Microfluidics-a review

Gravesen, Peter; Branebjerg, Jens; Jensen, O.S.

doi:10.1088/0960-1317/3/4/002

Cited by 942 publications

(486 citation statements)

References 49 publications

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“…Several other reviews in the literature have analyzed this field by focusing on the development of microfluidic systems, their different designs, microfabrication methods and the individual characteristics of the actuator components that can be incorporated to control flow (Gravesen et al, 1993;Beebe et al, 2002;Oh and Ahn, 2006). However, there is a lack in the literature of a review that analyses the field by focusing on the work that has recently been done in the development of intelligent materials that serve as the fundamental components of non-mechanical actuators.…”

Section: Figurementioning

confidence: 99%

“…In addition, development of a wide variety of techniques in microfabrication has allowed constructing microfluidic systems with sophisticated circuitries at a low cost and by following simple step-series procedures. Simplifying their fabrication permitted exploiting the many fascinating properties present in microfluidic systems, such as the ones shown in Figure 1, which include: 1) their capability to manipulate fluids at microscales; 2) the effective mass and heat transfer that develops due to their high surface to volume ratios; and 3) the dominance of viscous forces within these systems, which facilitate the creation of laminar flows (Gravesen et al, 1993) and allow the generation of diffusive chemical gradients when two substances are transported in parallel within the same channel. (Takayama et al, 2001;Hung et al, 2004;Wu et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Environmentally responsive polymeric "intelligent" materials: the ideal components of non-mechanical valves that control flow in microfluidic systems

Morones‐Ramírez¹

2010

Braz. J. Chem. Eng.

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-Miniaturization and commercialization of integrated microfluidic systems has had great success with the development of a wide variety of techniques in microfabrication, since they allowed their construction at a low cost and by following simple step-series procedures. However, one of the major challenges in the design of microfluidic systems is to achieve control of flow and delivery of different chemical reagents. This feature is especially important when using microfluidic systems in the development of cell culture systems, the construction of labs on a chip and the fabrication and design of chemical microreactors. Spatiotemporal control of the microenvironment in microfluidic devices has been only partially achieved by incorporating actuator parts (mechanical and non-mechanical) within these devices; nevertheless, recently there has been enormous progress due to advances in the materials sciences, and the development of novel polymeric "intelligent" materials. These materials have proved to be excellent candidates in the construction of non-mechanical actuators in the form of environmentally responsive valves. These valves can more efficiently control flows because these "intelligent" materials are capable of undergoing conformational changes and phase transitions in response to different local or external environmental stimuli; allowing them to turn the valves from "on" to "off". In addition, these valves have very simple designs, and are easy and cheap to incorporate into microfluidic systems. Therefore, although there are many reviews that focus on the development and design of non-mechanical actuators, the following review proceeds to describe the exciting characteristics, potential uses and synthesis methods of the building blocks of the most recent and innovative non-mechanical valves, environmentally responsive polymeric "intelligent" materials. In addition, the last section of this review will focus on the synthesis of composite materials that are capable of responding to more than one type of stimulus, since these materials are believed to be the future components that will boost the development of microfluidic systems with spatiotemporal controlled microenvironments.

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Section: Figurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Environmentally responsive polymeric "intelligent" materials: the ideal components of non-mechanical valves that control flow in microfluidic systems

Morones‐Ramírez¹

2010

Braz. J. Chem. Eng.

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“…A commonly used analytical description of flow characteristics in microinjectors allowed us to design our devices. [27][28][29][30] Flow rate Q per applied pressure DP through a microchannel is given by…”

Section: Mems-based Injection Systemmentioning

confidence: 99%

Automated MEMS-based Drosophila embryo injection system for high-throughput RNAi screens

et al. 2006

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We have developed an automated system based on microelectromechanical systems (MEMS) injectors for reliable mass-injection of Drosophila embryos. Targeted applications are high-throughput RNA interference (RNAi) screens. Our injection needles are made of silicon nitride. The liquid to be injected is stored in an integrated 500 nl reservoir, and an externally applied air pressure pulse precisely controls the injected volume. A steady-state water flow rate per applied pressure of 1.2 nl s 21 bar 21 was measured for a needle with channel width, height and length of 6.1 mm, 2.3 mm and 350 mm, respectively. A typical volume of 60 pl per embryo can be reliably and rapidly delivered within tens of milliseconds. Theoretical predictions of flow rates match measured values within ¡10%. Embryos are attached to a glass slide surface and covered with oil. Packages with the injector chip and the embryo slide are mounted on motorized xyz-stages. Two cameras allow the user to quickly align the needle tip to alignment marks on the glass slide. Our system then automatically screens the glass slide for embryos and reliably detects and injects more than 98% of all embryos. Survival rates after deionized (DI) water injection of 80% and higher were achieved. A first RNAi experiment was successfully performed with double-stranded RNA (dsRNA) corresponding to the segment polarity gene armadillo at a concentration of 0.01 mM. Almost 80% of the injected embryos expressed an expected strong loss-of-function phenotype. Our system can replace current manual injection technologies and will support systematic identification of Drosophila gene functions.

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“…1 At Re < 15 in an orifice and Re < 30L/D h for a short channel (where L is the channel length and D h is the hydraulic diameter), fluid transitions into the laminar regime and inertial effects become minimal while viscous forces dominate. 3 Although laminar flow may be advantageous when designing flow control microsystems, it is a cumbersome problem when fast mixing of liquids is desired. Molecular diffusion dominates at these low Reynold's numbers and the diffusion time depends on the channel width.…”

Section: Introductionmentioning

confidence: 99%

A fast passive and planar liquid sample micromixer

et al. 2004

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A novel microdevice for passively mixing liquid samples based on surface tension and a geometrical mixing chamber is presented. Due to the laminar flow regime on the microscale, mixing becomes difficult if not impossible. We present a micromixer where a constantly changing time dependent flow pattern inside a two sample liquid plug is created as the plug simply passes through the planar mixer chamber. The device requires no actuation during mixing and is fabricated using a single etch process. The effective mixing of two coloured liquid samples is demonstrated.

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Microfluidics-a review

Cited by 942 publications

References 49 publications

Environmentally responsive polymeric "intelligent" materials: the ideal components of non-mechanical valves that control flow in microfluidic systems

Environmentally responsive polymeric "intelligent" materials: the ideal components of non-mechanical valves that control flow in microfluidic systems

Automated MEMS-based Drosophila embryo injection system for high-throughput RNAi screens

A fast passive and planar liquid sample micromixer

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