Title:
Materials and microfabrication approaches for completely biodegradable wireless micromachined sensors

dc.contributor.advisor Allen, Mark G.
dc.contributor.author Luo, Mengdi
dc.contributor.committeeMember Brand, Oliver
dc.contributor.committeeMember Lin, Zhiqun
dc.contributor.committeeMember Singh, Preet
dc.contributor.committeeMember Yao, Donggang
dc.contributor.department Materials Science and Engineering
dc.date.accessioned 2015-01-12T20:53:11Z
dc.date.available 2015-01-12T20:53:11Z
dc.date.created 2014-12
dc.date.issued 2014-11-17
dc.date.submitted December 2014
dc.date.updated 2015-01-12T20:53:11Z
dc.description.abstract Implantable sensors have been extensively investigated to facilitate diagnosis or to provide a means to generated closed loop control of therapy by yielding in vivo measurements of physical and chemical signals. Biodegradable sensors which degrade gradually after they are no longer functionally needed exhibit great potential in acute or shorter-term medical diagnostic and sensing applications due to the advantages of (a) exclusion of the need to a secondary surgery for sensor removal, and (b) reduction of the risk of long-term infection. The objective of this research is to design and characterize microfabricated RF wireless pressure sensors that are made of completely biodegradable materials and degrade at time-controlled manner (in the order of years and months). This was achieved by means of investigation of appropriate biodegradable materials and development of appropriate fabrication processes for these non-standard (Microelectromechanical systems) MEMS materials. Four subareas of research are performed: (1) Design of sensors that operate wirelessly and are made of biodegradable materials. The structure of the wireless sensor consists a very compact and relatively simple design of passive LC resonant circuits embedded in a polymer dielectric package. To design the sensor with a particular resonant frequency range, an electromagnetic model of the sensor and a mechanical model for circular plate are developed. The geometry of the sensor is established based on the analytical and finite element simulations results. (2) Investigation of the biodegradable materials in the application of implantable biodegradable wireless sensors to achieve controllable degradation lifetimes. Commercially available and FDA approved biodegradable polymers poly(L-lactic acid) (PLLA) and a "shell-core" structure of poly(lactic-co-glycolic acid) (PLGA) and polyvinyl alcohol (PVA) are utilized as the dielectric package for slow and rapid degradation sensors, respectively. Biodegradable metallic zinc and zinc/iron couples are chosen as conductor materials. The degradation behavior of Zn and Zn/Fe-couple are investigated in vitro. (3) Development of novel fabrication processes. The process exploit the advantages of MEMS technology in fabricating miniaturized devices, while protecting vulnerable biodegradable materials from the strong and/or hazardous chemicals that are commonly used in conventional MEMS fabrication process. These new processes enable the fabrication of biocompatible and biodegradable 3-D devices with embedded, near-hermetic cavities. (4) Testing the pressure response functionality and studying the degradation behavior of the wireless biodegradable pressure sensors. Both PLLA-based and PLGA/PVA-based sensors are characterized in vitro by being immersed in 0.9% saline for prolonged time. All the sensors exhibit three stages of behavior in vitro: equilibration, functional lifetime, and performance degradation. During the functional lifetime, most sensors exhibit fully stable functionality. The PLLA-based sensors show no significant weight loss within 8 month and are expected to fully degrade after 2 years, while the PLGA/PVA-based sensors can degrade completely within 26 days.
dc.description.degree Ph.D.
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/53093
dc.language.iso en_US
dc.publisher Georgia Institute of Technology
dc.subject MEMS
dc.subject Biodegradable sensors
dc.subject Wireless passive sensors
dc.subject RF pressure sensors
dc.subject Galvanic corrosion
dc.subject Poly(lactic acid)
dc.subject Poly(lactic-co-glycolic acid)
dc.subject In vitro degradation
dc.title Materials and microfabrication approaches for completely biodegradable wireless micromachined sensors
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.corporatename School of Materials Science and Engineering
local.contributor.corporatename College of Engineering
relation.isOrgUnitOfPublication 21b5a45b-0b8a-4b69-a36b-6556f8426a35
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
thesis.degree.level Doctoral
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