Wireless electrical stimulators for nanofibers with application in next generation muscle prosthesis
Creators: name: Huang, Yi
Publisher: name: No Publisher Supplied
Year: 2017

description: 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.