UC Berkeley

Implantable medical devices have tremendous therapeutic potential for both treatment of

disease states as well as monitoring for preventative care. To be effective, implants must

perturb host tissue as minimally as possible, while simultaneously being able to withstand

the tissue environment for a significant portion of a patient’s life. Advances in wireless

power transfer technology have made it possible to implant millimeter to sub-millimeter

scale devices fully within the body, but these devices have not been demonstrated to work

for decadal time spans.

Typical packaging material for medical implants are polymers such as silicone or parylene,

or titanium. However, polymers are not chronically hermetic due to their high water va-

por permeability and titanium is not easily amenable to electromagnetics-based wireless

communication. Ceramic materials, however, have a low water vapor permeability and are

transparent to radio-frequency radiation. Furthermore, they have had a long history in medi-

cal implants and semiconductor processing methods have greatly increased the compatibility

of ceramics processing with other materials.

This thesis explores the use of ceramics as packaging materials for wireless, miniaturized,

implantable medical devices. An alumina-titanium hybrid package is first demonstrated for

a millimeter-scale ultrasonically-coupled wireless implant. Sound propagation through solids

in two different modes is investigated, test packages are assembled, and performance is eval-

uated. Next, silicon carbide is explored as a potential packaging material for wireless radio-

frequency identification tags. A system for rapidly testing and aging silicon carbide thin-films

is designed and demonstrated, and progress towards building chronic silicon-carbide encap-

sulated radio-frequency identification tags is shown.