Portable microfluidic instruments

Fig. 4 Examples of portable microfluidic instruments, (a) The system integrates fluidics, microseparation chips, lasers, optics, high-voltage power supplies, electronic controls, data algorithms, and a user interface into a hand-portable instrument (Reprinted from [55] with permission of The American Chemistry Society), (b) A miniature LED-induced fluorescence microdevice (Reprinted from [56] with permission of The Royal Society of Chemistry), (c) Hand-held isotachophoresis instrument (dimensions 7.6 x 5.7 x 3.8 cm) (Reprinted from [57] with permission of The Royal Society of Chemistry)...

Renzi et al. demonstrated a hand-held microchip-based analytical instrument for detection of proteins [41]. Recently, a portable microfluidic flow cytometer with simultaneously detection of fluorescence and impedance was reported for cell analysis [42]. This system exploited an LED for excitation and detected fluorescent emission with a solid-state photomultiplier (SSPM). 

Recently, diode array systems have been used in fast transient absorption or chemiluminescence measurements due to their capability of providing extensive real-time spectral data. Enzyme kinetics as part of biochemistry relies on fast spectral multiwavelength acquisition. At low costs, diode array instruments are ideal for portable microfluidic bioanalyzers and emerging large-scale integrated microfluidic technologies. 

FernSndez-la-Villa, A Smchez-Barragan, D Pozo-Ayuso, D.F., and Castafio-Alvarez, M. (2012) Smart portable electrophoresis instrument based on multipurpose microfluidic chips with electrochemical detection. Electrophoresis, 33 (17), 2733-2742. 

This chapter demonstrated that microchip electrophoresis reached maturity and is appropriate for analysis of nitrated explosives. However, to create easy-to-operate field portable instruments for pre-blast explosive analysis would require incorporation of world-to-chip interface, which would be able to continuously sample from the environment. Significant progress towards this goal was made and integrated on-chip devices which allow microfluidic chips to sample from virtually any liquid reservoir were demonstrated [25,31]. 

Some of the platforms can also be considered as multi-application platforms, which is of special interest in the field of research instrumentation. Here, portability is of less importance, and the number of multiple parameters per sample as well as programmability (potentially also during an assay run) gains impact. The microfluidic large scale integration and the droplet based electrowetting and surface acoustic waves platforms are such versatile examples. 

However, the flow cytometers are bulky and expansive, and are available only in large reference laboratories. In addition, the required sample volumes are quite large, usually in the 100 pL range. Many clinical applications require frequent blood tests to monitor patients status and the therapy effectiveness. It is highly desirable to use only small amount of blood samples Ifom patients for each test. Furthermore, it is highly desirable to have affordable and portable flow cytometry instruments for field applications, point-of-care applications and applications in resource-limited locations. To overcome these drawbacks and to meet the increasing needs for versatile cellular analyses, efforts have been made recently to apply microfluidics and lab-on-a-chip technologies to flow cytometric analysis of cells. 

Other sectors have been reached since then by the combined use of microfabrication and MS techniques, such as forensics and homeland safety. For instance, microfabrication techniques are now also used in view of the miniaturization of the mass spectrometer itself and its implementation on a microchip to kill the current paradox of combining tiny devices for sample preparation to bulky and almost room-sized instrumentation. From such ongoing development, one can expect soon the appearance of fully integrated and portable devices for on-site analysis, with both the implementation of the microfluidic-based sample preparation step and the MS analysis on a single device of a few inches in size. 

In order to realize field deployable handheld instrumentation, the miniaturization of highly sensitive optical the detection strategies is required. Miniaturized avalanche photodiodes or photomultiplier tubes are required to integrate with microfluidic devices. This configuration will allow not only parallel detection but also a portable system which can be used in the field. 

The key advantage of the microfluidic RPS is its simplicity without other peripheral complex instruments other than a simple electrical circuit and a microscale- or nanoscale-sized channel. Therefore, it is mostly applicable for portable lab-on-a-chip (LOG) devices to detect biopolymers such as DNA, protein, and blood cells. However, the flow rate of the microfluidic RPS is small, and the sensitivity of the microfluidic RPS is limited by the size of the sensing channel, resulting in poor throughput and sensitivity. 

When analyzing complex samples, like the ones in food industry, a separation method is needed to identify and quantify the components of the sample. Among all the commonly used separation methods, CE and microchip-CE display integration compatibility with ECD systems. In addition, microchip-CE offers short analysis time, high separation efficiency, low cost, and low consumption of sample and reagents, and miniaturization. These techniques are particularly well suited for portable instruments and field applications. The combinations of microfluidics, CE, and ECD methods have led to the development of successful portable systems with applications in environmental analysis, food quality control, and medical testing [55, 56,182-184]. 

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