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Special Issue "Selected Papers from the 1st International Conference on Microfluidic Handling Systems"

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A special issue of Micromachines (ISSN 2072-666X).

Deadline for manuscript submissions: closed (15 December 2012)

Special Issue Editors

Guest Editor
Prof. Dr. Joost Lötters (Website)

1 Transducers Science and Technology (TST), MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
2 Bronkhorst High-Tech BV, Nijverheidsstraat 1A, 7261 AK Ruurlo, The Netherlands
Interests: Design, modelling, fabrication and application of microfluidic handling systems, including MEMS thermal and Coriolis flow sensors and controllers, MEMS pressure sensors, MEMS control valves and micromachined flow analysis sytems such as multiparameter flow measurement systems and micro Wobbe index meters
Guest Editor
Prof. Dr. Gerald A. Urban (Website)

Sensor Technology, IMTEK, Department of Microsystems Engineering, University of Freiburg, Georges Koehler Allee 103, 79110 Freiburg, Germany
Interests: microbiosensorarrays; lab-on-chip; electrophoresis on chip; thermal MEMS; nanostructured surfaces; biocompatible surfaces; biomedical in-vivo sensors; immunochips; RNA-analytics on chip

Special Issue Information

Dear Colleagues,

This special issue will publish selected papers from the 1st International Conference on Microfluidic Handling Systems (http://www.utwente.nl/ewi/mfhs2012/), 10 to 12 October 2012, Enschede, The Netherlands. Manuscripts submitted to journal Micromachines should be extended at least 40% compared with the conference one.

Worldwide, accurate handling (e.g. dosing, measurement and control) of small and extremely small mass flow rates of both gases and liquids is becoming more and more important, driven by numerous economically important applications in for instance semiconductor industry, analytical instrumentation, food, pharmacy, energy, bioanalytical systems, and micro reaction systems.

The focus of this conference is mainly on the technology, components, devices and systems that enable the application and biology in microfluidic systems. We invite submission of papers on systems and devices for accurate handling (e.g. dosing, measurement and control) of (extremely) small mass flow rates of both gases and liquids, and corresponding measurement and control principles:

  • Thermal, ultrasonic and Coriolis principles for flow measurement
  • The piezo-electric, electromagnetic and electrostatic principles for flow control
  • Electronic instrumentation
  • Application proposals
  • Innovative methods in calibration equipment and methodology
  • Micro- and nanomachining
  • Device characterization

The topics include but are not limited to:

  • Sensors: flow, pressure, viscosity, temperature, conductivity, heat capacity, density
  • Actuators: valves, pumps, mixers, droplet generators
  • Interfaces: electronic instrumentation, interconnections, assembly, technology
  • Fluidic control systems: mass flow controllers, precision mixing, dosing and dispensing, calibration
  • Applications: gas chromatographs, liquid chromatographs, medical analyses, micro reaction systems, bio-analytical systems

Dr. Joost Lötters
Prof. Dr. Gerald A. Urban
Guest Editor

Related Special Issue

Published Papers (10 papers)

