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

Nanotechnology is the science of understanding matter and the control of matter at dimensions of 100 nm or less. Encompassing nanoscale science, engineering, and technology, nanotechnology involves imaging, measuring, modeling, and manipulation of matter at this level of precision. An important aspect of research in nanotechnology involves precision control and manipulation of devices and materials at a nanoscale, i.e., nanopositioning. Nanopositioners are precision mechatronic systems designed to move objects over a small range with a resolution down to a fraction of an atomic diameter. The desired attributes of a nanopositioner are extremely high resolution, accuracy, stability, and fast response. The key to successful nanopositioning is accurate position sensing and feedback control of the motion. This paper presents an overview of nanopositioning technologies and devices emphasizing the key role of advanced control techniques in improving precision, accuracy, and speed of operation of these systems.

/pdf/a-survey-of-control-issues-in-nanopositioning-1zgjre9s1l.pdf

A Survey of Control Issues in Nanopositioning

This article reviews acoustic microfiuidics: the use of acoustic fields, principally ultrasonics, for application in microfiuidics. Although acoustics is a classical field, its promising, and indeed perplexing, capabilities in powerfully manipulating both fluids and particles within those fluids on the microscale to nanoscale has revived interest in it. The bewildering state of the literature and ample jargon from decades of research is reorganized and presented in the context of models derived from first principles. This hopefully will make the area accessible for researchers with experience in materials science, fluid mechanics, or dynamics. The abundance of interesting phenomena arising from nonlinear interactions in ultrasound that easily appear at these small scales is considered, especially in surface acoustic wave devices that are simple to fabricate with planar lithography techniques common in microfluidics, along with the many applications in microfluidics and nanofluidics that appear through the literature.

/pdf/microscale-acoustofluidics-microfluidics-driven-via-5bet39j13p.pdf

Microscale acoustofluidics: Microfluidics driven via acoustics and ultrasonics

The aim of microfluidic mixing is to achieve a thorough and rapid mixing of multiple samples in microscale devices. In such devices, sample mixing is essentially achieved by enhancing the diffusion effect between the different species flows. Broadly speaking, microfluidic mixing schemes can be categorized as either “active”, where an external energy force is applied to perturb the sample species, or “passive”, where the contact area and contact time of the species samples are increased through specially-designed microchannel configurations. Many mixers have been proposed to facilitate this task over the past 10 years. Accordingly, this paper commences by providing a high level overview of the field of microfluidic mixing devices before describing some of the more significant proposals for active and passive mixers.

/pdf/microfluidic-mixing-a-review-3egj61w5ox.pdf

Microfluidic Mixing: A Review

The ability to tailor the chemical composition and structure of a surface at the sub-100-nm length scale is important for studying topics ranging from molecular electronics to materials assembly, and for investigating biological recognition at the single biomolecule level. Dip-pen nanolithography (DPN) is a scanning probe microscopy-based nanofabrication technique that uniquely combines direct-write soft-matter compatibility with the high resolution and registry of atomic force microscopy (AFM), which makes it a powerful tool for depositing soft and hard materials, in the form of stable and functional architectures, on a variety of surfaces. The technology is accessible to any researcher who can operate an AFM instrument and is now used by more than 200 laboratories throughout the world. This article introduces DPN and reviews the rapid growth of the field of DPN-enabled research and applications over the past several years.

Applications of dip-pen nanolithography.

We present a technique in which atomic force microscopy at ultrasonic frequencies is used to determine the thickness of thin films. In this technique, the resonance frequency of a flexural mode of an atomic force microscope cantilever is used to determine the tip-sample contact stiffness. This allows the film thickness to be determined, provided that the tip and sample elastic moduli and radii of curvature are known. We report experimental results for thin metal and polymer films deposited on silicon substrates and compare them with the predictions of a theoretical model.

Thin film characterization by atomic force microscopy at ultrasonic frequencies

A system and method describes an inertial sensor assembly, the assembly comprises a substrate parallel to the plane, at least one in-plane angular velocity sensor comprising a pair proof masses that are oscillated in anti-phase fashion along an axis normal to the plane. The first in-plane angular velocity sensor further includes a sensing frame responsive to the angular velocity of the substrate around the first axis parallel to the plane and perpendicular to the axis normal to the plane. The assembly also includes at least one out-of-plane angular velocity sensor comprising a pair of proof masses that are oscillated in anti-phase fashion in the plane parallel to the plane. The out-of-plane angular velocity sensor further comprises a sensing frame responsive to the angular velocity of the substrate around the axis normal to the plane.

Integrated multiaxis motion sensor

Sensors for measuring angular acceleration about three mutually orthogonal axes, X, Y, Z or about the combination of these axes are disclosed The sensor comprises a sensor subassembly The sensor subassembly further comprises a base which is substantially parallel to the X-Y sensing plane; a proof mass disposed in the X-Y sensing plane and constrained to rotate substantially about the X, and/or Y, and/or Z, by at least one linkage and is responsive to angular accelerations about the X, and/or Y, and/or Z directions Finally, the sensor includes at least one electrode at the base plate or perpendicular to the base plate and at least one transducer for each sensing direction of the sensor subassembly responsive to the angular acceleration Multi-axis detection is enabled by adjusting a configuration of flexures and electrodes

Vertically integrated 3-axis mems angular accelerometer with integrated electronics

A system and method for providing a MEMS device with integrated electronics are disclosed. The MEMS device comprises an integrated circuit substrate and a MEMS subassembly coupled to the integrated circuit substrate. The integrated circuit substrate includes at least one circuit coupled to at least one fixed electrode. The MEMS subassembly includes at least one standoff formed by a lithographic process, a flexible plate with a top surface and a bottom surface, and a MEMS electrode coupled to the flexible plate and electrically coupled to the at least one standoff. A force acting on the flexible plate causes a change in a gap between the MEMS electrode and the at least one fixed electrode.

Hermetically sealed mems device with a portion exposed to the environment with vertically integrated electronics

In this work a new technology for designing and manufacturing ultrasonic interdigital transducers (IDT) is presented. The piezoelectric material used is a metallised piezopolymer film made of polyvinylidene fluoride (PVDF) with electrode pattern obtained with a laser ablation process. Piezopolymer transducer prototypes are designed with wavelength of 8 mm to operate with Lamb waves (symmetrical S0 mode). An experimental validation of the piezopolymer IDT design is demonstrated with a transmitter-receiver IDT pair embedded in a 3 mm thick carbon fiber reinforced plastic (CFRP) composite laminate. Acoustical response and the electrical impedance have been calculated. These transducers are proposed for monitoring structural integrity of structures/components made of carbon epoxy composite laminates commonly used in spacecrafts, satellite and airplanes. © 2005 Elsevier B.V. All rights reserved.

Goksen G. Yaralioglu

Papers

Thin film characterization by atomic force microscopy at ultrasonic frequencies

Integrated multiaxis motion sensor

Vertically integrated 3-axis mems angular accelerometer with integrated electronics

Hermetically sealed mems device with a portion exposed to the environment with vertically integrated electronics

A new design and manufacturing process for embedded Lamb waves interdigital transducers based on piezopolymer film