new muscle has been regenerated, which is typically a lengthy process. Such limitations highlight the need for the development of new technologies that can provide function and regeneration of lost tissue in a timely manner. A possible solution to enable patients with immediate function as new tissue regenerates is the development of new classes of subcutaneous muscle prosthesis, which are envisioned to be made by combining biomaterials such as ionic electroactive polymers (iEAPs) with their implantable controllable electrical stimulators. Towards this goal, the work presented here proposes novel circuit-level and system-level solutions for the design and realization of wirelessly tunable electrical stimulators for iEAPs. The first part of this dissertation focuses on the problem of implementing precise reference circuits that will be required in stimulators. Three novel design solutions are presented. First, a BiCMOS-based curvature compensation technique, which can be realized in any BiCMOS/CMOS technology, is proposed to completely cancel the nonlinear temperature dependent terms of the base-emitter junction voltage in bandgap reference voltage circuits. Second, a new design solution based on the bandgap voltage difference of Si and SiGe p-n junctions is proposed to significantly improve the accuracy of SiGe-based reference circuits. For both proposed solutions, theoretical derivations are presented, and circuits are designed, fabricated, and experimentally characterized. Finally, a multi-piecewise solution is presented which results in references with maximum stability. The second part of the dissertation focuses on the design of the tunable stimulators and their integration with iEAPs. The unique characteristics of iEAPs impose several design challenges for the stimulator. These challenges are identified, and solutions are proposed. The electrical stimulation is proposed to be provided using a tunable external capacitor-less low dropout regulator (LDO). To enable remote tuning, the frequency at the primary side is utilized to wirelessly adjust the magnitude of the voltage from the LDO, and hence, the electric field generated at the secondary side (implant). Furthermore, a system-level solution is presented to remotely control the polarity of the electric field as well as its magnitude, enabling iEAPs with a wide range of movement possibilities. The performance of the proposed stimulator in generating reliable output is extensively evaluated experimentally under various conditions, including coil misalignment. The stimulator is integrated with iEAP samples, and the functionality of the endto-end module is examined based on the response and the movement characteristics of iEAPs in a series of in vitro experiments. Results demonstrate the feasibility of using the proposed system as a reliable tunable electrical stimulator for iEAPs.

ETD_8306

Ph.D.

Includes bibliographical references

by Yi Huang

doi:10.7282/T36113FR

ETD doctoral

The author owns the copyright to this work.