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Research

Open AccessArticle Active and Precise Control of Microdroplet Division Using Horizontal Pneumatic Valves in Bifurcating Microchannel
Micromachines 2013, 4(2), 197-205; doi:10.3390/mi4020197
Received: 2 February 2013 / Revised: 21 April 2013 / Accepted: 2 May 2013 / Published: 7 May 2013
Cited by 3 | PDF Full-text (1636 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a microfluidic system for the active and precise control of microdroplet division in a micro device. Using two horizontal pneumatic valves formed at downstream of bifurcating microchannel, flow resistances of downstream channels were variably controlled. With the resistance control, [...] Read more.
This paper presents a microfluidic system for the active and precise control of microdroplet division in a micro device. Using two horizontal pneumatic valves formed at downstream of bifurcating microchannel, flow resistances of downstream channels were variably controlled. With the resistance control, volumetric ratio of downstream flows was changed and water-in-oil microdroplets were divided into two daughter droplets of different volume corresponding to the ratio. The microfluidic channels and pneumatic valves were fabricated by single-step soft lithography process of PDMS (polydimethylsiloxane) using SU-8 mold. A wide range control of the daughter droplets’ volume ratio was achieved by the simple channel structure. Volumetric ratio between large and small daughter droplets are ranged from 1 to 70, and the smallest droplet volume of 14 pL was obtained. The proposed microfluidic device is applicable for precise and high throughput droplet based digital synthesis. Full article
Open AccessArticle Pushing the Limits of Electrical Detection of Ultralow Flows in Nanofluidic Channels
Micromachines 2013, 4(2), 138-148; doi:10.3390/mi4020138
Received: 11 December 2012 / Revised: 30 January 2013 / Accepted: 20 March 2013 / Published: 2 April 2013
Cited by 11 | PDF Full-text (1223 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents improvements in flow detection by electrical cross-correlation spectroscopy. This new technique detects molecular number fluctuations of electrochemically active analyte molecules as they are transported by liquid flow through a nanochannel. The fluctuations are used as a marker of liquid [...] Read more.
This paper presents improvements in flow detection by electrical cross-correlation spectroscopy. This new technique detects molecular number fluctuations of electrochemically active analyte molecules as they are transported by liquid flow through a nanochannel. The fluctuations are used as a marker of liquid flow as their time of flight in between two consecutive transducers is determined, thereby allowing for the measurement of liquid flow rates in the picoliter-per-minute regime. Here we show an enhanced record-low sensitivity below 1 pL/min by capitalizing on improved electrical instrumentation, an optimized sensor geometry and a smaller channel cross section. We further discuss the impact of sensor geometry on the cross-correlation functions. Full article
Figures

Open AccessArticle Microbeads for Sampling and Mixing in a Complex Sample
Micromachines 2013, 4(1), 103-115; doi:10.3390/mi4010103
Received: 21 January 2013 / Revised: 4 March 2013 / Accepted: 5 March 2013 / Published: 19 March 2013
Cited by 5 | PDF Full-text (668 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents work on the development of a microfluidic device using super-paramagnetic beads for sampling and mixing. The beads are manipulated via an external rotating permanent magnet in a microfluidic channel. Efficient mixing is achieved in a short distance with this [...] Read more.
This paper presents work on the development of a microfluidic device using super-paramagnetic beads for sampling and mixing. The beads are manipulated via an external rotating permanent magnet in a microfluidic channel. Efficient mixing is achieved in a short distance with this method. Modeling shows the variables which influence the mixing are flow rate, bead rotation speed and the bead number density. Displacement of the bead relative the rotating magnetic field sets an upper limit on the bead rotation speed due to viscous drag. Future work will examine optimization of this system for capture of pathogens from a complex mixture. Full article
Open AccessArticle Tunable Sensor Response by Voltage-Control in Biomimetic Hair Flow Sensors
Micromachines 2013, 4(1), 116-127; doi:10.3390/mi4010116
Received: 13 December 2012 / Revised: 7 March 2013 / Accepted: 8 March 2013 / Published: 19 March 2013
Cited by 3 | PDF Full-text (687 KB) | HTML Full-text | XML Full-text
Abstract
We presented an overview of improvements in detection limit and responsivity of our biomimetic hair flow sensors by electrostatic spring-softening (ESS). Applying a DC-bias voltage to our capacitive flow sensors improves the responsively by up to 80% for flow signals at frequencies [...] Read more.
We presented an overview of improvements in detection limit and responsivity of our biomimetic hair flow sensors by electrostatic spring-softening (ESS). Applying a DC-bias voltage to our capacitive flow sensors improves the responsively by up to 80% for flow signals at frequencies below the sensor’s resonance. Application of frequency matched AC-bias voltages allows for tunable filtering and selective gain up to 20 dB. Furthermore, the quality and fidelity of low frequency flow measurements can be improved using a non frequency-matched AC-bias voltage, resulting in a flow detection limit down to 5 mm/s at low (30 Hz) frequencies. The merits and applicability of the three methods are discussed. Full article
Open AccessArticle Active Continuous-Flow Micromixer Using an External Braille Pin Actuator Array
Micromachines 2013, 4(1), 80-89; doi:10.3390/mi4010080
Received: 17 December 2012 / Revised: 11 February 2013 / Accepted: 1 March 2013 / Published: 14 March 2013
Cited by 6 | PDF Full-text (826 KB) | HTML Full-text | XML Full-text
Abstract
We present a continuous-flow active micromixer based on channel-wall deflection in a polydimethylsiloxane (PDMS) chip for volume flows in the range up to 2 μL s−1 which is intended as a novel unit operation for the microfluidic Braille pin actuated platform. The [...] Read more.
We present a continuous-flow active micromixer based on channel-wall deflection in a polydimethylsiloxane (PDMS) chip for volume flows in the range up to 2 μL s−1 which is intended as a novel unit operation for the microfluidic Braille pin actuated platform. The chip design comprises a main microchannel connected to a series of side channels with dead ends aligned on the Braille pins. Computer-controlled deflection of the side-channel walls induces chaotic advection in the main-channel, which substantially accelerates mixing in low-Reynolds number flow. Sufficient mixing (mixing index MI below 0.1) of volume flows up to 0.5 μL s−1 could be achieved within residence times ~500 ms in the micromixer. As an application, continuous dilution of a yeast cell sample by a ratio down to 1:10 was successfully demonstrated. The mixer is intended to serve as a component of bio-analytical devices or as a unit operation in the microfluidic Braille pin actuated platform. Full article
Figures

