■ Abstract Fluid flow at the microscale exhibits unique phenomena that can be leveraged to fabricate devices and components capable of performing functions useful for biological studies. The physics of importance to microfluidics are reviewed. Common methods of fabricating microfluidic devices and systems are described. Components, including valves, mixers, and pumps, capable of controlling fluid flow by utilizing the physics of the microscale are presented. Techniques for sensing flow characteristics are described and examples of devices and systems that perform bioanalysis are presented. The focus of this review is microscale phenomena and the use of the physics of the scale to create devices and systems that provide functionality useful to the life sciences.

https://www.researchgate.net/profile/Glennys_Mensing/publication/11260597_Physics_and_applications_of_microfluidics_in_biology/links/5437f5160cf2027cbb206767.pdf

Physics and applications of microfluidics in biology.

After having reviewed some aspects of microfluidic system preparation in the first part (1), in this second part of the review we will cover a number of standard operations (namely: sample preparation, sample injection, sample manipulation, reaction, separation, and detection) as well as some biological applications of micro total analysis systems (namely: cell culture, polymerase chain reaction, DNA separation, DNA sequencing, and clinical diagnostics). As previously, we will include papers issued from different scientific journals as well as useful abstracts from three conference proceedings: MEMS, Transducers, and μTAS. In this second part, we do not include the period covered by the history section (1975-1997) from part 1 but try to cover the relevant examples of the literature published between January 1998 and March 2002. We briefly describe articles that struck us as needing special attention, while more “standard” papers are dutifully reported in groups of interest. An article might be included in more than one section, depending on the ideas developed in it.

Micro total analysis systems. 2. Analytical standard operations and applications.

Polydimethylsiloxane (PDMS) elastomers are extensively used for soft lithographic replication of microstructures in microfluidic and micro-engineering applications. Elastomeric microstructures are commonly required to fulfil an explicit mechanical role and accordingly their mechanical properties can critically affect device performance. The mechanical properties of elastomers are known to vary with both curing and operational temperatures. However, even for the elastomer most commonly employed in microfluidic applications, Sylgard 184, only a very limited range of data exists regarding the variation in mechanical properties of bulk PDMS with curing temperature. We report an investigation of the variation in the mechanical properties of bulk Sylgard 184 with curing temperature, over the range 25 ◦ C to 200 ◦ C. PDMS samples for tensile and compressive testing were fabricated according to ASTM standards. Data obtained indicates variation in mechanical properties due to curing temperature for Young’s modulus of 1.32‐2.97 MPa, ultimate tensile strength of 3.51‐7.65 MPa, compressive modulus of 117.8‐186.9 MPa and ultimate compressive strength of 28.4‐51.7 GPa in a range up to 40% strain and hardness of 44‐54 ShA.

/pdf/mechanical-characterization-of-bulk-sylgard-184-for-2mkxi71f19.pdf

Mechanical characterization of bulk Sylgard 184 for microfluidics and microengineering

A review of microfluidic devices for cellomics is presented. After a brief description of the historical background of Lab-on-Chip (LOC) devices, different areas are reviewed. Devices for cell sampling are presented, followed by cell trapping and cell sorting devices based upon mechanical and electrical principles. Subsequently, a popular type of cell sorters, flow cytometers, is considered, followed by a chapter describing devices for cell treatment: cell lysis, poration/gene transfection and cell fusion devices. Finally a number of microfluidic devices for cellular studies are reviewed. The large amount of very recent publications treated in this review indicates the rapidly growing interest in this exciting application area of LOC.

/pdf/microfluidic-devices-for-cellomics-a-review-1hng9wltnz.pdf

Microfluidic devices for cellomics: a review

Wearable sensors have recently seen a large increase in both research and commercialization. However, success in wearable sensors has been a mix of both progress and setbacks. Most of commercial progress has been in smart adaptation of existing mechanical, electrical and optical methods of measuring the body. This adaptation has involved innovations in how to miniaturize sensing technologies, how to make them conformal and flexible, and in the development of companion software that increases the value of the measured data. However, chemical sensing modalities have experienced greater challenges in commercial adoption, especially for non-invasive chemical sensors. There have also been significant challenges in making significant fundamental improvements to existing mechanical, electrical, and optical sensing modalities, especially in improving their specificity of detection. Many of these challenges can be understood by appreciating the body's surface (skin) as more of an information barrier than as an information source. With a deeper understanding of the fundamental challenges faced for wearable sensors and of the state-of-the-art for wearable sensor technology, the roadmap becomes clearer for creating the next generation of innovations and breakthroughs.

/pdf/wearable-sensors-modalities-challenges-and-prospects-2tjpw1t9kz.pdf

Wearable sensors: modalities, challenges, and prospects

A microparticle which is invisible to the naked eye and is marked with a machine readable code. A tagging compound comprising a powder, fluid or gas when mixed with one or more set or sets of microparticles of which each has a predetermined shape representative of a unique code selected from a multiplicity of such codes, such that the presence of the microparticles is undetectable to the naked eye.

Coded items for labelling objects

A solid support particle (3) adapted for use in Combinatorial Chemistry Techniques characterised in that the particle (3) is marked with machine readable code (4, 5, 6, 7, 8).

Coded particles for process sequence tracking in combinatorial compound library preparation

A solid support particle (preferably of silicon, silicon dioxide or a metal), adapted for use in Combinatorial Chemistry Techniques, is marked with a machine-readable code. The particle may comprise a first phase, on which the synthesis is performed, and a second phase having the machine-readable code. Preferred particles comprise (i) a bi-layer structure, in which the first and second phases are surperimposed one on another; (ii) encapsulating the second phase, incorporating the code, within the first phase, thus permitting the whole outer surface to be used as a chemical support; or (iii) mechanically linking the two phases, either wherein the second phase is in the form of a wafer, incorporating an aperture, and the first phase extends through said aperture, such that a portion thereof exists on each side of the aperture; or wherein the second phase incorporates at least one barbed, or hook-like, protrusion, adapted to engage the surface of the first phase. The first phase may be selected from porous silicates (especially controlled-pore glass) and polymer resins (especially polystyrene, polyesters, polyacrylamides, poly(meth)acrylates and derivatives thereof). The machine-readable code may be a binary code and/or consist of at least one of the features selected from pits, holes, hollows, grooves or notches, or the code may reside in either the shape of the particle, including that of the second phase, if present. The code may be read optically and further incorporate an orientation marker. A set of support particles, in which each particle of the set is marked with a unique code, is described. The particles may be used to synthesize combinatorial chemical compound libraries, including polypeptides, carbohydrates and other oligomeric compounds, or to characterise and deconvolute members of such a library.

Solid support particle marked with a machine-readable code for use in Combinatorial Chemistry Techniques

An application of silicon micromachining to the analysis of blood cell rheology is described. The system, based upon a micromachined flow cell, provides a specific measurement of each cell in a statistically significant population in terms of both flow velocity profile and an index of cell volume while the cells flow through an array of microchannels. The rationale, design, and fabrication of the silicon micromachined flow cell is discussed. Interrelated considerations determining the design of the associated fluidic, mechanical, imaging, and real-time image analysis subsystems are examined. Sample data comparing normal and iron deficiency anaemic blood are presented to illustrate the potential of this technique. >

M.C. Tracey

Papers

Mechanical characterization of bulk Sylgard 184 for microfluidics and microengineering

Coded items for labelling objects

Coded particles for process sequence tracking in combinatorial compound library preparation

Solid support particle marked with a machine-readable code for use in Combinatorial Chemistry Techniques

A silicon micromachined device for use in blood cell deformability studies