Detection, inside chip

Implementation of fluidic functions inside a plate reader is however not a straightforward task. For short-term detection, the chip depicted in Fig. lOf [16] in the Chapter Perfusion Based Cell Culture Chips of this book could be amenable for use with a plate reader since its function does not require any external pump. However, for long- term real-time monitoring, this system is not suitable due to the need for a CO2 incubator. An alternative approach could be based on a multichannel pump, suitable for integration with a polymeric microfluidic cell culture chip independent of a CO2 incubator. The pump shown in Fig. 10b [17] in the Chapter Perfusion Based Cell Culture Chips of this book could function as the basis for such an approach. 

Abstract Optical detection continues to dominate detection methods in microfluidics due to its noninvasive nature, easy coupling, rapid response, and high sensitivity. In this review, we summarize two aspects of recent developments in optical detection methods on microfluidic chips. The first aspect is free-space (off-chip) detection on the microchip, in which the conventional absorption, fluorescence, chemiluminescence, surface plasmon resonance, and surface enhanced Raman spectroscopies are involved. The second aspect is the optofluidic (inside-chip) detection. Various miniaturized optical components integrated on the microfluidic chip, such as waveguide, microlens, laser, and detectors are outlined. 

Sensors of the future will be incredibly small and capable. Many will feature a chemical laboratory and a computer on a chip. They will enable chemical engineers to detect chemical compositions inside hostile process enviromnents and revolutionize their ability to control processes. 

The ability to modulate electrochemical reactivity and effectively switch OFF the reaction was extended further by Wang and coworkers [174] to control, on-demand, the separation and detection processes in microfiuidic devices. In this work, the catalytic nickel nanowires were placed, reoriented and removed on-demand at the exit of the separation channel of the microfiuidic chip, offering unique possibilities for controlling externally, events inside and outside a microchannel. 

We have shown that SERS-encoded particles have been established as a solid and reliable analytical technique for the detection in extremely low amounts of a wide variety of bioanalytes. SERS-encoded particles for indirect detection and labeling can be implemented on chip or even inside living cells, tissues, or a variety of microorganisms. 

Today, Caliper Life Sciences, MA, USA [255] and Agilent Technologies, CA, USA [256] offer microfluidic chips for DNA and Protein analysis. Liquid propulsion is provided via electroosmosis and combined with capillary electrophoretic separation. The sample is electroosmotically transported and metered inside the chip, then separated via capillary electrophoresis and analysed by fluorescence detection. (Fig. 14). The whole assay is performed within minutes, instead of hours or days. 

The development of a cellular microenvironment in a microfluidic chip starts with device fabrication. The most commonly used material for fabrication is polydimethylsiloxane (PDMS). One of the most important components to develop such platforms is the extracellular matrix (ECM), which is the 3D cellular microenvironment. Different approaches have been followed to pattern the ECM inside the microfluidic device, which will significantly affect the arrangement of cells on the chip. Following this, the target cells are seeded and cultured. Such cell culture techniques would be common for drug screening as well as the fundamental research. But for CTCs detection, usually the antibodies will be immobilized on the chip before introducing the cells. 

Using the similar principle of contact imaging, an optofluidic fluorescence microscope was fabricated [6]. Here an array of Fresnel zone plates (FZP) were used to generate focused light spots inside the chip. Similar to the OFM, here the FZP is fabricated in a diagonal fashion so that all the portions of the particle can be captured by the sensor (Fig. 2b). Unlike OFM, apertures are not created over the CMOS sensor, but instead specific filters are coated over the CMOS sensor to assist in the detection of fluorescence (Fig. 2a). The performance of the microscope seemed good when compared to... 

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