Micro fluidic systems

Microfabrication techniques used for the production of MEMS (micro electro-mechanical systems) have been successfully used to produce highly efficient micro fluidic systems. 

Bayraktar T, Pidugu SB (2006) Characterization of liquid flows in micro-fluidic systems. Int J Heat Mass Transfer 49 815-824... 

Wegeng et al. mentioned fouling as a major problem, decreasing micro-fluidic system reliability [1]. Active control over fouling was demanded in their review, but no strategies to overcome it were given. 

Mass transfer of a solute dissolved in a fluid is not only the fundamental mechanism of mixing processes, it also determines the residence-time distribution in micro fluidic systems. As mentioned in Section 1.4, in many applications it is desir-... 

Agilent Technologies Micro Fluidic Systems Naval Medical Research Center SRI... 

Tamanaha C.R., Whitman L.J., Colton R.J., Hybrid macro-micro fluidics system for a chip-based biosensor,./. Micromech. Microeng. 2002 12 N7. 

Yang, L. J., Banada, P. P., Chatni, R., Lim, K. S., Bhunia, A. K., Ladisch, M., and Bashir, R. (2006). A multifunctional micro-fluidic system for dielectrophoretic concentration coupled with immunocapture of low numbers of Listeria monocytogenes. Lab Chip 6, 896-905. 

The structurally programmable micro fluidic system consists of passive valves and flow conduits, which provide different pressure drops. These pressure drops depend on the structure and surface properties of the fluidic paths. The pressure drops can be controlled by tailoring the length of the flow paths and the relative restriction ratio of the passive valves [71]. 

From the Hagen-Poiseuille equation, the pressure drop in a micro fluidic system with laminar flow can be derived (compare [9]) ... 

R 6] In Figure 4.15 a schematic of the programmable micro fluidic system used is shown. All channel pairs are adjusted to have the same volume. At the first split-off point, a passive micro valve, Rl, ensures the fluid filling in the opposite channel system 1 (see upper branch in Figure 4.15) first. The micro valve Rl is designed so that channel 2 can be filled if the pressure exceeds the pressure drop of Rl caused... 

To form a highly resistive interface between the ASIC surface and the fluidic system, a polymer layer of Cyclotene is deposited on the ASIC surface before fabrication of the polymeric micro fluidic system. Cyclotene has high electrical resistance and good chemical stability. The excellent transmission properties ranging... 

Carbon fiber electrodes ( 100 nm dia.) were also used to characterize the diffusion between adjacent stream zones at the interface between a micro fluidic system (16 channels 50 im wide, 57 im deep, separated by a 22- im wall) and a large volume using 10 mM ferrocyanide and amperometric detection [756]. It was reported that when the carbon fiber electrode was used in a PDMS chip, the in-channel format gave better peak symmetry than the end-channel format [757]. 

Lee, E.S., Howard, D., Liang, E.Z., Collins, S.D., Smith, R.L., Removable tubing interconnects for glass-based micro-fluidic systems made using ECDM. J. Micro-mech. Microeng. 2004, 14, 535-541. 

Although monitoring of a flowing sample is inherent to techniques such as mass spectrometry, flame atomic absorption spectrometry and chromatography, even when the instrument is operated manually these techniques are not considered to belong to the field of flow analysis by the analytical community. Therefore, a deeper discussion of these techniques, as well as capillary electrophoresis and micro-fluidic systems, is not undertaken. 

H.J. Kim, A. Beskok, Quantification of chaotic strength and mixing in a micro fluidic system,/. Micromech. Microeng., 17 2197-2210 (2007). 

Figure 10. (A) A micro fluidic system with integrated microelectrode arrays to monitor exocytosis from cultured cells. (Reprinted with permission from Ref [60], 2008 American Chemical Society.)...

Yang Z, Goto H, Matsumoto M, Maeda R (2000) Active micromixer for micro fluidic systems using lead-zirconate-titanate (PZT)-generated ultrasonic vibration. Electrophoresis 21(1) 116-119... 

Bien, D.E., Chiriac, V.A. A novel molecular approach to modeling phase change in micro-fluidic systems. In Proceedings of the 9th Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, pp. 598-604. IEEE, New Jersey (2004)... 

The correct specification of the boundary condition of fluid flow near an interface or solid boundary is essential to obtain the analytical and numerical solution of fluid flow problems. The no-slip boundary condition is successful in describing the class of fluid flow problems. The applicability of slip flow condition and the condition at which no-slip boundary condition is invalid is both of academic interest and of practical interest. The recent developments of small-scale micro fluidic systems have raised the importance in the specification of correct boundary condition. 

This entry discusses applications and extensions of feedback control as applied to micro-fluidic systems. Broadly speaking, feedback... 

There is a community of researchers that focus on control of PDEs (see, e.g., [13]), but they have been motivated by applications in macroscale fluid dynamics and chemical processes, and although their research contains valuable insights and technical results, their methods cannot be directly applied to micro-fluidic systems. 

Armani M, Chaudhary S, Probst R, WalkerS, Shapiro B (2005) Control of micro-fluidic systems two examples, results, and challenges. Int J Robust Nonlinear Control 15 785-803... 

Yang L, BanadaPP, Chatni MR, Lim KS, Bhunia AK, Ladisch M, Bashir R (2006) A multifunctional micro-fluidic system for dielectrophorectic concentration coupled with immuno-capture of low number of Listeria monocytogenes. Lab Chip 6 896-905... 

Jason Reese of Strathclyde University has a simple test problem - can standard continuum equations predict the mass flow rate in a micro-fluidic system in which hehum is flowing along a duct of dimensions (1) 7500 jm X (w) 53ti.m X 1.33pm The answer to this is illustrated in Figure 4.20. 

Figure 11.17 Length scales in micro-fluidic systems (from Daresbury Laboratory data).

In essence, this technique allows for the detection of surface binding interactions in real time without the use of labels. Immunosensors that rely on these principles are commercially available from Biacore AB (formerly Pharmacia Biosensor). These are based on the popular BIACORE 3000, BIACORE 2000 and BIACORE probe instruments in conjunction with disposable sensor chips, which may be purchased with affinity capture chemistries in place (e.g. SA5 Sensor Chips with streptavidin bearing surfaces for capture of biotinylated compounds) [92]. These devices incorporate micro-fluidic systems for delivery of reagents required for analysis and are capable of measuring affinities and kinetics of antibody-antigen interactions in addition to analyte concentrations, which can be determined to the picomolar range [93]. 

The use of decision algorithms and feedback in engineered systems to achieve desired performance. An autopilot is an example of feedback control, it uses decision algorithms and feedback to control the flight of an airplane. In this entry, the engineering systems are micro-fluidic systems. 

This entry discusses applications and extensions of feedback control as applied to micro-fluidic systems. Broadly speaking, feedback control has been developed for electronic systems and mechanical, fluid, and chemical systems on the macro-scale, but not for micro-fluidic systems. 

Fundamental principles for effective control of MEMS, including micro-fluidic systems, have not yet been established. In micro-fluidics, there is a need to control the... 

---