Medication compliance is the degree to which a medication is taken according to a prescribed treatment and is usually measured in terms of percent of doses taken over a given interval. It is estimated 125,000 people die of treatable ailments because of poor adherence. A tenth of hospital admissions are associated with noncompliance at a healthcare services expense of approximately $15.2 billion annually. Motivated in part by the need for new alternatives for measuring medication compliance, the primary objective of this dissertation is to investigate the feasibility of small electronic transponders as potential means for low cost and reliable detection schemes of orally ingestible electronic pills (e-pills). With continued advances in RF biotelemetry, it is envisioned that an external monitoring point-of-care device or a body-worn electronic sensor can be used to detect the presence of the pill in the stomach or GI-tract after ingestion.

The proposed medication compliance device comprises of an electronic microchip and an antenna inlay placed on the surface of a standard 0 or 00 sized capsule. These antennas can be made of conductive bio-compatible coatings by incorporating a metal, which can dissolve, such as silver, under a temporary protective layer such as polyglycolic acid, or by incorporating particles that are non-toxic by virtue of being non-absorbable. Thus, the substrate for the antenna and the electronic device can be directly applied onto the surface of the drug delivery device without affecting the volume reserved for the medication. The electronic pill in this system-on-acapsule can be potentially manufactured in large scales using a thin, mechanically compliant and small antenna pill inlay under a biocompatible protective coating that is excreted via the GI tract.

This work begins with an overview of medication compliance and current techniques of measuring medication adherence. A brief review of potential alternatives based on electrical identification technologies is presented. We devote a large portion of this thesis to understanding the transmission characteristics of small electronic radiating elements inside the human body. Initial feasibility studies are carried out using small coil antennas inside human phantom solutions that mimic the electrical properties of the human body. Studies are supported by extensive simulations of radiating elements inside the human body using the finite difference time domain (FDTD) technique. The radiated field intensity over several US Federal Communications Commission (FCC) telemetry bands was characterized to determine optimal UHF transmission frequencies and suitable locations for external reader placement. This dissertation also investigates a variety of capsule antenna designs, direct on-capsule printing methods and measurement infrastructure to experimentally characterize the antenna pills.

This work introduces a novel radio frequency identification transponder design, called “e-Burst”, which enables detection of passive electronic pills inside the human body. The critical insight of the proposed RF tagging architecture is the use of an effective signal coupling methodology and an asymmetric powering and communication scheme to circumvent problems associated with signal attenuation inside the human body and poor radiation efficiency of electrically small antennas. Since the power levels required to activate a tag are orders of magnitude larger than what is detectable externally, the tag employs a galvanic coupling method to energize the microchip at low frequencies where in-body attenuation is lowest, and generates RF bursts at higher frequencies where the efficiency and fractional bandwidth of a capsule-sized antenna is higher. The operation of the tagging system can be treated as a two-step energy conversion process where low frequency energy transferred from the reader device is first converted into DC to energize the tagging device, and the stored DC energy on the tagging device is then converted to the UHF RF bursts to show the presence of the tagging device. Critical design parameters for overall system level analysis incorporating experimentally characterized channels using human cadaver are presented. Based on these studies, a proof-of-concept asymmetric RF tagging device was fabricated using 130nm CMOS technology and validated inside phantom solutions.