Publication Date

2011

Document Type

Thesis

Committee Members

Kuan-lun Chu (Committee Member), Andrew Hsu (Other), Saiyu Ren (Committee Member), Kefu Xue (Committee Member), Yan Zhuang (Committee Chair)

Degree Name

Master of Science in Engineering (MSEgr)

Abstract

Biosensors are becoming more popular recently and expanding due to their broad applications in detecting disease and infectious agents, monitoring of environmental toxins, etc. Recognition and quantification of biochemical molecules and molecular interactions present great challenges in biosensing [38]. Impedance sensing at radio frequency (RF) /microwave frequency becomes very attractive as bio-molecules exhibits large distinct dielectric properties, and also because the ionic conductivity of water in most physiological systems is greatly diminished. For example, it has been reported that tumoral cells exhibits large value of electrical conductivity and permittivity which can result in significant variation of the impedance when compared to the normal cells [38]. The dynamic processes occurring in several microscopic, mesoscopic, and macroscopic organisms play key roles in device sensing and can be effectively monitored by impedance characterization. Graphene and its derivatives have attracted much attention recently for their application in biological sensing systems because of their unique 2D structure, flat planar surface and electronic properties. In this thesis, we made use of on-chip integrated impedance bio-sensors using coplanar waveguides (CPWs) as the sensing platform. Absorption of chemicals like Chitosan and DNA on graphene (or) graphene derivatives lead to remarkable red-shift of the resonant frequencies [38]. Substrate complex permittivity has been extracted from the simulation by using the ADS (Advanced design system) software. The imaginary part of the permittivity indicated significant leakage currents in the graphene/graphene derivatives, Chitosan, and DNA [38]. In this thesis, a proof-concept of transmission line based RF/microwave frequency has been reported for impedance bio-/chemical-sensor. The results showed that adding biomolecules to graphene oxide coated CPW sensors caused significant red-shift in the resonance frequency and the decrease of the resistance of the resonant frequencies, reflecting the change of the complex permittivity of the attached biomolecules. The experimental results obtained have also been verified by performing the 2D simulation [38]. On the other hand low loss conductors can be used and easily integrated with the high speed electronic circuits. They are basically used to overcome the drawback caused due to interconnect RC delay and also to improve the passive components present on the circuit. Earlier devices occupied more area and increased the cost of the system. Low ferromagnetic frequency (FMR), eddy current loss, magnetic loss etc, caused the poor quality factor inspite of adding thin ferromagnetic films like "Ni80Fe20" [35].The interconnect RC delay causes drawbacks such as low speed, energy dissipation, signal integrity etc which become more severe as we move to higher generation of technology (35 nm). Low loss artificial conductor based on ARLYM superlattice is being used to improve the passive components present on the circuit and also to overcome the issue with RC delay [35]. Thus, this approach of using the low loss artificial conductor method is been used for demonstrating the on-chip inductors having high quality factor and can be easily used for high speed electronics. Thus, this approach is proved to be very effective based on artificial layered material consisting of layers of "Ni80Fe20" (or) "Cu" superlattice [35]. By adjusting the thickness between the two layers the skin effect can be reduced to a great extent by using the high saturation material named "FeCo" to a minimum frequency [35].

Page Count

86

Department or Program

Department of Electrical Engineering

Year Degree Awarded

2011

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