What is TFT?
The concept of Thick Film Technology (TFT) involves developing requisite structures on substrates using screen printing technology. Structures are printed by forcing the paste, which contains the main ingredient (metals like gold, silver etc. or non metals such as graphite, glass and ceramic), and some binding material through a screen mesh onto a substrate (alumina, plastics etc.). During the curing process the binding material evaporates and structures from the requisite material is formed. Control of the printing allows the preparation of precisely defined and homogeneous shapes / structures.

What is an electrode?
An electrode is a conductor on the surface of which the electrochemical reaction takes place. It is also, a system in which a conductor is in contact with a mixture of oxidised and reduced forms of some chemical species. Usually it is in the form of a wire, rod, or plate. Electrodes are made of metal, e.g., copper, lead, platinum, silver and zinc or from a non-metal, commonly carbon.

What is an electrochemical sensor?
A classical electrochemical cell / sensor consists of a small glass cell body often jacketed by a thermostatic circuit, which is clamped to a plastic top with ports for electrodes, gas purge tube and thermometer. The electrochemical measurement is based on observation of the processes occurring at the electrode surfaces with the working electrode measuring the electrode processes, the reference electrode establishes the reference potential and the last one, i.e. the auxiliary electrode, creates a current loop and prevents the potential drop between the working electrode and the reference electrode.

What is a biosensor?
A biosensor is a device that converts the biological activity into a quantifiable signal. Biosensors have their origin in work carried out by L.C. Clark and Lyons on the combination of enzymatic actions with polarographic, potentiometric or conductometric electrodes, which resulted in a new field of electroanalytical biochemistry.

What is a screen printed (TFT) electrode / sensor / biosensor?
The entire classical electrode system can be miniaturised and integrated as an electrochemical sensor using thick film technology. The sensor is formed by screen printing the 3-electrode system onto a substrate i.e. working, reference and auxiliary electrodes. At the end of the sensor there is a contact field connected to the active part by silver conducting paths covered with a dielectric protection layer. TFT biosensors with mediators, immunosensors, amperometric biosensors etc. are created by immobilising suitable substances on the sensor substrates.
What are the applications in which TFT sensors can be used?
All applications based on electrochemical and electro-analytical techniques involving electrode process measurements can be catered for by TFT sensors. The practical applications have a very high significance in the scientific community, medical and pharmaceutical industries, environmental monitoring etc. Some of the examples include environmental pollutant analysis, compound toxicity analysis, trace analysis, detection of different compounds in human blood and urine etc. Based on specific applications different types of TFT based sensors have been developed such as displacement sensors, pressure and temperature sensors, accelerometers and gas sensors, electrochemical sensors and substrates for biosensors.

Do we need any special equipment for using TFT sensors?
No special equipment is needed as these sensors can be very easily integrated into the classical arrangement. A few accessories, necessary for connecting the sensors to the measurement equipment, are available from BVT. However, to remove some of the conventional problems of the classical measurement techniques which use external stirrers etc., BVT have also developed a micro flow system. This system has an internal pump for stirring and mixing the cell contents and a special chamber for sensor placement.

How can the response of the TFT sensors be quantified and analysed?
Using BVT standard connectors the response of the TFT sensors can be directly measured and analysed using standard polarography equipment. Other data acquisition equipment is also available and will allow direct observation and analysis of results on a PC. The BVT biosensor analyser has a memory capacity which allows usage of these sensors in actual field conditions.

What is the sensitivity, range and accuracy of the TFT sensors?
The sensitivity of a TFT sensor depends on the application. In most common applications the range lies between 1µM - 10 mM. There are some sophisticated methods which allow detection in pM range. The accuracy is highly dependent on the accessories used. Using precise thermostating correction to external influences precision up 0.01 % can be achieved. The whole system error lies within a range of 1 - 5 %.

Are the results obtained from the TFT sensors repeatable?
Each of the TFT sensors can be individually calibrated and used for a few measurements with a very high repeatability. The low cost of the sensor allows disposability of the sensor after a few uses. Sensor response value may however vary slightly change between different production batches.

What is the long term reliability of TFT sensors?
BVT tests show that these sensors are not affected at all in short term period of months. Periods spanning a few years show only a very slight decrease in their sensitivity.

What is the range or type of electrode materials available in TFT sensors?
All standard metals such as gold, silver, platinum and non-metals such as graphite as well as as silver / silver chloride are available as electrode materials in TFT sensors. Due to the availability of a wide range of TFT pastes, TFT sensors with different combinations, customised to specific user needs, can be produced.

Are TFT sensors much more expensive than the conventional sensors?
The TFT sensors are extremely low cost and can be disposed of after a few uses.

Can we request different combinations of electrode materials?
BVT will be pleased to prepare sensors based on specific user requirements.

Can we request specific sensor structure development for our applications?
Major markets for BVT sensors are the research and development sector. Customisation of existing products and new product development form the core part of our offer to clients.
Where can we request more information on BVT TFT sensors, accessories and other related products?
Downloadable files are available for your reference in the Products Section of this web site - www.bvt.cz. Should you require any further clarification please use the info@bvt.cz e-mail address. We will be pleased to send you our response on a priority basis.

Where can we obtain prices and place orders for TFT sensors?
You may request prices on the info@bvt.cz e-mail address. Our product forms for both standard products and new products are available for download within the Products Section of the web site - www.bvt.cz.