Microfluidics digital

Basic liquid unit volume of a digital microfluidic architecture is fixed by the geometry of the system. The volumetric flow rate is determined by the droplet transport rate and the number of droplets tfansported. The use of unit volume droplet allows the microfluidic functions to be reduced to a set of basic operations. This also facilitates the accomplishment of digitization processes. 

The digital microfluidic system has the following overall benefits  

No moving parts There is no requirement of valves and pumps in the digital microfluidic systems. 

Evaporation Evaporation can be controlled depending on the medium surrounding the droplets. 

No ohmic current Direct current is blocked, leading to minimization of sample heating 

Disadvantages of conventional microchips include resistance to hydrodynamic flow (backpressure), adsorption of some biomolecules on walls, and limited robustness (e.g., clogging narrow channels). Digital microfluidic systems overcome the problems with mixing reagents, which are normally associated with conventional microfluidic devices that use laminar hydrodynamic flow. Such microscale platforms are normally based on the electrowetting-on-dielectric (EWOD) principle [66]. In these digital microchips. 

Universal electronic modules have recently gained huge popularity among analytical chemists because their implementation does not require expert knowledge and investment of funds [77]. Single-board microcontrollers and micro-computers such as Arduino, 

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Fair, R. B., A. Khlystov, V. Srinivasan, V. K. Pamula, and K. N. Weaver. Integrated chemical/biochemical sample collection, pre-concentration, and analysis on a digital microfluidic lab-on-a-chip platform. Proc. SPIE 5591, 113-124 (2004). 

Pair, P., Pamula, V. K., Fair, R. B., Rapid droplet mixers for digital microfluidic systems, Lab Chip 2003, 3, 253-259. 

R.B. Fair, Digital microfluidics is a tine lab-on-a-chip possible Microflttidics and Nanoflttidics, 3, 245-281, (2007). 

SCALING FUNDAMENTALS AND APPLICATIONS OF DIGITAL MICROFLUIDIC MICROSYSTEMS... 

Digital microfluidic architecture is under software-driven electronic control, eliminating the need for mechanical tubes, pumps, and valves that are required for continuous-flow systems. The compatibility of each chemical substance with the electro-wetting platform must be determined initially. Compatibility issues include the following (1) Does the liquid s viscosity and surface tension allow for droplet dispensing and transport by electrowetting ... 

Figure 6. Two-dimensional electrowetting electrode array used in digital microfluidic architecture.

Demonstrations of numerous applications of digital microfluidics have been made in the past five years. Some examples are presented below. 

Investigators working in the field of digital microfluidics have conducted extensive research on the basic principles and operations underlying the implementation of electrowetting-based microfluidic systems. The result is a substantial microfluidic toolkit of automated droplet operations, a sizable... 

H. Moon, A.R. Wheeler, R.L. Garrell, J.A. Loo, and C-J Kim, An integrated digital microfluidic chip for multiplexed proteomic sample preparation and analysis by MADDA-MS. Lab Chip 6, 1213-1219 (2006). 

E.S. Baird and K. Mohseni, A unified velocity model for digital microfluidics. Nanoscale and Microscale Thermophysical Engrg. 11, 109-120 (2007). 

R.-F. Yue, J.-G. Wu, X.F. Zeng, M. Kang, and L.T. Liu, Demonstration of four fundamental operations of liquid droplets for digital microfluidic systems based on an electrowetting-on-dielectric actuator. Chin. Phys. Lett. 23, 2303-2306 (2006). 

V. Srinivasan, V.K. Pamula, M.K. Pollack, and R.B. Fair, Clinical diagnostics on human whole blood, plasma, semm, urine, saliva, sweat, and tears on a digital microfluidic platform. Proceedings ofMicroTAS 2003 1287-1290 (2003). 

S.-K. Cho S.-K. Fan H. Moon H and C.-J. Kim, Towards digital microfluidic circuits creating, transporting, cutting and merging liquid droplets by electrowetting-based actuation, Tech. Dig. MEMS 2002 IEEE Inter Conf on Micro Electro Mechaiucal Systems, 11, 454-61 (2002). 

M.G. Pollack, Electrowetting-based Microactuation of Droplets for Digital Microfluidics. Ph.D. Thesis, Duke Uiuversity (2001). 

A.R. Wheeler, H. Moon, C.A. Bird, R.R. Orgazalek Loo, C-J Kim, J.A. Loo and R.L. Garrell, Digital microfluidics with in-line sample purification for proteomics analyses with MALDI-MS. Anal Chem 77, 534-540 (2005). 

J. Gorbatsova, M. Jaanus and M. Kaljurand, Digital microfluidic sampler for a portable capillary electropherograph, Chem 81, 8590-8595 (2009). 

L. Luan, R.D. Evans, D. Schwiim, R.B. Fair, and N.M. Jokerst, Chip scale integration of optical microresonator sensors with digital microfluidics systems, LEOS-2008, Newport Beach, CA, Nov. 9-13 (2008). 

Y. Wang, Y. Zhao, and K.C. Sung, Efficient in-droplet separation of magnetic particles for digital microfluidics, J. Micromechanics and Microengineering 17, 2148 (2007). 

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