The Elimination of Temperature Effects on a Piezoresistive Microcantilever Biosensor
Date Issued
2009
Date
2009
Author(s)
Ku, Yu-Fu
Abstract
In this study, polycrystal silicon piezoresistive material is being designed and discussed for electro-mechanical transduction. Utilizing MEMS and semi-conductor ion doping technologies, this work demonstrates design, fabrication and integration of a piezoresistive microcantilever embedded in a microfluidic channel chip system with a Wheatstone Bridge to transfer mechanical bending into electrical voltage for output. Also, the microprobe and spectrum analyzer were introduced for the detection of Gauge factor and noise measurement in the piezoresistive microcantilever biosensor.n a conventional configuration of double-beamed microcantilever systems, the distinctive surfaces of sensing and reference free-standing cantilever beams yield independent signal outcome due to the effect of pH values in solution. In this study, the single free-standing microcantilever is chosen for detection in biochemical environments. However, the single free-standing microcantilever was significantly affected by a temperature change of about 25.73 μV/0C, which failed to be practical in application. Those are attributed to the temperature coefficient of resistance (TCR) and bimorph effect of multiple layers of distinctive materials, in which TCR has approximate 10 times in noise signal far larger than that of bimorph effect. The independence of TCR and bimorph effect still remains unsolved by the most commonly used Wheatstone bridge electrical circuit configuration of the current state of art. Therefore, a novel self thermal deduction by a temperature feedback approach is firstly developed for the piezoresistive microcantilever to eliminate temperature-induced noise and to achieve high performance. tilizing the fixed polysilicon resistance on chip as temperature sensor to obtain temperature T allows calculation and obtains relation between fixed and cantilever resistances for temperature feedback. Accurate temperature feedback has been proved available under large-scale temperature difference. Furthermore, the detection of C-reactive protein antigen was achieved without bulky temperature control devices. The surface stress induced by C-reactive protein antibody-antigen binding was measured with the elimination of microcantilever thermal-sensitive effect by the feedback apporoach. This approach has proven the feasibility of piezoresistive microcantilever and this system.
Subjects
Surface stress
Piezoresistor
Cantilever
Bimorph effect
TCR
Type
thesis
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