There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Technology 4403 Microfabrication 4403 Assembly and Interfacing 4404 Optical Integration 4405 Flow Control 4405 Standard Operations 4406 Sample Preparation 4406 Injection and Separation 4407 Fluidic Reactors 4407 Particle and Cell Sorting 4409 Cell Trapping and Culture 4409 Applications 4410 Clinical Diagnostics 4410 Nucleic Acids 4411 Proteins 4412 Cell and Tissue Studies 4413 Environmental Monitoring 4414 Literature Cited 4414

Micro total analysis systems: latest achievements.

Dripping and jetting regimes in microfluidic multiphase flows have been investigated extensively, and this review summarizes the main observations and physical understandings in this field to date for three common device geometries: coaxial, flow-focusing and T-junction. The format of the presentation allows for simple and direct comparison of the different conditions for drop and jet formation, as well as the relative ease and utility of forming either drops or jets among the three geometries. The emphasis is on the use of drops and jets as templates for microparticle and microfiber syntheses, and a description is given of the more common methods of solidification and strategies for achieving complex multicomponent microparticles and microfibers.

https://iopscience.iop.org/article/10.1088/0022-3727/46/11/114002/pdf

Dripping and jetting in microfluidic multiphase flows applied to particle and fibre synthesis

This review provides an overview of major microengineering emulsification techniques for production of monodispersed droplets. The main emphasis has been put on membrane emulsification using Shirasu Porous Glass and microsieve membrane, microchannel emulsification using grooved-type and straight-through microchannel plates, microfluidic junctions and flow focusing microfluidic devices. Microfabrication methods for production of planar and 3D poly(dimethylsiloxane) devices, glass capillary microfluidic devices and single-crystal silicon microchannel array devices have been described including soft lithography, glass capillary pulling and microforging, hot embossing, anisotropic wet etching and deep reactive ion etching. In addition, fabrication methods for SPG and microseive membranes have been outlined, such as spinodal decomposition, reactive ion etching and ultraviolet LIGA (Lithography, Electroplating, and Moulding) process. The most widespread application of micromachined emulsification devices is in the synthesis of monodispersed particles and vesicles, such as polymeric particles, microgels, solid lipid particles, Janus particles, and functional vesicles (liposomes, polymersomes and colloidosomes). Glass capillary microfluidic devices are very suitable for production of core/shell drops of controllable shell thickness and multiple emulsions containing a controlled number of inner droplets and/or inner droplets of two or more distinct phases. Microchannel emulsification is a very promising technique for production of monodispersed droplets with droplet throughputs of up to 100 l h−1.

/pdf/production-of-uniform-droplets-using-membrane-microchannel-1i4zkihdxq.pdf

Production of uniform droplets using membrane, microchannel and microfluidic emulsification devices

Industrial lab-on-a-chip: Design, applications and scale-up for drug discovery and delivery

Portable Lab-on-PCB platform for autonomous micromixing

A novel fabrication process called BETTS (bonding, UV exposing and transferring technique in SU-8) is presented in this paper. SU-8 layers can be transferred and patterned over SU-8 microstructures by means of a removable, flexible and transparent substrate. This substrate is composed of a thin acetate film, which can be also used as a mask, and a cured PDMS layer deposited over it. SU-8 is then spin coated and transferred to the SU-8 structures performing simultaneously the steps of bonding and transferring by UV exposure. Due to the low adhesion between PDMS and SU-8, acetate film removal can be easily performed. BETTS provides easy, irreversible and robust SU-8 to SU-8 bonding, where the absence of oxygen plasma equipment or vacuum systems decreases drastically the fabrication cost and time involved. The reported fabrication process makes it possible to fabricate complex SU-8 three-dimensional structures using a simple and inexpensive procedure and also ensures its compatibility and integration with microfluidic and PCB-MEMS devices. Some specific applications such as multilevel microchannel network, patterned membranes, microchambers and microvalves are reported to demonstrate the potential of the proposed process.

https://iopscience.iop.org/article/10.1088/0960-1317/20/3/035008/pdf

BETTS: bonding, exposing and transferring technique in SU-8 for microsystems fabrication

It is well known that the classical laws of circuits have equivalents in fluid movement if certain conditions are met. Usually, equivalence with linear circuits requires laminar flow, which is a typical condition in a microelectromechanical system (MEMS). However, fluidic devices, which are nonlinear in nature, can also have an electronic counterpart, and the tools and procedures used in electronic design can be applied to microfluidic systems. A complete description of the electronic?fluidic correspondence, focused especially on MEMS, can increase the number of ways to design microfluidic networks and open new ways of operating them. The modeling of complex microfluidic networks, in particular, applications, demonstrate the usefulness of the analogy.

Correspondence Between Electronics and Fluids in MEMS: Designing Microfluidic Systems Using Electronics

In this paper, a single-use and unidirectional microvalve with low consumption of energy for PCB-based microfluidic platforms is reported. Its activation is easy because it works as a fuse. The fabrication process of the device is based on PCB technology and a typical SU-8 process, using the PCB as a substrate and SU-8 for the microfluidic channels and chambers. The microvalve is intended to be used to impulse small volumes of fluids and it has been designed to be highly integrable in PCB-based microfluidic platforms. The proposed device has been fabricated, integrated and tested in a general purpose microfluidic circuit, resulting in a low activation time, of about 100 μs, and a low consumption of energy, with a maximum of 27 mJ. These results show a significant improvement because the energy consumption is about 84% lower and the time response is about four orders of magnitude shorter if compared with similar microvalves for impulsion of fluids on PCB-based platforms.

https://iopscience.iop.org/article/10.1088/0960-1317/24/6/065013/pdf

Low consumption single-use microvalve for microfluidic PCB-based platforms

This paper presents a device that is intended to produce emulsions of liquids at a micrometer scale by using the fluidic technique that is known as "flow focusing." This technique consists in the encapsulation of an inner stream by an outer liquid. By controlling both liquid flow rates, extremely thin jets can be produced, with very good control of its thickness and of the produced droplets in the emulsion. The device that is proposed in this paper performs 3D focusing, and in contrast to previously known designs, it is integrable into bidimensional arrays, increasing the overall achievable efficiency. This paper describes the physical principle of flow focusing, presents the fabrication process of the device in silicon using standard microfabrication processes, and shows numerical simulations and experimental results, in good agreement with previously published theoretical behavior.

Francisco Perdigones

Papers

Portable Lab-on-PCB platform for autonomous micromixing

BETTS: bonding, exposing and transferring technique in SU-8 for microsystems fabrication

Correspondence Between Electronics and Fluids in MEMS: Designing Microfluidic Systems Using Electronics

Low consumption single-use microvalve for microfluidic PCB-based platforms

Silicon Microdevice for Emulsion Production Using Three-Dimensional Flow Focusing