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Micromachines, Volume 4, Issue 4 (December 2013) – 6 articles , Pages 357-443

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Open AccessArticle

A Bi-Directional Out-of-Plane Actuator by Electrostatic Force

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Micromachines 2013, 4(4), 431-443; https://doi.org/10.3390/mi4040431 - 05 Dec 2013

Cited by 6 | Viewed by 7069

Abstract

Presented in this paper is a bi-directional out-of-plane actuator which combines the merits of the electrostatic repulsive principle and the electrostatic attractive principle. By taking advantage of the electrostatic repulsive mode, the common “pull-in” instability can be lessened to enlarge the displacement, and by applying the electrostatic attractive mode, the out-of-plane displacement is further enlarged. The implications of changing the actuator’s physical dimensions are discussed, along with the two-layer polysilicon surface microfabrication process used to fabricate such an actuator. The static characteristics of the out-of-plane displacement versus the voltage of both modes are tested, and displacements of 1.4 μm and 0.63 μm are obtained at 130 V and 15 V, respectively. Therefore, a total stroke of 2.03 μm is achieved, more than 3 fold that of the electrostatic attractive mode, making this actuator useful in optical Micro-Electro-Mechanical Systems (MEMS) and Radio Frequency (RF) MEMS applications. Full article

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Open AccessArticle

Hydrodynamic Cell Trapping for High Throughput Single-Cell Applications

Amin Abbaszadeh Banaeiyan

Doryaneh Ahmadpour

Caroline Beck Adiels

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Mattias Goksör

Micromachines 2013, 4(4), 414-430; https://doi.org/10.3390/mi4040414 - 03 Dec 2013

Cited by 20 | Viewed by 9441

Abstract

The possibility to conduct complete cell assays under a precisely controlled environment while consuming minor amounts of chemicals and precious drugs have made microfluidics an interesting candidate for quantitative single-cell studies. Here, we present an application-specific microfluidic device, cellcomb, capable of conducting high-throughput single-cell experiments. The system employs pure hydrodynamic forces for easy cell trapping and is readily fabricated in polydimethylsiloxane (PDMS) using soft lithography techniques. The cell-trapping array consists of V-shaped pockets designed to accommodate up to six Saccharomyces cerevisiae (yeast cells) with the average diameter of 4 μm. We used this platform to monitor the impact of flow rate modulation on the arsenite (As(III)) uptake in yeast. Redistribution of a green fluorescent protein (GFP)-tagged version of the heat shock protein Hsp104 was followed over time as read out. Results showed a clear reverse correlation between the arsenite uptake and three different adjusted low = 25 nL min⁻¹, moderate = 50 nL min⁻¹, and high = 100 nL min⁻¹ flow rates. We consider the presented device as the first building block of a future integrated application-specific cell-trapping array that can be used to conduct complete single cell experiments on different cell types. Full article

(This article belongs to the Special Issue Micro/Nanofluidic Devices for Single Cell Analysis)

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Open AccessCommunication

Monodisperse Water-in-Oil-in-Water (W/O/W) Double Emulsion Droplets as Uniform Compartments for High-Throughput Analysis via Flow Cytometry

Jing Yan

Wolfgang-Andreas C. Bauer

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Micromachines 2013, 4(4), 402-413; https://doi.org/10.3390/mi4040402 - 03 Dec 2013

Cited by 39 | Viewed by 14113

Abstract

Here we report the application of monodisperse double emulsion droplets, produced in a single step within partially hydrophilic/partially hydrophobic microfluidic devices, as defined containers for quantitative flow cytometric analysis. Samples with varying fluorophore concentrations were generated, and a clear correlation between dye concentration [...] Read more.

(This article belongs to the Collection Lab-on-a-Chip)

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Open AccessArticle

Guard Cell and Tropomyosin Inspired Chemical Sensor

Jacquelyn K.S. Nagel

Micromachines 2013, 4(4), 378-401; https://doi.org/10.3390/mi4040378 - 18 Oct 2013

Cited by 3 | Viewed by 8358

Abstract

Sensors are an integral part of many engineered products and systems. Biological inspiration has the potential to improve current sensor designs as well as inspire innovative ones. This paper presents the design of an innovative, biologically-inspired chemical sensor that performs “up-front” processing through mechanical means. Inspiration from the physiology (function) of the guard cell coupled with the morphology (form) and physiology of tropomyosin resulted in two concept variants for the chemical sensor. Applications of the sensor design include environmental monitoring of harmful gases, and a non-invasive approach to detect illnesses including diabetes, liver disease, and cancer on the breath. Full article

(This article belongs to the Special Issue Bioinspired Microsensors and Micromachines)

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Open AccessArticle

Resistless Fabrication of Nanoimprint Lithography (NIL) Stamps Using Nano-Stencil Lithography

Luis Guillermo Villanueva

Oscar Vazquez-Mena

Cristina Martin-Olmos

Veronica Savu

Katrin Sidler

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Juergen Brugger

Micromachines 2013, 4(4), 370-377; https://doi.org/10.3390/mi4040370 - 15 Oct 2013

Cited by 9 | Viewed by 11712

Abstract

In order to keep up with the advances in nano-fabrication, alternative, cost-efficient lithography techniques need to be implemented. Two of the most promising are nanoimprint lithography (NIL) and stencil lithography. We explore here the possibility of fabricating the stamp using stencil lithography, which has the potential for a cost reduction in some fabrication facilities. We show that the stamps reproduce the membrane aperture patterns within ±10 nm and we validate such stamps by using them to fabricate metallic nanowires down to 100 nm in size. Full article

(This article belongs to the Special Issue Micromachined Tools for Nanoscale Science and Technology)

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Open AccessArticle

Polydimethylsiloxane (PDMS) Sub-Micron Traps for Single-Cell Analysis of Bacteria

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Micromachines 2013, 4(4), 357-369; https://doi.org/10.3390/mi4040357 - 11 Oct 2013

Cited by 40 | Viewed by 10026

Abstract

Microfluidics has become an essential tool in single-cell analysis assays for gaining more accurate insights into cell behavior. Various microfluidics methods have been introduced facilitating single-cell analysis of a broad range of cell types. However, the study of prokaryotic cells such as Escherichia coli and others still faces the challenge of achieving proper single-cell immobilization simply due to their small size and often fast growth rates. Recently, new approaches were presented to investigate bacteria growing in monolayers and single-cell tracks under environmental control. This allows for high-resolution time-lapse observation of cell proliferation, cell morphology and fluorescence-coupled bioreporters. Inside microcolonies, interactions between nearby cells are likely and may cause interference during perturbation studies. In this paper, we present a microfluidic device containing hundred sub-micron sized trapping barrier structures for single E. coli cells. Descendant cells are rapidly washed away as well as components secreted by growing cells. Experiments show excellent growth rates, indicating high cell viability. Analyses of elongation and growth rates as well as morphology were successfully performed. This device will find application in prokaryotic single-cell studies under constant environment where by-product interference is undesired. Full article

(This article belongs to the Special Issue Micro/Nanofluidic Devices for Single Cell Analysis)

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