Other Chip-based Devices

Electrochemical detection offers also great promise for CZE microchips, and for other chip-based analytical microsystems (e.g., Lab-on-a-Chip) discussed in Section 6.3 (77-83). Particularly attractive for such microfluidic devices are the high sensitivity of electrochemical detection, its inherent miniaturization of both the detector and control instrumentation, low cost, low power demands, and compatibility with micromachining technologies. Various detector configurations, based on different capillary/working-electrode... 

At the millimetre scale, gravity, friction, combustion and electrostatic forces predominate. At the micrometer scale, it is mainly electrostatic forces, van der Waals forces and Brownian motion that are at work. Forces related to volume, like weight and inertia, tend to decrease in significance while forces related to surface area, such as friction and electrostatics, tend to increase in significance. Surface tension, which depends upon an edge, and viscosity both become very significant and impact hugely on the movement of liquids as discussed in the previous section. Hence, sometimes these processes can aid the development of chip-based devices while in other cases they present limitations. 

There are many other types of chip-based devices in development and, indeed, on the market. Many of these are for purpose point-of-care diagnostics. A few of the main categories of chips are discussed here. 

Various PDMS-based tunable optofluidic devices have been developed in the past few years for different applications. In these devices, such pressure tuning methods have many advantages, such as high precision, fast response, compact size, simple fabrication, easy control, and being compatible with other PDMS microfluidic devices in terms of both fabrication and operation. Moreover, multiple such tunable optofluidic elements can be integrated into a single chip, while each of them can be independently controlled. 

Optofluidics holds the most potential in lab-on-a-chip application. Being compatible with conventional microfluidics is the key advantage of elastomer-based tunable optofluidic devices. PDMS microfluidic chips are extensively utilized in biological and chemical studies. Due to similarities in materials and fabrication methods, PDMS-based tunable optofluidic devices can be easily integrated with other PDMS-based microfluidic devices to enable more complex and multiplexed functions. For example, tunable dye laser sources can be used... 

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