Droplet microfluidics generates and manipulates discrete droplets through immiscible multiphase flows inside microchannels Due to its remarkable advantages, droplet microfluidics bears significant value in an extremely wide range of area In this review, we provide a comprehensive and in-depth insight into droplet microfluidics, covering fundamental research from microfluidic chip fabrication and droplet generation to the applications of droplets in bio(chemical) analysis and materials generation The purpose of this review is to convey the fundamentals of droplet microfluidics, a critical analysis on its current status and challenges, and opinions on its future development We believe this review will promote communications among biology, chemistry, physics, and materials science

Emerging Droplet Microfluidics

Integrated microfluidic devices

With the increasing requirements for microelectromechanical systems (MEMS) regarding stability, miniaturization and integration, novel materials such as wide band gap semiconductors are attracting more attention. Polycrystalline SiC has first been implemented into Si micromachining techniques, mainly as etch stop and protective layers. However, the outstanding properties of wide band gap semiconductors offer many more possibilities for the implementation of new functionalities. Now, a variety of technologies for SiC and group III nitrides exist to fabricate fully wide band gap semiconductor based MEMS. In this paper we first review the basic technology (deposition and etching) for group III nitrides and SiC with a special focus on the fabrication of three-dimensional microstructures relevant for MEMS. The basic operation principle for MEMS with wide band gap semiconductors is described. Finally, the first applications of SiC based MEMS are demonstrated, and innovative MEMS and NEMS devices are reviewed.

http://iopscience.iop.org/article/10.1088/0022-3727/40/20/S19/pdf

Group III nitride and SiC based MEMS and NEMS: materials properties, technology and applications

This paper describes the main protocols that are used for fabricating microfluidic devices from glass and silicon. Methods for micropatterning glass and silicon are surveyed, and their limitations are discussed. Bonding methods that can be used for joining these materials are summarized and key process parameters are indicated. The paper also outlines techniques for forming electrical connections between microfluidic devices and external circuits. A framework is proposed for the synthesis of a complete glass/silicon device fabrication flow.

/pdf/a-practical-guide-for-the-fabrication-of-microfluidic-24x4pdzxby.pdf

A practical guide for the fabrication of microfluidic devices using glass and silicon

A microfluidic actuator based on thermoresponsive hydrogels

Glass microdevices for capillary electrophoresis (CE) gained a lot of interest in the development of micrototal analysis systems (μTAS). The fabrication of a μJAS requires integration of sampling, chemical separation and detection systems into a microdevice. The integration of a detection system into a microchannel, however, is hampered by the lack of suitable microfabrication technology. Here, a microfabrication method for integration of insulated microelectrodes inside a leakage-free microchannel in glass is presented. A combination of newly developed technological approaches, such as low-temperature glass-to-glass anodic bonding, channel etching, fabrication of buried metal interconnects, and deposition of thin plasma-enhanced chemical vapour deposition (PECVD) silicon carbide layers, enables the fabrication of a CE microdevice with an integrated contactless conductivity detector. The fabrication method of this CE microdevice with integrated contactless conductivity detector is described in detail. Standard CE separations of three inorganic cations in concentrations down to 5 μm show the viability of the new μCE system.

Fabrication of a glass-implemented microcapillary electrophoresis device with integrated contactless conductivity detection.

Influence of Deposition Parameters and Temperature on Stress and Strain of In Situ Doped PECVD Silicon Carbide

We report on the fabrication of molybdenum (Mo) nanopillar (NP) arrays with NP diameters down to 75 nm by means of deep-reactive ion etching at cryogenic temperatures. A variable-thickness Mo metal layer sputtered onto a Si3N4/Si substrate makes possible NPs with different lengths in a controllable manner. We demonstrate how our fabrication strategy leads to tunable cross-sections with different geometries, including hexagonal, cylindrical, square and triangular shapes, by using electron beam lithography on hydrogen silsesquioxane negative tone resist. To ensure well-defined facets and surfaces, we employ deep-reactive ion etching in a gas mixture of SF6 and O2 at cryogenic temperatures in an inductively coupled plasma reactive ion etching (ICP-RIE) system. These results represent an attractive route towards the realization of high-density Mo NP arrays for applications from nanoelectronics to quantum sensing and hydrogen evolution reaction catalysis.

Molybdenum nanopillar arrays: Fabrication and engineering

In this paper, we report on mechanical and structural properties of in-situ n- and p-type PECVD Silicon Carbide (SiC) thin films for post-process surface micromachining The effect of the doping on the film properties is investigated and compared to undoped layers A clear increase in deposition rate is observed when adding the doping gas The effect is more pronounced for p-type doping The etch rate in a reactive ion etcher using fluorine-based chemistry is clearly affected by the doping gas level For p-type films a slight decrease is observed, while for n-type films a sensible increase is measured The stress is in the tensile region and somewhat larger than for undoped films However, while for the phosphorous-doped films this increase is very small and almost insensitive to the doping gas level, for the boron-doped films the effect of doping level is much more pronounced Structural and compositional analysis is preformed to understand the effect of the doping on the mechanical properties of these films

Mechanical and structural properties of in-situ doped PECVD silicon carbide layer for post-processing surface micromachining

High stress levels can cause problems for both electronics and micromechanics. It is therefore important to characterize the stress and strain of the different mechanical layers used for processing. In order to predict the properties of a multilayered structure it is not sufficient to know the mechanical properties of each independent layer. The deposited layers may have a considerable effect on the mechanical properties of the underlying layer. This paper discusses the importance of the effect of each layer on underlying layers and on the total structure, using poly-silicon and silicon- nitride as the mechanical layers. The measurements show that at an anneal of 850 degrees Celsius the influence of nitride on the underlying poly is considerable. At an anneal of 1000 degrees Celsius this effect disappears. We also examined the stress in poly-nitride-poly layers in order to find out the influence of annealing in between the deposition of the layers. Measurements show that the temperature of the anneal is the dominant factor.

Charles R. de Boer

Papers

Fabrication of a glass-implemented microcapillary electrophoresis device with integrated contactless conductivity detection.

Influence of Deposition Parameters and Temperature on Stress and Strain of In Situ Doped PECVD Silicon Carbide

Molybdenum nanopillar arrays: Fabrication and engineering

Mechanical and structural properties of in-situ doped PECVD silicon carbide layer for post-processing surface micromachining

Strain effects in multilayers