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Authors = Marek Dawgul

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12 pages, 190 KiB  
Article
Optimization of a PVC Membrane for Reference Field Effect Transistors
by Chao-Sung Lai, Cheng-En Lue, Chia-Ming Yang, Marek Dawgul and Dorota G. Pijanowska
Sensors 2009, 9(3), 2076-2087; https://doi.org/10.3390/s90302076 - 19 Mar 2009
Cited by 9 | Viewed by 13484
Abstract
For the miniaturization of ISFET sensing systems,the concept of a REFET with low ion sensitivity is proposed to replace the conventional reference electrodes through the arrangement of a quasi reference electrode and a differential readout circuit. In this study, an ion-unblocking membrane was [...] Read more.
For the miniaturization of ISFET sensing systems,the concept of a REFET with low ion sensitivity is proposed to replace the conventional reference electrodes through the arrangement of a quasi reference electrode and a differential readout circuit. In this study, an ion-unblocking membrane was used as the top layer of a REFET. To optimize the REFET performance, the influences of the silylating process, different plasticizers, and the composition of the PVC cocktails were investigated. A low sensitivity (10.4 ± 2.2 mV/pH) and high linearity (99.7 ± 0.3 %) in the range from pH 2.2 to pH 11.6 was obtained for the REFET with a 60˚wt.% DNP/(DNP + PVC) membrane. To evaluate the long term stability, the drift coefficient was estimated, and for the best REFET, it was –0.74 mV/h. Two criteria for assessing the lifetime of REFETs were used, namely the increase in pH sensitivity to a value higher than 15 mV/pH and the degradation of linearity below 99 %. For the best REFET, it was approximately 15 days. Full article
(This article belongs to the Section Biosensors)
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6 pages, 191 KiB  
Article
Comparison of Urea Determination in Biological Samples by EnFETs Based on pH and pNH4 Detection
by Dorota G. Bijanowska, Marek Dawgul and Wladyslaw Torbicz
Sensors 2003, 3(6), 160-165; https://doi.org/10.3390/s30600160 - 29 Jun 2003
Cited by 11 | Viewed by 7479
Abstract
In this paper urea biosensors based on detection of pH and ammonium ions are presented. As transducers pH-sensitive ion-selective field effect transistors (ISFETs) and chemically modified FETs (ChemFETs) snsitive to ammonium ions were used.Results concerning urea determination by the bisensors in blood plasma [...] Read more.
In this paper urea biosensors based on detection of pH and ammonium ions are presented. As transducers pH-sensitive ion-selective field effect transistors (ISFETs) and chemically modified FETs (ChemFETs) snsitive to ammonium ions were used.Results concerning urea determination by the bisensors in blood plasma and in dialysate show that the biosensors can be applied for urea monitoring in the effluent dialysate. However in the case of pNH4 based EnFETs a special pre-treatment (dilution with tris/HCl buffer) of the samples is necessary. Full article
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14 pages, 382 KiB  
Article
An influence of polyHEMA gate layer on properties of ChemFETs
by Marek Dawgul, Dorota G. Pijanowska, Alfred Krzyskow, Jerzy Kruk and Wladyslaw Torbicz
Sensors 2003, 3(6), 146-159; https://doi.org/10.3390/s30600146 - 28 Jun 2003
Cited by 17 | Viewed by 8349
Abstract
A complex deposition procedure of the hydrogel layer of modified poly(2-hydroxyethyl methacrylate) (polyHEMA) covalently linked to the silicon nitride surface and covering only the gate area of the ISFET, was optimized for photolithographic technology, using standard silicon wafers of 3” diameter. The influence [...] Read more.
A complex deposition procedure of the hydrogel layer of modified poly(2-hydroxyethyl methacrylate) (polyHEMA) covalently linked to the silicon nitride surface and covering only the gate area of the ISFET, was optimized for photolithographic technology, using standard silicon wafers of 3” diameter. The influence of hydrogel composition and layer thickness on the sensors’ parameters was investigated. It was shown, that ISFETs covered with more than 100 μm thick polyHEMA layers in restricted pH-range could be practically insensitive to pH. Regarding mechanical stability of ion-selective sensors, a polyHEMA layer of ca. 20 μm thickness was found to be the best suitable for further manufacturing of durable ion selective sensors (Chemically modified Field-Effect Transistors – ChemFETs). The weak buffering properties of the thin polyHEMA layers had no disadvantageous influence on the sensors’ function. Full article
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