Microfabricated sensors, development

In the past decade, microfabrication methods developed in the microelectronic industry have led to new opportunities for device research and development involving chemically sensitive electronic structures. In 1980, this subject was reviewed in depth at a NATO Advanced Study Institute (1). Over the last five years, there have been three international conferences 2-k), devoted to sensors with a strong emphasis on chemical sensors as well as a number of national and specialized meetings on the subject (5,6). In this paper, some recent developments that will have long term consequences on the study of chemically sensitive electronic devices will be reviewed. To simplify the discussion, the topics are divided into the following categories ... 

Davis G. Microfabricated sensors and the commercial development of the i-Stat point-of-care system. In Ramsay G, ed. Commercial Biosensors. New York John Wiley Sons, 1998 47-76. 

The use of a graphite electrode, particularly glassy carbon, is also relatively limited in microfabricated electrochemical sensors. However, thick-film silk-screened graphite electrodes have been used in chemical sensor development, and the use of carbon fiber in microsensor applications has been reported. The purity of the graphite ink for thick-film silk screening is very critical to the performance of the sensor. 

The incorporation of these new spectroscopies into a laboratory-on-a-chip will be essential for adequate selectivity.Considerable progress has been made toward the development of microfabricated sensor arrays, where each element in the array is capable of its own preselected detection event, but the technology is not sufficiently robust to place into field operation. ... 

Microfabrication technology has made a considerable impact on the miniaturization of electrochemical sensors and systems. Such technology allows replacement of traditional bulky electrodes and beaker-type cells with mass-producible, easy-to-use sensor strips. These strips can be considered as disposable electrochemical cells onto which the sample droplet is placed. The development of microfabricated electrochemical systems has the potential to revolutionize the field of electroanaly-tical chemistry. 

Recent developments in microsystems technology have led to the widespread application of microfabrication techniques for the production of sensor platforms. These techniques have had a major impact on the development of so-called Lab-on-a-Chip devices. The major application areas for theses devices are biomedical diagnostics, industrial process monitoring, environmental monitoring, drug discovery, and defence. In the context of biomedical diagnostic applications, for example, such devices are intended to provide quantitative chemical or biochemical information on samples such as blood, sweat and saliva while using minimal sample volume. 

All of the above trends make a planar platform configuration the ideal choice for the development of such sensors due to the compatibility of this geometry with a range of microfabrication technologies, the availability of low-cost materials for the production of such platforms and the robust nature of planar configurations when compared with alternatives based on optical fibres. 

The third microhotplate introduced in Sect. 4.3 was designed to extend the operation temperature limit imposed by the CMOS-metallization contacts in the heated area. A new heater design was devised, and a microfabrication sequence that enables the realization of Pt temperature sensors and Pt-electrodes was developed. This microhotplate was also monolithically integrated with circuitry as presented in Sect. 5.2, and operating temperatures of up to 500 °C have been achieved. 

Many of the devices that have thus far been envisioned as products of nanotechnology (e.g., nanoscale environmental sensors, information processors. and actuators) cannot be produced by the large-scale microfabrication techniques currently in use. The further development of nanotechnology hinges on the understanding and manipulation of physical laws and processes at the nanometer level, such as electronic, interatomic, and mter-molecular interactions that can be manipulated lu allow efficient assembly of nanostructures. 

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