Silicon chip laboratories

The chip laboratories also present some difficulties not found in macroscopic laboratories. The main problem concerns the large surface area of the capillaries and reaction chambers relative to the sample volume. Molecules or biological cells in the sample solution encounter so much wall that they may undergo unwanted reactions with the wall materials. Glass seems to present the least of these problems, and the walls of silicon chip laboratories can be protected by formation of relatively inert silicon dioxide. Because plastic is inexpensive, it seems a good choice for disposable chips, but plastic also is the most reactive with the samples and the least durable of the available materials. 

The first solid-state transistor was made not from silicon but from the element below it in the Periodic Table germanium. This substance is also a semiconductor, and can be doped in the same way. William Shockley, Walter Brattain, and John Bardeen devised the germanium transistor at Bell Telephone Laboratories in New Jersey in 1947. It was a crude and clunky device (Fig. VJa) - bigger than a single one of today s silicon chips, which can house millions of miniaturized transistors, diodes, and other components (Fig. Vjb). The three inventors shared the Nobel Prize in physics in 1956. 

The first prototype transistor (a point-contact semiconductor amplifier ), built by Bardeen and Brattain at Bell Laboratories in 1947 (a), is a far cry from today s silicon chips, packed with miniaturized semiconductor components (6)... 

It has been mentioned already that there are different levels of sophistication with regard to the involvement of computer applications in GLP studies and test facilities. These levels may range from the complex problems involved in the GLP compliant management of computer networks and of laboratory information management systems (LIMS) to the question of whether a simple instrument controlled by a built-in, pre-programmed chip should be treated in the same, extensive way with regard to software validation . It is certainly self-evident, as these two examples demonstrate, that not all types of IT applications have to be considered as equal with regard to GLP compliance it may indeed be impossible to do so. As it is commonplace nowadays that the silicon chip penetrates the operation of practically all kinds of work, the elucidation of its involvement in the operations of test facilities becomes an essential part of the implementation of GLP. 

A current research project in our laboratory deals with the development of miniaturized FIA systems with the final goal of constructing a complete system by micromachining. The calorimetric measuring principle has been found to work surprisingly well in these small devices. Encouraging results have been obtained with various silicon chip test structures [36]. 

In this section, we describe two pixel options which are being considered hybrid pixel arrays in which the readout electronics and the silicon detector array are constructed as two separate silicon chips that are then bump-bonded together, and the monolithic pixel detector in which the readout electronics is on the same substrate as the silicon detector. R D for both technologies is currently being pursued for potential use at the SSC laboratory. 

Figure 7.3. The evolution of electronics a vacuum tube, a discrete transistor in its protective package, and a 150 nun (diameter) silicon wafer patterned w ith hundreds of integrated circuit chips. Each chip, about I enr in area, contains over one million transistors, 0..35 pm in size (courtesy M.L. Green, Bell Laboratories/Lucent Technologies).

Sample integrations similar to pharmaceutical approaches were already examined in 1997 [39]. Here, a chip-like microsystem was integrated into a laboratory automaton that was equipped with a miniaturized micro-titer plate. Microstructures were introduced later [40] for catalytic gas-phase reactions. The authors also demonstrated [41] the rapid screening of reaction conditions on a chip-like reactor for two immiscible liquids on a silicon wafer (Fig. 4.8). Process conditions, like residence time and temperature profile, were adjustable. A third reactant could be added to enable a two-step reaction as well as a heat transfer fluid which was used as a mean to quench the products. 

We reduced this concept to practice by developing a microfluidic system in collaboration with the Research Laboratory of IBM in Ruschlikon, Switzerland. The chip component of this system is depicted in Figure 6. On a silicon substrate, a number of capillary systems are etched. Each one consists of a fill port that allows... 

Other than the standard cross-t configurations, electrophoretic microchips are not currently commercially available and tend to be fabricated in the laboratories that use them. They can be constructed from glass (Pyrexlike or soda lime), silicon (as per microelectronic chips), or a variety of plastics, or cast from silicone-like materials (polydimethyl-siloxane). The first two of these constitute the vast majority of the electrophoretic devices described in the literature. 

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