Sensors

473 KiB

Open AccessArticle

Sensors and Asymptotic w-observer for Distributed Diffusion Systems

by R. Al-Saphory and A. El Jai

Sensors 2001, 1(5), 161-182; https://doi.org/10.3390/s10500161 - 27 Oct 2001

Cited by 9 | Viewed by 9938

The aim of this paper is to study the regional observer concept through the consideration of sensors. For a class of distributed diffusion systems, we propose an approach derived from the Luenberger observer type as introduced by Gressang and Lamont [1]. Furthermore, we show that the structures of sensors allow the existence of regional observer and we give a sufficient condition for each regional observer. We also show that, there exists a dynamical system for diffusion systems is not observer in the usual sense, but it may be regional observer. Full article

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880 KiB

Open AccessArticle

Evaluation of Protein Adsorption on Chitosan Surfaces with Reflectometry Interference Spectroscopy

by Xiao Ying Lü, Yan Huang and Chao Qun Ma

Sensors 2001, 1(5), 148-160; https://doi.org/10.3390/s10500148 - 12 Oct 2001

Cited by 10 | Viewed by 11414

Abstract

Using a biomedical sensor setup RIfS we have investigated the kinetic behavior of human albumin (Alb), human fibrinogen (Fib), and human immunoglobulin G (IgG) adsorbed onto surfaces of chitosan. Polystyrene (PS) was used as the control material in this study. The optical thickness of three kinds of proteins measured by RIfS was related to their molecular dimensions and potential orientations on a film surface. According to the operation principle of RIfS and the molecular dimensions of three kinds of proteins, the adsorbed layers of proteins onto the surface of chitosan and PS was calculated by using a newly introduced equation. The microstructure of the chitosan and polystyrene film and the surfaces with adsorbed proteins were imaged by atomic force microscopy (AFM). With AFM analyses the lateral distribution of the protein molecules on surfaces have been recognized. The results show that the number of adsorbed layers of the three proteins on the surface of chitosan are 0.635 for Alb, 0.158 for Fib and 0.0967 for IgG, and of polystyrene are: 0.577 for IgG, 0.399 for Fib, 0.336 for Alb. This study confirmed that RIfS is a useful tool for the analysis of plasma proteins adsorbed on a surface of biomaterials. Results show that at first on the surface of chitosan film much more Alb than Fib was adsorbed which demonstrated that chitosan has a antithrombus function. Secondly, on the surface of chitosan film more Alb and less Fib were adsorbed than on the surface of PS film, which demonstrated that chitosan has a better blood compatibility than polystyrene. Thirdly, the calculated layer number of the three proteins indicated that on both chitosan and PS substrates monolayer coatings form. Full article

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97 KiB

Open AccessArticle

Magnetism-Based Remote Query Glucose Sensors

by K. G. Ong, M. Paulose, M. K. Jain, D. Gong, O. K. Varghese, C. Mungle and C. A. Grimes

Sensors 2001, 1(5), 138-147; https://doi.org/10.3390/s10500138 - 7 Oct 2001

Cited by 22 | Viewed by 9715

Abstract

Two wireless, passive remote query magnetism-based glucose sensors, which operate in combination with a mass and volume changing glucose responsive polymer, are presented. One sensor design is based upon the magnetostatic coupling of magnetically soft thin-film elements; as the polymer volume changes in response to glucose concentration so does the magnetostatic coupling between elements. In response to a time varying magnetic field, upon reversal of the magnetization vector of the elements the magnetostatic coupling determines the time rate of change of magnetic flux, and hence the amplitude of the voltage spike generated in a pick-up coil. The other sensor consists of a free-standing magnetoelastic thick-film, coated with a thin layer of the glucose responsive polymer. In response to a time varying magnetic field the sensor mechanically vibrates at a characteristic resonant frequency; the characteristic resonant frequency of the sensor linearly tracks the change in mass of the glucose responsive polymer. Full article

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Sensors, Volume 1, Issue 5 (October 2001) – 3 articles , Pages 138-182

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