Paper microfluidic devices

The various sample preparation methods mentioned in Section 5.6 have been tried in microfluidic devices off-line for biological and environmental matrices followed by analysis of the extracted samples by NLC and NCE. The available papers in the literature on this subject are discussed in the following sections. 

The membrane technology has been tested in microfluidic devices. Normally a membrane is mounted between two chips, which make a microchannel, and fluid is allowed to pass through the membrane channel. Some papers are available on this method, which are discussed here. Hisamoto et al. [61] reviewed the application of capillary assembled microchips on PDMS as an online... 

Sample preparation in NLC and NCE is the most important step in analysis due to the nano nature of these modalities. The sampling should be carried out in such a way as to avoid changes in the chemical composition of the sample. The quantitative values of species depend on the strategy adopted in sample preparation. Extraction recoveries may vary from one species to another and they should, consequently, be assessed independently for each compound as well as for the compounds together. Materials with an integral analyte, that is, bound to the matrix in the same way as the unknown, which is preferably labeled (radioactive labeling) would be necessary, which is called method validation. As discussed above few papers described off- and online sample preparation methods on microfluidic devices. Of course, online methods are superior due to lower risk of contamination and error of methods. Not much work been carried out on online nanosample preparation devices, which need more research. Briefly, to get maximum extraction of analytes, sample preparation should be handled very carefully. 

In living organisms, each cell produces thousands of proteins and one set of these proteins is called a proteome. Their analysis is a tedious job. Moreover, the low amounts of proteins in a proteome makes this task challenging. Fortunately, the development of microfluidic devices including NCE is the best innovation of the last decade to solve such types of riddles. Many papers have been published on proteomics analysis using NCE some... 

Contrary to conventional HPLC, almost 98% of chiral resolution in CE is carried out using the chiral selector as a mobile phase additive. Again all the common chiral selectors used in NLC can also be used in NCE. But, unfortunately, few chiral molecules have been tested in NCE for enantiomeric resolution of some racemates. To the best of our knowledge only cyclodextrins and protein-based chiral mobile phase additives have been used for this purpose. Manz and coworkers discussed chiral separations by NCE in their reviews in 2004 [21] and 2006 [22], Later on, Pumera [16] reviewed the use of microfluidic devices for enantiomeric resolutions in capillary electrophoresis. Not much work has been carried out on chiral resolution in NCE but the papers that are available are discussed here. 

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... 

A series of papers have concerned the incorporation of various sensors into lab-on-a-chip devices with, for example, conductivity measurements being combined with poly(methyl methacrylate) microfluidic devices to analyse mixtures of mono- and polyanionic molecules such as proteins [148]. 

Next, consider fully developed flow in a narrow channel, which is typical of a microfluidic device. Figure 8.12 shows the normal view, with flow going into the paper. The velocity varies in x and y according to the equahon ... 

As seen in this brief chapter, the direct-printing process, based on laser printing of layouts on polyester films or wax paper, has the potential to become a powerful technology for the rapid prototyping of microfluidic devices at very low cost, and even a source of low-cost production of disposable devices. This is supported by the fact that the required instrumentation is commonly found at offices and chemistry laboratories. Besides the typical injection and separation channels for electrophoresis, this technology has shown that mixing, preconcentration, clean-up, reactor devices. 

Martinez AW, Phillips ST, Whitesides GM (2008) Three-dimensional microfluidic devices fabricated in layered paper and tape. Proc Natl Acad Sci U S A 105(50) 19606-19611... 

Paper-Based Sensors and Microfluidic Chips, Table 2 Summary of typical detection methods and target analytes for paper-based microfluidic device and paper-based microarray plates (Reprinted with permission from Li et al. [1]. Copyright [2012], American Institute of Physics)... 

Paper-based microfluidic device Colorimetric detection Glucose, protein (e.g., bovine serum albumin), nitrite, uric acid, ketones, lactate, pH, human IgG, total iron, pathogenic bacteria (e.g.. Pseudomonas aeruginosa, Staphylococcus aureus), ABO antigens, alkaline phosphate, Ee(III)... 

Many researchers focus on promoting lab-on-a-chip devices into point-of-care diagnostic products, which feature tiny volume of reagents and samples and portable and on-site detection. However, conventional lab-on-a-chip products are limited by high cost, complex fabrication process, and tedious operation procedures. Therefore, toward a new generation of lab-on-a-chip device, paper microfluidic sensor has been developed, and this novel device has the advantages of rapid fabrication, low cost, and easy to operate, which could have dominant commercial value in the market [8]. 

Zang DJ, Ge L, Van M, Song XR, Yu JH (2012) Electrochemical immunoassay on a 3D microfluidic paper-based device. Chem Common 48(39) 4683-4685... 

Natrajan VK, Christensen KT (2008) A Two-Color Huorescent Thermometry Technique for Microfluidic Devices. AIAA Paper 2008-0689, pp 1-10... 

Paper has been used as a substrate for writing or recording information for 2000 years. Continuation of its use to date is due to the fact that its primary component, cellulose, is a ubiquitous, biodegradable, flexible, renewable, and inexpensive biopolymer. Although paper has been used extensively for printing, writing, and packaging, alternative innovative uses have received much attention within the past 10 years. For instance, processes to fabricate transistors [1,2], batteries and supercapacitors [3,4], sensors [5,6], and microfluidic devices [7-10] on paper substrates have been reported. Unfortimately, the inherently hydrophilic and oleophilic properties of paper limit its ultimate usefulness in many potential applications. 

A.K. Ellerbee, et al.. Quantifying colorimetric assays in paper-based microfluidic devices by measuring the transmission of hght through paper. Analytical Chemistry 81 (20) (2009) 8447-8452. 

Martinez, A.W. et al. 2008. Simple telemedicine for developing regions camera phones and paper-based microfluidic devices for real-time, off-site diagnosis. Anal. Chem. 80, 3699-3707. 

Nie, Z., Deiss, R, Liu, X., Akbulut, O., Whitesides, G.M., 2010. Integration of paper-based microfluidic devices with commercial electrochemical readers. Lab. Chip 10, 3163-3169. http //dx.doi.Org/10.1039/c01c00237b. 

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