A platform of CMOS-MEMS microcantilever for biochemical detection and characterization of thin-film transistor-embedded signal transduction
Date Issued
2012
Date
2012
Author(s)
Kuan, Shu
Abstract
The bendable microcantilever (MCL) which was the central element in many mechanical stress sensors have proven to be a valuable tool in the advancing fields of biologically inspired sensing or actuating system. This study focuses on the development of CMOS compatible microcantilever for novel biomolecular detection and the characterization of Thin-film Transistor (TFT)-embedded signal transduction. The evolution towards transistor- based readout technique can provide the growing need for a compact device with multiplexed sensing of multiple biomarkers in the future.
In biomolecular application, this work reports the label-free binding kinetics of fish-infected grouper nervous necrosis virus (NNV) and selected antimicrobial peptides (AMP) by optical-readout-based microcantilever sensors. AMPs, the vital member in an innate immunity, can be promising candidates in the fight against pathogens or can exhibit other physiological functions by modulating immune response of infected cells. Grouper NNV which primarily cause mass mortality of many marine cultured fish species, and two selected AMPs in this study were found to inhibit viruses by agglutinating its virions to form aggregates. The binding affinity and kinetic rate constants of molecular recognition events calculated for NNV-AMP(TH1-5) compared to NNV-AMP(cSALF) were found to be 2.1-fold and 4.43-fold, respectively, indicating TH1-5 effectively bind with NNV more than cSALF. Therefore, the microcantilever biosensing technique provides a potential and useful screening of AMPs for affinity to NNVs.
In the study of signal transduction technique, the low-cost poly-Si TFT-embedded MCL is firstly reported. The comprehensive electrical investigation of current-voltage characteristics, transfer and low-frequency noise (1/f) characteristics was performed to further characterize the signal transduction under in-situ residual stress and externally compression stress for monitoring deflection. Meanwhile, the residual stress that was induced by inherent thin-film process variation resulted in a wide range of initial saturation drain currents, and the external compression stress for simulation of biomolecular recognition-induced surface stress mainly exhibited a small change in saturation drain current. As a result, coupled effect of electrical responses was found to be complex for measurement of biomolecular recognition.
The result of change in saturation drain current under external stresses showed the best sensitivity of 53 nA/μm. A comparable change of mobility and threshold voltage were also noticed about -1.58 cm2/V-s and -75 mV, respectively under the applied compressive bending of 50 μm. The decrease of both parameters indicates the resulting drain current change is the trade-off of mobility and threshold voltage. By 1/f noise analysis, the obtained current noise level of 1.34 nA is lower than the reported value for piezoresistive MOSFET noise. Also, interface trap generation tends to be reduced under highly compressive strain, while trap density change can be considered as negligibly small within the proper range of compressive loading. Moreover, MCL residual stresses that yield initial curvature may also induce an appreciable shift of initial saturation current due to the memorized strain effect. Therefore, this study demonstrated that the effect of varied residual stresses contributed to the sensor sensitivity can be successfully decoupled from that of external compression stresses by measuring the initial saturation current and maintaining the drain current-to-transconductance ratio. As a result of a linear correlation (correlation coefficients R>0.978) for sensor sensitivity with respect to the initial saturation current associated with the residual stress, this finding provides an approach for the TFT-embedded sensor calibration to suppress the device-to-device variation, enabling the potential of multiplexing array in the future.
Subjects
Microcantilever
Biosensor
Antimicrobial peptide
Nervous necrosis virus
Thin film transistor
Residual stress
Low-frequency noise
Performance discrepancy
Calibration method
SDGs
Type
thesis
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