CIRCUITS AND DEVICES FOR SENSOR NETWORKS AND SYSTEMS
The main objective of the activity is the development of the necessary technologies for future sensors and sensor systems. In the context of this objective, the research targets the development of Bio-, Chemical and Physical sensors as well as sensor readout, wireless telemetry and RF remote powering in the near and the far field.
A. Bio- and chemical sensors
A1. Bio- and chemical sensors
The detection of different DNA mutations in a fast and easy way is increasingly important in disease screening. Towards this end, micromechanical capacitive biosensors have been developed and their operation verified in the detection of the biotin–streptavidin interaction, the detection of the CD19 mutation in beta-thalassemia and the detection of Pb2+ ions in water. Using the experience gained, this work now focuses on developing novel graphene/graphene oxide sensors for biological and chemical sensing.
A2. Sensor readout
For the readout of the biosensor array an embedded system has been developed and implemented into a programmable IC (FPGA) in cooperation with the Electronics Dept of TEI of Pireas. It comprises a subsystem able to convert capacitance changes into frequency changes and allows for the embedding of a NIOS processor. The system is intended to be used in portable, processing-power hungry sensor applications such as identification of complex odors with an electronic nose and point of care diagnostics devices which require the fast processing of the input signal of biosensor arrays. Moreover, it is highly versatile as the FPGA may be easily reprogrammed to add new functions and adapt to a sensor array with different characteristics and sensor population.
B. Physical Sensors
I. Graphene Nano Platelets/PDMS nanocomposite strain sensors
Carbon-based materials are commonly used as fillers in polymer matrices for the fabrication of flexible physical and chemical sensors. Amongst carbon materials, graphene has emerged as a promising next generation material replacing the traditionally used carbon black. In this work, we develop a fabrication process for a graphene nano platelets/polydimethlylsiloxane (GNP/PDMS) capacitive strain sensor.
To build the sensor a simple fabrication process has been developed, where two PDMS films are used as substrate (bottom) and shielding (top) layer of the sensor. The conductive polymeric nanocomposite is placed between the PDMS layers by spin-coating, whilst copper tape is used to conduct the GNP/PDMS composite.
C. RF harvesting and passive sensor tags
RF power-harvesting systems are of particular interest in autonomous sensor tag design because of their ability to draw power from electromagnetic fields generated by controlled and stable RF power sources. RF sensor tags are based on the technology of RF identification systems which are widely used in product chain applications. A variety of real-time monitoring applications such as structural health monitoring in large structures, often require the deployment of such remotely powered sensor tags. In this case the tags are often installed in inaccessible places or integrated in the monitored structure during construction. In this work, following the development of a power-harvester with an embedded antenna operating at the 430 MHz band capable of operating near ground or metal planes, a new PIFA antenna and harvester were developed for operation at 2.5GHz. A prototype embedded within the PCB of an autonomous RFID tag vas validated by measuring its return loss, efficiency, and radiation patterns at the operation frequency band.