Sensors, microfabricated

In contrast to other analytical methods, ion-selective electrodes respond to an ion activity, not concentration, which makes them especially attractive for clinical applications as health disorders are usually correlated to ion activity. While most ISEs are used in vitro, the possibility to perform measurements in vivo and continuously with implanted sensors could arm a physician with a valuable diagnostic tool. In-vivo detection is still a challenge, as sensors must meet two strict requirements first, minimally perturb the in-vivo environment, which could be problematic due to injuries and inflammation often created by an implanted sensor and also due to leaching of sensing materials second, the sensor must not be susceptible to this environment, and effects of protein adsorption, cell adhesion, and extraction of lipophilic species on a sensor response must be diminished [13], Nevertheless, direct electrolyte measurements in situ in rabbit muscles and in a porcine beating heart were successfully performed with microfabricated sensor arrays [18],... 

Kordal, Richard Joseph, Arthur M. Usmani, Wai Tak Law, American Chemical Society, Division of Industrial and Engineering Chemistry, and American Chemical Society. Microfabricated Sensors Application of Optical Technology for DNA Analysis. ACS Symposium Series, no. 815. Washington, D.C. American Chemical Society, 2002. 

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. 

In this entry, we focus on the discussion of the platform technology for electrochemical sensors, metal oxide semiconductive (MOS) sensors, and piezoelectric based quartz crystal microbalance (QCM) sensors. There are other types of chemical sensors, such as optical sensors, Schottky diode based sensors, calorimetric sensors, field-effect transistor (FET) based sensors, surface acoustic wave sensors, etc. Information of these specific sensors can be found elsewhere and in current journals on sensor technologies. Because of the increasing importance of microfabricated sensors, a brief discussion of microsensors is also given. 

As in environmental analysis, for clinical analysis each sample is unique. A major problem for clinical analysis is sample collection, because immunore-actions can occur upon sample contamination. For this purpose, an automatic system for sample collection is required. In in vivo analysis the sample collection step is eliminated however, there are problems with sterilization of instruments. Therefore, it is recommended that for the best reliability of the analytical information, microfabricated sensor arrays that give the best responses be applied.35 36... 

V.V. Cosofret, M. Erdosy, T.A. Johnson, R.P. Buck, R.B. Ash, and M.R. Neuman, Microfabricated sensor arrays sensitive to Ph and for ionic distribution measurements in the beating heart. Anal. Chem. 67,1647-1653 (1995). 

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 is one of the common trends in science and technology of our age, since microfabricated sensors will play indispensable roles for the construction of very small, sophisticated instruments as well as the microinstrumentation of analytical tools ( ) ... 

---