Microsystems create new opportunities for the spatial and temporal control of cell growth and stimuli by combining surfaces that mimic complex biochemistries and geometries of the extracellular matrix with microfluidic channels that regulate transport of fluids and soluble factors. Further integration with bioanalytic microsystems results in multifunctional platforms for basic biological insights into cells and tissues, as well as for cell-based sensors with biochemical, biomedical and environmental functions. Highly integrated microdevices show great promise for basic biomedical and pharmaceutical research, and robust and portable point-of-care devices could be used in clinical settings, in both the developed and the developing world.

Cells on chips

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

Miniaturization can expand the capability of existing bioassays, separation technologies and chemical synthesis techniques. Although a reduction in size to the micrometre scale will usually not change the nature of molecular reactions, laws of scale for surface per volume, molecular diffusion and heat transport enable dramatic increases in throughput. Besides the many microwell-plate- or bead-based methods, microfluidic chips have been widely used to provide small volumes and fluid connections and could eventually outperform conventionally used robotic fluid handling. Moreover, completely novel applications without a macroscopic equivalent have recently been developed. This article reviews current and future applications of microfluidics and highlights the potential of 'lab-on-a-chip' technology for drug discovery.

Lab-on-a-chip: microfluidics in drug discovery.

Magnetic forces are now being utilised in an amazing variety of microfluidic applications. Magnetohydrodynamic flow has been applied to the pumping of fluids through microchannels. Magnetic materials such as ferrofluids or magnetically doped PDMS have been used as valves. Magnetic microparticles have been employed for mixing of fluid streams. Magnetic particles have also been used as solid supports for bioreactions in microchannels. Trapping and transport of single cells are being investigated and recently, advances have been made towards the detection of magnetic material on-chip. The aim of this review is to introduce and discuss the various developments within the field of magnetism and microfluidics.

Magnetism and microfluidics

We review microfluidic platforms that enable the miniaturization, integration and automation of biochemical assays. Nowadays nearly an unmanageable variety of alternative approaches exists that can do this in principle. Here we focus on those kinds of platforms only that allow performance of a set of microfluidic functions—defined as microfluidic unit operations—which can be easily combined within a well defined and consistent fabrication technology to implement application specific biochemical assays in an easy, flexible and ideally monolithically way. The microfluidic platforms discussed in the following are capillary test strips, also known as lateral flow assays, the “microfluidic large scale integration” approach, centrifugal microfluidics, the electrokinetic platform, pressure driven droplet based microfluidics, electrowetting based microfluidics, SAW driven microfluidics and, last but not least, “free scalable non-contact dispensing”. The microfluidic unit operations discussed within those platforms are fluid transport, metering, mixing, switching, incubation, separation, droplet formation, droplet splitting, nL and pL dispensing, and detection.

/pdf/microfluidic-platforms-for-lab-on-a-chip-applications-2xenxmlmto.pdf

Microfluidic platforms for lab-on-a-chip applications

Micro total analysis systems. Recent developments.

To match the current speed of drug development there is a serious requirement for the pharmaceutical industry to upgrade powder handling processes. Miniaturisation is a key concept especially in the early stages of drug development when only small amounts of the drug compound are available. This paper shows for the first time the application of miniaturisation through chip technology for dry powder handling. Two methods to separate and transport minute amounts of dry powder particles on chip are described. Both techniques could be employed in small scale mixing devices, which depend on reliable particle feeding systems to substitute balances and the time consuming weighing process.

Dry powder injection on chip

A powder injection method and a powder injection microchip, the powder injection microchip comprising: a gas supply inlet (6) for supplying gas; an outlet (8); a channel (4) in fluid connection with the gas supply inlet and the outlet; a powder inlet (12) in fluid connection with the channel, for receiving a first, open end of a powder reservoir (14), the powder reservoir having an opening (22) at or near to a second end of the powder reservoir to allow egress of gas from the powder reservoir at a point distal to the first end of the powder reservoir. The method comprises the steps of: i) supplying gas via the gas supply inlet (6) to the channel (4) and the powder inlet (12) at a velocity sufficient to cause fluidisation of powder at the powder inlet (12); (ii) reducing the supply of gas to cause powder to pass from the powder inlet and to collect in a region of the channel adjacent a point where the powder inlet connects with the channel; and (iii) repeating steps (i) and (ii) as many times as required, subsequent initialisation of step (i) causing the powder collected in the channel to be moved by the gas towards the outlet.

Powder injection system and method

A powder mixing microchip for mixing powder components, a powder mixing system incorporating the same and a powder mixing method for mixing powder components, the powder mixing microchip comprising: a powder mixing unit (1) for mixing a plurality of powder components to provide a powder mixture, the powder mixing unit including a powder mixing (5) channel in which powder components are mixed on being transported there through, a powder outlet port (8) through which the powder mixture is delivered, and a plurality of mixing gas supply channels (7) fluidly connected to the powder mixing channel at spaced locations along a length thereof through which mixing gas flows are delivered to effect mixing of the powder components on being transported through the powder mixing channel.

Torsten Vilkner

Papers

Micro total analysis systems. Recent developments.

Dry powder injection on chip

Powder injection system and method

Powder mixing microchip, system and method

Pulverzufuhrsystem und verfahren