Microfluidics publications

FIGURE 10.1 An increase in microfluidics publications. A search was performed using the term microfluidics and the number of publications was graphed as a function of puhhcation year. The data shown represent the total number of journal articles (—), patents ( ) and the sum of both (—). 

The discovery of semiconductor integrated circuits by Bardeen, Brattain, Shockley, Kilby, and Noyce was a revolution in the micro and nano worlds. The concept of miniaturization and integration has been exploited in many areas with remarkable achievements in computers and information technology. The utility of microchips was also realized by analytical scientists and has been used in chromatography and capillary electrophoresis. In 1990, Manz et al. [1] used microfluidic devices in separation science. Later on, other scientists also worked with these units for separation and identification of various compounds. A proliferation of papers has been reported since 1990 and today a good number of publications are available in the literature on NLC and NCE. We have searched the literature through analytical and chemical abstracts, Medline, Science Finder, and peer reviewed journals and found a few thousand papers on chips but we selected only those papers related to NLC and NCE techniques. Attempts have been made to record the development of microfluidic devices in separation science. The number of papers published in the last decade (1998-2007) is shown in Fig. 10.1, which clearly indicates rapid development in microfluidic devices as analytical tools. About 30 papers were published in 1998 that number has risen to 400 in... 

Electrophoretic microfluidic chips feature a number of microreactor characteristics and have been used for conducting chemical and biochemical reactions in channels and microfabricated chambers, mixing reagents, microextraction and microdialysis, post- and preseparation derivatizations, etc. The most recent achievements are reviewed in Ref. 63 and other similar publications. These integrated microdevices perform PCR amplification, cell sorting, enzymatic assays, protein digestion, affinity-based assays, etc. In this section we describe such integrated microsystems and the most recent advances in this field. 

Future markets for biomedical microdevices for human genome studies, drug discovery and delivery in the pharmaceutical industry, clinical diagnostics, and analytical chemistry are enormous (tens of billions of U.S. dollars).In the following sections, major bioMEMS applications and microfluidics relevant to bioMEMS applications are briefly introduced. Because of the very large volume of publications on this subject, only selected papers or review articles are referenced in this entry. 

Figure I. Number of scientific articles citing the word microfluidics plotted as a function of the year of publication [ISl Web of Knowledge], The dashed line gives an exponential growth of the number of pubhcations in the years 1994 to —2002.

This short summary shows that there is the potential for many novel applications and improvements over the state-of-the-art within the above-mentioned criteria of sensitivity, cost, time, and size. However, despite a myriad of publications about microfluidic components, principles and applications, very few successful products with a relevant market share have emerged from this field so far. In the next chapter, we will outline probable reasons and present emerging paradigm changes for the future research in microfluidics. 

The first immunoassay performed in a capillary driven system was reported in 1978 [67]. Based on this technique, the commonly known over-the-counter pregnancy test was introduced into the market in the middle of the 80 s. Today, this microfluidic platform is commonly designated as a lateral flow test (LAT) [14]. Other terms are test strip , immunochromatographic strip , immunocapillary tests or sol particle immunoassay (SPIA) [68]. Astonishingly, hardly any publications from a microfluidic point of view or in terns of material classification exist, and apparently many company secrets are kept unpublished [69]. 

Finally, on-chip DNA quantitation will undoubtedly be an important feature of microfluidic sample processing for a number of different applications where the amount of input DNA for downstream genetic analysis is crucial. As discussed more extensively in Chapter 37, quantitative PCR (qPCR) methods in microfluidic systems have not been demonstrated to date. However, there are a number of publications describing real-time PCR in microdevices and it is likely only a matter of time before... 

The SMEC design was also optimized with regard to microfluidic properties by replacing the weir with a grid structure, in another publication (not included in this thesis) by Bergkvist et al. This improved design (Figures 49.14 and 49.15) was evaluated both numerically and experimentally. 

The shear amount of methodologies in the field of proteomics can be grasped by the fact that a topic search using the search words such as proteomics or proteome or proteomic in the Web of Science database returns 12081 publications (search done 2005-10-27). The huge amount of publications does by no means imply that there is no room for improvement. The application of microfluidics to proteomics analysis is still in its infancy and as the detection technologies becomes even more sensitive the ability to handle minute sample amounts will become paramount for continued progress. 

Public concern oti food safety has been raised in recent years due to the frequent reporting on the presence of toxic contaminants in food, in particular after the infamous incident of contamination in irrfant formirla and other dairy products by melamine deliberately added for economic gain. This gives rise to a sudden surge for request of analysis of contaminants in various food products and a rush to hospital by highly cOTicemed parents to demand for assurance that their babies who are the most vulnerable to melamine intoxication do not suffer related diseases. This leads to the second application of the microfluidic... 

As explained above, for most microfluidic applications, the electrical potential is zero at some distance slightly beyond the EDL region. This is not true for the case where the EDL overlaps, which is not considered in this entry. Interested readers are suggested to consult with some of the recent publications [9] for more details. Therefore, the boundary conditions specified in Eq. 17a can be extended to T = 0, T = 0, and... 

MR, Weigl BH (2006) Microfluidic diagnostic technologies for global public health. Nature... 

Since its first advent in 2002, the field of microfluidic fuel cells has stimulated many researchers, generating more than 100 scientific publications. Proof-of-concept microfluidic fuel cell devices have been demonstrated with various fuels such as hydrogen, methanol, formic acid. 

We recommend that readers consult other publications on microfluidic pumping for a comprehensive understanding of this topic. 

The publication authored by Venditti et al. [3] describes the results of an experimental investigation that attempts to characterize the influence of temperature on the zeta potential. The work describes the experimental procedure required to measure and classify the relationship between and temperature for a given liquid/substrate pair. It investigates this relationship for a number of buffer solutions conmuMily used in the microfluidics community. The influence of... 

Yager P, Edwards T, Fu E, Helton K, Nelson K, Tam MR, Weigl BH (2006) Microfluidic diagnostic technologies for global public health. Nature 442 412-418... 

So far there have been only a few publications on suspended microfluidics [28,45,46]. Below we examine the case of a spontaneous capillary flow in suspended microchannels with parallel, vertical walls. First, we theoretically derive the conditions for SCF onset using an approach based on the Gibbs free energy [4]. Next, we verify the onset of SCF using the Surface Evolver numerical program. The dynamics of the hquid motion is then analyzed, using analytical arguments based on a force balance between the... 

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