Open AccessArticle Enhanced Liquid Metal Micro Droplet Generation by Pneumatic Actuation Based on the StarJet Method
Micromachines 2013, 4(1), 49-66; doi:10.3390/mi4010049
Received: 5 December 2012 / Revised: 4 February 2013 / Accepted: 4 February 2013 / Published: 11 March 2013
Cited by 6 | PDF Full-text (1978 KB) | HTML Full-text | XML Full-text
Abstract
We present a novel pneumatic actuation system for generation of liquid metal droplets according to the so-called StarJet method. In contrast to our previous work, the performance of the device has been significantly improved: the maximum droplet generation frequency in continuous mode [...] Read more.
We present a novel pneumatic actuation system for generation of liquid metal droplets according to the so-called StarJet method. In contrast to our previous work, the performance of the device has been significantly improved: the maximum droplet generation frequency in continuous mode has been increased to fmax = 11 kHz (formerly fmax = 4 kHz). In addition, the droplet diameter has been reduced to 60 μm. Therefore, a new fabrication process for the silicon nozzle chips has been developed enabling the production of smaller nozzle chips with higher surface quality. The size of the metal reservoir has been increased to hold up to 22 mL liquid metal and the performance and durability of the actuator has been improved by using stainless steel and a second pneumatic connection to control the sheath flow. Experimental results are presented regarding the characterization of the droplet generation, as well as printed metal structures. Full article
Open AccessArticle Controllable Active Micro Droplets Merging Device Using Horizontal Pneumatic Micro Valves
Micromachines 2013, 4(1), 34-48; doi:10.3390/mi4010034
Received: 14 December 2012 / Revised: 31 January 2013 / Accepted: 8 February 2013 / Published: 8 March 2013
Cited by 2 | PDF Full-text (1460 KB) | HTML Full-text | XML Full-text
Abstract
We present an active droplet merging device, which can merge various sizes of micro droplets in different numbers by using pneumatically controlled horizontal PDMS microvalves. The merging part consists of a main and side channels separated by a pillar array. The pillar [...] Read more.
We present an active droplet merging device, which can merge various sizes of micro droplets in different numbers by using pneumatically controlled horizontal PDMS microvalves. The merging part consists of a main and side channels separated by a pillar array. The pillar array structure is contained within a microfuidic channel. The function of the pillar array provides a bypass path to the continuous flow (oil) inside the merging chamber. Droplets are successfully generated within the channel and achieve merging by controlling the selective different numbers and diameters of droplets through varying the flow resistance of main and side channel. In the merging chamber, a droplet will enter and slow down its movement. It will wait and then merge with the sequential droplets. These experiments demonstrate that such a merging device can controllably select and adjust the distance between the different adjacent micro droplets without any generation of sister droplets in the side channel. The device has no desynchronization problems. Thus, it can be applied for efficiently mixing the droplets in various diameters and numbers without changing the structure of the merging chamber. Hence, this device can be a more effective choice when applying microfluidics to chemical and biological applications. Full article
Open AccessArticle Compact Mass Flow Meter Based on a Micro Coriolis Flow Sensor
Micromachines 2013, 4(1), 22-33; doi:10.3390/mi4010022
Received: 17 December 2012 / Revised: 5 February 2013 / Accepted: 8 February 2013 / Published: 1 March 2013
Cited by 8 | PDF Full-text (787 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we demonstrate a compact ready-to-use micro Coriolis mass flow meter. The full scale flow is 1 g/h (for water at a pressure drop < 1 bar). It has a zero stability of 2 mg/h and an accuracy of 0.5% [...] Read more.
In this paper we demonstrate a compact ready-to-use micro Coriolis mass flow meter. The full scale flow is 1 g/h (for water at a pressure drop < 1 bar). It has a zero stability of 2 mg/h and an accuracy of 0.5% reading for both liquids and gases. The temperature drift between 10 and 50 °C is below 1 mg/h/°C. The meter is robust, has standard fluidic connections and can be read out by means of a PC or laptop via USB. Its performance was tested for several common gases (hydrogen, helium, nitrogen, argon and air) and liquids (water and isopropanol). As in all Coriolis mass flow meters, the meter is also able to measure the actual density of the medium flowing through the tube. The sensitivity of the measured density is ~1 Hz.m3/kg. Full article
Open AccessArticle A Low-Cost, Normally Closed, Solenoid Valve for Non-Contact Dispensing in the Sub-µL Range
Micromachines 2013, 4(1), 9-21; doi:10.3390/mi4010009
Received: 11 December 2012 / Revised: 4 February 2013 / Accepted: 4 February 2013 / Published: 28 February 2013
Cited by 5 | PDF Full-text (873 KB) | HTML Full-text | XML Full-text
Abstract
We present a disposable, normally closed, non-contact dispensing valve for the sub-µL range. The miniaturized solenoid valve (diameter: 8 mm, height: 27.25 mm) is compatible to standard Luer-Lock interfaces. A highly dynamic actuation principle enables opening times down to 1 ms. The [...] Read more.
We present a disposable, normally closed, non-contact dispensing valve for the sub-µL range. The miniaturized solenoid valve (diameter: 8 mm, height: 27.25 mm) is compatible to standard Luer-Lock interfaces. A highly dynamic actuation principle enables opening times down to 1 ms. The dispensing performance was evaluated for water (η = 1.03 mPas) and a 66% (w/w) glycerol/water solution (η = 16.98 mPas), at pressures varying from 200 to 800 mbar. The experimentally determined minimal dispensing volume was 163 nL (CV 1.6%) for water and 123 nL (CV 4.5%) for 66% (w/w) glycerol/water. The low-cost polymer valve enables high precision dispensing of liquid volumes down to the lower end of the sub-µL range comparable to high-end non-disposable micro-dispensing valves. Full article
Figures

