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Flexible Microimplants for In Vivo Sensing


Zhao, Yu (2014) Flexible Microimplants for In Vivo Sensing. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/SHYA-5Y51.


The work in this thesis develops two types of microimplants for the application of cardiovascular in vivo biomedical sensing, one for short-term diagnosis and the other for long-term monitoring.

Despite advances in diagnosis and therapy, atherosclerotic cardiovascular disease remains the leading cause of morbidity and mortality in the Western world. Predicting metabolically active atherosclerotic plaques has remained an unmet clinical need. A stretchable impedance sensor manifested as a pair of quasi-concentric microelectrodes was developed to detect unstable intravascular. By integrating the impedance sensor with a cardiac catheter, high-resolution Electrochemical Impedance Spectroscopy (EIS) measurements can be conducted during cardiac catheterization. An inflatable silicone balloon is added to the sensor to secure a well-controlled contact with the plaque under test in vivo. By deploying the device to the explants of NZW rabbit aorta and live animals, distinct EIS measurements were observed for unstable atherosclerotic plaques that harbored active lipids and inflammatory cells.

On the other hand, zebrafish (Danio rerio) is an emerging genetic model for heart regenerative medicine. In humans, myocardial infarction results in the irreversible loss of cardiomyocytes. Zebrafish hearts can fully regenerate after two months with 20% ventricular resection. Long-term electrocardiogram (ECG) recording can characterize the heart regeneration in a functional dimension. A flexible microelectrode membrane was developed to be percutaneously implanted onto a zebrafish heart and record epicardial ECG signals from specific regions on it. Region-specific aberrant cardiac signals were obtained from injured and regenerated hearts. Following that, in order to achieve continuous and wireless recording from non-sedated and non-restricted small animal models, a wireless ECG recording system was designed for the microelectrode membrane, prototyped on a printed circuit board and demonstrated on a one-day-old neonatal mouse. Furthermore, a flexible and compact parylene C printed circuit membrane was used as the integration platform for the wireless ECG recording electronics. A substantially miniature wireless ECG recording system was achieved.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Micro implants, In vivo sensing, parylene, MEMS, biomedical
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Tai, Yu-Chong
Thesis Committee:
  • Choo, Hyuck (chair)
  • Hsiai, Tzung
  • Yang, Changhuei
  • Dabiri, John O.
  • Tai, Yu-Chong
Defense Date:3 June 2014
Non-Caltech Author Email:zhaoyuisanapple (AT)
Record Number:CaltechTHESIS:06092014-120248372
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8508
Deposited By: Yu Zhao
Deposited On:03 Oct 2014 17:23
Last Modified:04 Oct 2019 00:05

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