Screen-printing technology, disposable

The possible use of graphite-epoxy material by screen-printing technology opens the possibility of mass production of disposable sensors for heavy-metal analysis using stripping techniques. The utilization of these sensors for an extensive application in real heavy-metal samples is underway in our laboratories. 

Electrochemical sensors and biosensors offer the achievable opportunity of simplifying the analyses of complex matrices, outside of the laboratory, by suitable modification of appropriate electrode materials [1-5]. One of the most attractive methods for the fabrication of such devices involves the use of screen-printing technology. This allows the (bio)sensors to be manufactured in a wide range of geometries at low cost, particularly when carbon is used therefore, this allows the devices to become disposable [1,2]. A typical screen-printed electrode design commonly used in our laboratories for prototype investigations is shown in Fig. 23.1. 

Electrochemical analytical methods, particularly polarography and voltammetry rise in the 1960s was caused by the demand in trace analysis and new technique of preliminary electrochemical concentration of the determined substance on the electrode surface [1,2]. The reason for the new renaissance is the use of screen-printed technologies, which resulted in creation of new electrodes so cheap that they can be easily disposed and there is no need of regenerating the solid electrode surface [3]. 

Most biosensors based on AChE have the enzymes immobilized on the surface of the sensor. The inhibition reaction being irreversible, the membrane with immobilized enzyme has to be replaced after several measurements or the biosensor can be use for only one determination. Due to this fact, the researchers tried to realize pesticide biosensors with a renewable surface or disposable biosensors based on screen-printed electrodes (SPE). The screen-printing technology provides a simple, fast and inexpensive method for mass production of disposable biosensors for different biomolecules starting with glucose, lactate and finishing with environmental contaminants as pesticides (Kulys et al., 1991) and herbicides (Skladal, 1992). 

An important particularity with inhibition assays is that when this is an irreversible inhibition, it forces the use of disposable biosensors that may be prepared, e.g. by screen-printing technology, and the whole application relies then on the reproducibility of manufacture of different devices [70]. 

Most electrochemical immunosensors use screen-printed electrodes produced by thick-film technology as transducers the importance of screen-printed electrodes in analytical chemistry is related to the interest for development of disposable and inexpensive immunosensors. A thick-film is based on the layers deposition of inks or pastes sequentially onto an insulating support or substrate the ink is forced through a screen onto a substrate and the open mesh pattern in the screen defines the pattern of the deposited ink. 

The first miniaturized electrochemical device for measuring glucose in whole blood was a mediated system produced in thick-film technology by screen printing [73]. This disposable, single-shot system is produced and actually marketed widely by the company Medisense. Several other companies are now following with similar approaches [74,75]. 

Applications of electrochemical transducers have relied on conventional and bulky disk (C, Au) or mercury drop electrodes, as well as on mass-producible, single-use, thick-film carbon screen-printed electrodes. The sensitivity of such devices, coupled to their compatibility with modern microfabrication technologies, portability, low cost (disposability), minimal power requirements, and independence of sample turbidity or optical pathway, make them excellent candidates for DNA diagnostics. In addition, electrochem-... 

An important aspect in the development of sensor technology is the need for mass-produced and low-cost disposable transducers [48]. This is especially relevant for environmental and biomedical analysis. For electrochemical sensors, screen-printed electrodes fulfill this need, and the ease of preparation and low cost of MIPs make them attractive as recognition elements for such devices. A first report on this topic demonstrated that an imprinted polymer could be coated onto screen-printed carbon electrodes, and the resulting devices could be used as an amperometric sensor [33]. 

As it has been shown in previous sections, the use of screen-printed electrodes as support for genosensor devices offers enormous opportunities for their application in molecular diagnosis. The technologies used in the fabrication of these electrodes allow the mass production of reproducible, inexpensive and mechanically robust strip solid electrodes. Other important advantages of these electrodes are the possibility of miniaturization as well as their easy manipulation in a disposable manner and therefore the use of small volumes, diminishing the cost of the analysis. This is an important issue that makes this methodology for the detection of DNA more attractive. 

Challenges facing the development of in vitro amperometric biosensors (interference rejection, rapid response, reproducibility, response range) have been met in many cases, and commercially available devices based on disposable test strips that incorporate miniature two-or three-electrode electrochemical cells are available for a variety of analytes (see Sect. 10.3.7). Thin-fihn and thick-film technology [80] have been used to mass-produce reproducible sensing elements, and amperometric detection in oxidase-based devices occurs by peroxide oxidation or the oxidation of freely diffusing mediators such as ferricyanide and ferrocene derivatives. The screen-printing process for disposable sensor preparation has also been reviewed [144]. 

Laschi, S., Palchetti, L, Mascini, M., 2008. Disposable screen printed electrochemical sensors and evaluation of their application as alarm systems against terrorism. In Lechnga, L.M., Milanovich, F.P., Skladal, R, Ignatov, O., Austin, T.R. (Eds.), Commercial and Pre-commercial Cell Detection Technologies for Defence against Bioterror. lOS Press, Amsterdam, Netherlands. 

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