Microsystems advantage

The examples given above as well as those in other chapters of this volume demonstrate the utility of microreaction technology in chemical research and development. However, the development of cost-effective, integrated, easy to operate microchemical systems remains a major challenge to realizing the speed and cost advantages promised by chemical microsystems. 

When successful, however, the full advantage of microsystem design can be utilized, i.e., low power consumption, small volume and weight, low cost, cheap, and reproducible mass production, as well as low vacuum requirements, portability, and even long-term application on battery or even energy harvesting power supply can be envisioned. 

Besides the benefits of scale reduction and trypsin immobilization, microsystem technology has other advantages to offer. For example, Ekstrom et al. [345] described a device that integrated an enzyme microreactor with a sample pretreatment robot and... 

Miniaturized biosensors combined with miniaturized sample pretreatment steps will offer one of the true advantages of biosensors over other analytical and bioanalytical methods portability. These future bioanalytical microsystems will have the size of a calculator, and will be much smaller and lighter than a laptop computer. Thus, research and development are needed not only for the miniaturized biosensor part of these bioanalytical microsystems but also for miniaturized sample pretreatment steps. The concentration of sample volumes (especially for environmental and food samples), the purification and extraction of the analyte from a complex sample are as important as the detection of the analyte itself. Finally, integrated pump systems that are independent from the sample components (such as pH and ionic strength), that require little energy and are stable and rugged are still needed. 

When used mainly as a contacting device, the membrane material leads to considerably improved performance for transfer and/or reaction as compared to a classical packing. This is due to a better management of fluid dynamics and mixing conditions, to increased surface areas and to better controlled driving forces. In fact the membrane represents the assembly of a multitude of microsystems, which act in parallel and can be functionalized. With materials structured at the nanoscale level it would be possible to control phenomena at the molecular level. As compared to dispersed beds of microparticles, porous layers have the main advantage of keeping... 

Fast reactions are usually highly exothermic. Therefore, heat removal is also an important factor in controlling extremely fast reactions. Heat transfer takes place through the surface of the reactor. By taking advantage of the fact that microspaces have a large surface area per unit volume compared with macrospaces, heat transfer occurs very rapidly in microsystems, making precise temperature control possible. 

Finally, a section summarizing the general advantages of microfluidic mixers/ reactors is presented. Although of high interest and importance, an in-depth review of microfluidic mixers in a diversity of microsystems for specific applications is not addressed since it falls out of the scope of this chapter. The reader is therefore directed to a number of excellent recent review articles on the specific subjects [9,19, 29-36]. 

The cross-injector enables analyses with microfabricated systems an order of magnitude faster than capillary-based systems. This advantage is due to the extremely small sample zones that can be injected (<1 nL) with the cross-injector, but the consequence of these minute zones is that the cross-injector is extremely inefficient. Samples are typically pipetted at 1-2 p,L volumes into the drilled reservoirs on a microdevice. Even when considering large injected sample plugs of 1 nL and a low-volume, pipetted sample (1 p.L), the cross-injector is only 0.1% efficient. That is, despite the excellent low-volume fluid-handling promises of microsystems, they still require input volumes... 

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