Universal signal conditioning system for electrochemical and bioluminescent sensor arrays

Abstract

Sensors are devices widely used in all areas of activity, from the cars on the roads to the implanted sensors in animal bodies and more recent in human bodies. Life cannot be imagined without sensors. In the last decade, new principles of sensors emerged, sensors that use more than one principle to detect and quantify a phenomenon. Sensors that use living cells, biotic elements such as mammalian cells, bacteria, and living tissues are relatively new. Moreover, applying biotic materials, whole cell biosensors started to be discovered and implemented. These types of sensors have the capacity to perform more than one task at a time, from detection, measurements (usually based on more than one type of reaction) and quantification of the reactions. The author focussed his research on developing a new signal conditioning system able to work with both electrochemical and bioluminescent sensors array. This work presents a new signal conditioning system for electrochemical and bioluminescent sensors array. The system is able to work with both kinds of amperometric sensors, amperometric sensors which inject and subtract current from and into circuits. This property makes the system a universal signal conditioning system for amperometric sensors. The bases of the research are the electrochemical sensors designed at Tel Aviv University by Prof. Yosi Shacham and his team. The main problems encountered during the three- year research in the field was the novelty of the biological and electrochemical fields that the author needed to know so as to be able to design the system. The signal conditioning system is able to work with a quite large field of currents, from several hundreds of micro amps to several hundreds of nano amps. Another contribution of the author presented in this thesis is a new and simplified operational transductance amplifier (OTA) that is able to work maintaining the integrity and the functionality in the parameters that the author established. The research led to the implementation of an original equivalent schematic for the simulation of electrochemical sensors. There are in the specialised literature several approaches for an equivalent electronic design for electrochemical cells, from the simplest which do not emulate the major components of the real 3 electrode cell to the complex designs that emulate even the biological and electrochemical noise presented by the sensors. The design one should chose is closely related to the application needed. The author implemented an original design for an 8X8 electrochemical sensor array with applicability in the simulation and in the experimental field. The research that the author conducted presents a great step forward in the investigated field. From this point, the circuits can be improved furthermore to accept a wider variety of sensors. Because of the temperature compensation block, the signal conditioning system is able to work with lower signal than the signals we have used in this research. The principle used for temperature compensation is also a novelty in this type of signal conditioning systems, the errors being eliminated by modifying the integrating capacity of the operational transducer amplifier in a proportional manner with the modification of the temperature. Moreover, the sensor array can be enlarged to more than 128 sensors. The author managed to design a new concept using relatively low complexity circuitry so as to maintain the number of integrated parts as low as he was able to.