Microfabricated integrated circuits revolutionized computation by vastly reducing the space, labor, and time required for calculations. Microfluidic systems hold similar promise for the large-scale automation of chemistry and biology, suggesting the possibility of numerous experiments performed rapidly and in parallel, while consuming little reagent. While it is too early to tell whether such a vision will be realized, significant progress has been achieved, and various applications of significant scientific and practical interest have been developed. Here a review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena. Specifically, this review explores the Reynolds number Re, addressing inertial effects; the Peclet number Pe, which concerns convective and diffusive transport; the capillary number Ca expressing the importance of interfacial tension; the Deborah, Weissenberg, and elasticity numbers De, Wi, and El, describing elastic effects due to deformable microstructural elements like polymers; the Grashof and Rayleigh numbers Gr and Ra, describing density-driven flows; and the Knudsen number, describing the importance of noncontinuum molecular effects. Furthermore, the long-range nature of viscous flows and the small device dimensions inherent in microfluidics mean that the influence of boundaries is typically significant. A variety of strategies have been developed to manipulate fluids by exploiting boundary effects; among these are electrokinetic effects, acoustic streaming, and fluid-structure interactions. The goal is to describe the physics behind the rich variety of fluid phenomena occurring on the nanoliter scale using simple scaling arguments, with the hopes of developing an intuitive sense for this occasionally counterintuitive world.

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Microfluidics: Fluid physics at the nanoliter scale

We survey progress over the past 25 years in the development of microscale devices for pumping fluids. We attempt to provide both a reference for micropump researchers and a resource for those outside the field who wish to identify the best micropump for a particular application. Reciprocating displacement micropumps have been the subject of extensive research in both academia and the private sector and have been produced with a wide range of actuators, valve configurations and materials. Aperiodic displacement micropumps based on mechanisms such as localized phase change have been shown to be suitable for specialized applications. Electroosmotic micropumps exhibit favorable scaling and are promising for a variety of applications requiring high flow rates and pressures. Dynamic micropumps based on electrohydrodynamic and magnetohydrodynamic effects have also been developed. Much progress has been made, but with micropumps suitable for important applications still not available, this remains a fertile area for future research.

https://microfluidics.stanford.edu/Publications/Micropumps_Cooling/Laser%20Review%20of%20Micropumps%20in%20JMM.pdf

A review of micropumps

This review reports the progress on the recent development of micromixers. The review first presents the different micromixer types and designs. Micromixers in this review are categorized as passive micromixers and active micromixers. Due to the simple fabrication technology and the easy implementation in a complex microfluidic system, passive micromixers will be the focus of this review. Next, the review discusses the operation points of the micromixers based on characteristic dimensionless numbers such as Reynolds number Re, Peclet number Pe, and in dynamic cases the Strouhal number St. The fabrication technologies for different mixer types are also analysed. Quantification techniques for evaluation of the performance of micromixers are discussed. Finally, the review addresses typical applications of micromixers.

https://iopscience.iop.org/article/10.1088/0960-1317/15/2/R01/pdf

Micromixers?a review

Micropumping has emerged as a critical research area for many electronics and biological applications. A significant driving force underlying this research has been the integration of pumping mechanisms in micro total analysis systems and other multi-functional analysis techniques. Uses in electronics packaging and micromixing and microdosing systems have also capitalized on novel pumping concepts. The present work builds upon a number of existing reviews of micropumping strategies by focusing on the large body of micropump advances reported in the very recent literature. Critical selection criteria are included for pumps and valves to aid in determining the pumping mechanism that is most appropriate for a given application. Important limitations or incompatibilities are also addressed. Quantitative comparisons are provided in graphical and tabular forms.

/pdf/recent-advances-in-microscale-pumping-technologies-a-review-4fhnsjk6g9.pdf

Recent advances in microscale pumping technologies: a review and evaluation

https://www.repository.cam.ac.uk/bitstream/1810/264501/1/Fu_et_al-2017-Progress_in_Material_Science-VoR.pdf

Advances in piezoelectric thin films for acoustic biosensors, acoustofluidics and lab-on-chip applications

Microfluidics has emerged from the MEMS-technology as an important research field and a promising market. We give an overview on one of the most important microfluidic components: the micropump. In the last decade, various micropumps have been developed. There are only a few review papers on microfluidic devices and none of them were dedicated only to micropumps. This review paper outlines systematically the pump principles and their realization with MEMS-technology. Comparisons regarding pump size, flow rate, and backpressure will help readers to decide their proper design before starting a microfluidics project. Different pump principles are compared graphically and discussed in terms of their advantages and disadvantages for particular applications

MEMS-Micropumps: A Review

In this paper, a liquid cooling solution has been reported for 3-D package in package-on-package format. A high heat dissipating chip is mounted on a silicon carrier, which has copper through-silicon via (TSV) for electrical interconnection and hollow TSV for fluidic circulation. Heat transfer enhancement structures have been embedded in the chip carrier. Cooling liquid, de-ionized water is circulated through the chip carrier and heat from the chip is extracted. The fluidic channels are isolated from electrical traces using hermetic sealing. The research work has demonstrated liquid cooling solution for 100 W from one stack and total of 200 W from two stacks of the package. The fluidic interconnections and sealing techniques have been discussed.

3-D Packaging With Through-Silicon Via (TSV) for Electrical and Fluidic Interconnections

In this paper a liquid cooling solution has been reported for 3-D package in PoP format. The high heat dissipating chip is mounted on a silicon carrier, which has copper through-silicon via for electrical interconnection and through-silicon hollow via for fluidic circulation. Heat enhancement structures have been embedded in the chip carrier. Cooling liquid, de-ionized water is circulated through the chip carrier and heat from the chip is extracted. The fluidic channels are isolated from electrical traces using hermetic sealing. The research work has demonstrated 100 W of heat dissipation from one stack and total of 200 W from two stacks of the package. The fluidic interconnections and sealing techniques have been discussed.

Toh Kok Chuan

Papers

MEMS-Micropumps: A Review

3-D Packaging With Through-Silicon Via (TSV) for Electrical and Fluidic Interconnections

3D packaging with through ilicon via (TSV) for electrical and fluidic interconnections

Thermal resistance of two solids in contact through a cylindrical joint