Open AccessArticle Advanced Capillary Soft Valves for Flow Control in Self-Driven Microfluidics
Micromachines 2013, 4(1), 1-8; doi:10.3390/mi4010001
Received: 27 November 2012 / Revised: 14 January 2013 / Accepted: 17 January 2013 / Published: 24 January 2013
Cited by 3 | PDF Full-text (861 KB) | HTML Full-text | XML Full-text
Abstract
Self-driven microfluidic devices enable fully autonomous handling of very small volumes of liquid samples and reagents. However, many applications require an active control mechanism to trigger self-driven flow in microchannels. Here, we report on capillary soft valves (CSVs), which enable stopping a [...] Read more.
Self-driven microfluidic devices enable fully autonomous handling of very small volumes of liquid samples and reagents. However, many applications require an active control mechanism to trigger self-driven flow in microchannels. Here, we report on capillary soft valves (CSVs), which enable stopping a liquid filling front at a precise location inside a microchannel and can resume flow of liquid upon simple actuation. The working mechanism of a CSV is based on a barrier of capillary pressure induced by an abruptly expanding microchannel. We discuss the influence of wetting conditions on the performance of a CSV and the effect of elevated temperatures on a CSV in its closed state. We introduce design features such as pillars and cavities, as well as fabrication techniques for rounded microchannels, which all may broaden the applicability and robustness of CSVs in microfluidic devices. Finally, we present CSV having multiple inlet channels. CSVs further diversify the toolbox of microfluidic functionalities and yet are simple to implement, fabricate and actuate. Full article

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