Accuracy and Longevity of an Implantable Continuous Glucose Sensor in the PRECISE Study: A 180-Day, Prospective, Multicenter, Pivotal Trial

It is known that continuous glucose monitoring (CGM) systems can lower mean glucose compared with episodic self-monitoring of blood glucose. Implantable CGM systems may provide additional benefits. We studied the Eversense (Senseonics Inc.) implantable CGM sensor in 71 participants aged 18 years and older with type 1 and type 2 diabetes in a 180-day multinational, multicenter pivotal trial. Participants used the CGM system at home and in the clinic. CGM accuracy was assessed during eight in-clinic visits with the mean absolute relative difference (MARD) for venous reference glucose values >4.2 mmol/L as the primary end point. Secondary end points included Clarke Error Grid Analysis and alarm performance. The primary safety outcome was device-related serious adverse events. This trial is registered with ClinicalTrials.gov, number NCT02154126. The MARD value against reference glucose values >4.2 mmol/L was 11.1% (95% CI 10.5, 11.7). Clarke Error Grid Analysis showed 99.2% of samples in the clinically acceptable error zones A and B. Eighty-one percent of hypoglycemic events were detected by the CGM system within 30 min. No device-related serious adverse events occurred during the study. Our results indicate the safety and accuracy of this new type of implantable CGM system and support it as an alternative for transcutaneous CG

Remotely-powered wireless monitoring systems.

This thesis presents work on the theory, implementation, and characterization of passive-telemetry-based wireless systems realized for both biomedical and environmental monitoring. These systems utilize a loosely-coupled transformer to enable sensing systems that provide remote readout of temperature, absolute pressure, and relative humidity. The fundamental limits in device size, wireless range, and sensor resolution have been explored for both passive and active systems. High performance passive telemetry systems have been developed to realize systems that employ the methodology developed in exploring the fundamental limitations of this technology. A fully passive device has been developed implementing resonant-frequency-shifting passive telemetry in a wireless pressure sensor. The wireless sensor has been realized as a double-sided single-chip device that utilizes a bulk-micromachined capacitive pressure transducer and an on-chip spiral antenna. The device is designed for intracranial pressure monitoring and measures 6mm x 6mm x 0.5mm with a resonant frequency of 12MHz. The pressure sensor is fabricated using a dissolved-wafer silicon-on-glass process. This system implements low-impedance, front-to-back interconnect for the glass die as well as high-Q on-chip inductors. The device has been utilized for signal readout with coupling distances approaching 4cm. Tradeoffs between resolution and coupling range limit the coupling distance to 8mm for a 1mmHg pressure resolution. This thesis work has also developed hybrid and integrated versions of passive-telemetry systems that implement backscatter modulation to transmit sensor information to the interrogator systems. The hybrid system is implemented using a single chip transducer front-end that monolithically integrates transducers for temperature, pressure, and relative humidity in a silicon-on-glass process. This process combines anodic bonding and a silicon-gold eutectic to realize vacuum-sealed cavities with low-impedance (6O) electrical feedthroughs. Temperature is sensed capacitively using a row of Si/Au bimorph beams that produce a sensitivity of 15fF/°C from 20 to 100°C. The absolute pressure sensors have a sensitivity of 15fF/Torr and a range from 500 to 1200Torr, and the relative humidity sensor responds with 39fF/%RH from 20--95%RH. A relaxation oscillator implements low-power capacitance-to-frequency conversion on a second chip with a sensitivity of 750Hz/pF at 15kHz, forming a 341muW transducer interface. (Abstract shortened by UMI.)Ph.D.Applied SciencesElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124388/2/3138138.pd

Micro Thermoelectric Cooler Fabrication: Growth and Characterization of Patterned Sb 2 Te 3 and Bi 2 Te 3 Films

Abstract A column-type micro thermoelectric cooler is being fabricated using p-type Sb 2 Te 3 and n-type Bi 2 Te 3 films (approximately 4 µm thick). The films are grown by thermal co-evaporation and patterned on Cr/Au/Ti/Pt (hot) connectors, which are deposited onto a silicon dioxide coated wafer. The column height is limited by control of the Te deposition rate. Although a high substrate temperature during thermoelectric film deposition is desired, it has been limited by the degradation of the photoresist used for patterning. The measured Seebeck coefficient and electrical resistivity of the thermoelectric films are reported, and preliminary results show that excess tellurium increases the Seebeck coefficient