An Amperometric Glucose Biosensor With Enhanced Measurement Stability and Sensitivity Using an Artificially Porous Conducting Polymer

A conducting polymer [polypyrrole (PPy)]-based amperometric biosensor fabricated on a platinum-coated nanoporous alumina electrode has been described. This fabricating process introduced artificial porosity into the PPy film, and the template pore sizes were carefully chosen to match the size of the glucose oxidase (GOx) molecule. The $hbox{PF}_{6}^{-}$-doped PPy film was synthesized with 0.05 M pyrrole and 0.1 M $hbox{NaPF}_{6}$ at a current density of 0.3 $hbox{mA/cm}^{2}$ for 90 s. Immobilization was done by physically adsorbing 5 $muhbox{L}$ of GOx on the nanoporous PPy film. Glutaraldehyde (0.1 wt.%, 5 $muhbox{L}$) was used for cross-linking. The synthesized films were characterized by using an electrochemical technique and scanning electron microscopy (SEM). Amperometric responses were measured as a function of different concentrations of glucose at 0.4 V. Nanoporous electrodes lead to high enzyme loading, whereas the use of a cross-linking agent increased stability, sensitivity, reproducibility, repeatability, and shelf life.      

A simple interface circuit to measure very small capacitancechanges in capacitive sensors

This paper presents an easy-to-design interface circuit to measure very small-percentage capacitance variations in capacitive sensors, especially suitable for industrial measurements. A computer-controlled 24-bit A/D converter is employed to obtain a higher resolution. This interface circuit can be used with various types of capacitive sensors. The most interesting thing is, that the measurement results through this interface circuit are independent of the initial capacitance of the sensor. In addition, the double differential operating principle used here minimizes the error caused by coupling and stray capacitance of sensor probes. The operating principle of the designed interface circuit, the major assumptions made, test data, and possible future developments are discussed     

SAW Sensor Network Fabricated on a Polyvinylidine Difluoride (PVDF) Substrate for Dynamic Surface Profile Sensing

A combination of two 2-D sensor networks is proposed as a dynamic surface profile sensor network for biomimicing applications. A surface acoustic wave device fabricated on a polyvinylidine difluoride substrate has been investigated as the elementary 1-D bending curvature sensor used in the network. The device was tested under an injected signal and it shows the variation in amplitude and phase angle of output signal with respect to the injected signal in response to the bending curvature. These dual outputs provide opportunity to make an intelligent sensor with self error limit determination capability. Finally, a network of such sensors is proposed as a dynamic surface profile sensor