Lu Fang

Direct electron transfer glucose biosensor based on glucose oxidase self-assembled on electrochemically reduced carboxyl graphene

A glucose biosensor based on direct electron transfer of glucose oxidase (GOD) self-assembled on the surface of the electrochemically reduced carboxyl graphene (ERCGr) modified glassy carbon electrode has been reported. X-ray photoelectron spectroscopy (XPS) analyses of ERCGr indicate most of the oxygen-containing groups such as epoxy/ether groups and hydroxyl groups in the carboxyl graphene were eliminated, while carboxylic acid groups remained. GOD was immobilized on the ERCGr modified glassy carbon electrode via self-assembly. The cyclic voltammetric result of the electrode shows a pair of well-defined and quasi-reversible redox peaks with a formal potential of -0.467 V and a peak to peak separation of 49 mV, revealing that the direct electron transfer between GOD and the electrode has been achieved. The proposed biosensor exhibits a linear response to glucose concentrations ranging from 2 to 18 mM with a detection limit of 0.02 mM. Moreover, this facile, fast, environment-friendly and economical preparation strategy of ERCGr may be extended for the preparation of other graphene based enzyme electrode biosensors.

Comparative study of SAW temperature sensor based on different piezoelectric materials and crystal cuts for passive wireless measurement

As widely reported substrates for surface acoustic wave (SAW) temperature sensors, YX-cut quartz, YZ-cut LiNbO3 and 128°YX-cut LiNbO3 are selected to fabricate different one-port SAW resonator temperature sensors and comprehensive comparative studies of their performance and specifications are conducted carefully in this paper. Firstly, SAW sensors of each cut with 50 different layouts were designed and fabricated according to the calculated SAW velocity, and a general wireless measurement platform was setup. Secondly, under the same test conditions, Q factor, temperature sensitivity and decaying waves of these sensors were tested, and along with the calculated temperature coefficient of frequency (TCF), these parameters were finally compared respectively. After comparison, the conclusions are as follows: LiNbO3 sensors had higher temperature sensitivity, and showed superiority without the limitation of distance in wireless measurements, while quartz sensors performed well when the distance increased, and this suggests they can be applied to long distance sensing for their high Q factor even the sensitivity is moderate.

A novel implantable saw sensor for blood pressure monitoring

A novel implantable surface acoustic wave (SAW) sensor has been developed for blood pressure monitoring. The sensor is a wireless and batteryless microsystem composed of an SAW resonator, an oscillating circuit and an RF power converter. The total volume of the sensor is 1.9cm3 and the weight is 2.5g including its bio-compatible silicone coating. The sensitivity of the sensor is 1.75 KHz/mmHg. In vivo tests have been performed in a rat, showing the capability of the sensor for monitoring the blood pressure of small laboratory animals.

Study of the effect of fabrication conditions of porous gold electrodes on sensitivity of polymer-enzyme composite glucose sensors

Porous structures can increase sensor electrode surface areas and therefore increase their sensitivity. However there are few studies revealing the relationship between different fabrication conditions of porous structures on gold electrodes and sensitivity of glucose sensors based on glucose oxidase. Here a variety of amperometric glucose sensor electrode fabrication conditions such as surface rebuilding time, rebuilding potential pulse and platinization time have been studied. The conclusions are as follows: First, the sensitivity of the sensors increased with surface rebuilding time as a result of the formation of porous structures. Second, that the rebuilding potential pulse between -3V and 5V applied to the electrodes resulted in a maximal sensitivity. Third, platinization can increase electrode sensitivity obviously, but overlong platinization time will lower the sensitivity instead. These results will be useful for the fabrication of high sensitivity glucose sensors.