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Special Issue "Microactuators"

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

Deadline for manuscript submissions: closed (30 September 2014)

Special Issue Editor

Guest Editor
Prof. Dr. Ulrike Wallrabe

Laboratory for Microactuators IMTEK—Department of Microsystems Engineering University of Freiburg Georges-Koehler-Allee 102 79110 Freiburg, Germany
Website | E-Mail
Fax: +49 761 203 7439
Interests: microactuators; magnetic microsystems; micro coils; piezo actuators; Optical MEMS; adaptive micro optics; micro MRI (magneto resonance imaging); microsystems in neurosciences; energy harvesting

Special Issue Information

Dear Colleagues,

Looking back at thirty years of microsystem development, micro actuators have proved themselves to be the key elements for almost all kinds of microsystems. Hardly found as stand-alone components, they are typically integrated into systems. The most obvious example, and simultaneously the most popular device, is the electrostatic comb actuator, which is found as an integrated part of innumerous inertial sensors. Its unique success is due to its simple and scalable design, and its reliable integrated manufacturing process via the ICP. In addition, magnetic, piezoelectric, shape memory, pneumatic, and hydraulic principles have been explored for micro actuation, each of which have its own limits of integration, process complexity, and applicability. Also, over the past few years, living cells, such as cardio myocytes, muscle cells, and whole dorsal vessels, have been combined with technical systems and have resulted in new types of bio micro actuators. However, most of them problematically require an aqueous environment and only have a limited lifetime.

There potential applications of micro actuators are wide-ranging and include inertial sensors, optical MEMS and lab-on-a-chip, manipulators, micro robots, and micro surgery. Each domain has its typical requirements in terms of forces, displacements, materials, frequencies, voltage vs. current control, etc.

For this Special Issue, we encourage reviews on actuation mechanism classes and classes of application. We also encourage the submission of regular papers on new actuators.

Prof. Dr. Ulrike Wallrabe
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs).

Keywords

  • micro actuator
  • nano actuator
  • electrostatic magnetic
  • piezo electric
  • shape memory
  • electro wetting
  • cells
  • pumps
  • switches
  • optical MEMS
  • micro robots
  • grippers
  • endoscopes
  • micro surgery

Published Papers (6 papers)

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Research

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Open AccessArticle Performance Characterization of Micromachined Inductive Suspensions Based on 3D Wire-Bonded Microcoils
Micromachines 2014, 5(4), 1469-1484; doi:10.3390/mi5041469
Received: 30 September 2014 / Revised: 1 December 2014 / Accepted: 5 December 2014 / Published: 12 December 2014
Cited by 3 | PDF Full-text (8989 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We present a comprehensive experimental investigation of a micromachined inductive suspension (MIS) based on 3D wire-bonded microcoils. A theoretical model has been developed to predict the levitation height of the disc-shaped proof mass (PM), which has good agreement with the experimental results. The
[...] Read more.
We present a comprehensive experimental investigation of a micromachined inductive suspension (MIS) based on 3D wire-bonded microcoils. A theoretical model has been developed to predict the levitation height of the disc-shaped proof mass (PM), which has good agreement with the experimental results. The 3D MIS consists of two coaxial wire-bonded coils, the inner coil being used for levitation, while the outer coil for the stabilization of the PM. The levitation behavior is mapped with respect to the input parameters of the excitation currents applied to the levitation and stabilization coil, respectively: amplitude and frequency. At the same time, the levitation is investigated with respect to various thickness values (12.5 to 50 μm) and two materials (Al and Cu) of the proof mass. An important characteristic of an MIS, which determines its suitability for various applications, such as, e.g., micro-motors, is the dynamics in the lateral direction. We experimentally study the lateral stabilization force acting on the PM as a function of the linear displacement. The analysis of this dependency allows us to define a transition between stable and unstable levitation behavior. From an energetic point of view, this transition corresponds to the local maximum of the MIS potential energy. 2D simulations of the potential energy help us predict the location of this maximum, which is proven to be in good agreement with the experiment. Additionally, we map the temperature distribution for the coils, as well as for the PM levitated at 120 μm, which confirms the significant reduction of the heat dissipation in the MIS based on 3D microcoils compared to the planar topology. Full article
(This article belongs to the Special Issue Microactuators)
Figures

Open AccessArticle SU-8 Electrothermal Actuators: Optimization of Fabrication and Excitation for Long-Term Use
Micromachines 2014, 5(4), 1310-1322; doi:10.3390/mi5041310
Received: 2 October 2014 / Revised: 14 November 2014 / Accepted: 21 November 2014 / Published: 2 December 2014
Cited by 5 | PDF Full-text (4684 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we examine the suitability of SU-8 2000 as a construction material for electrothermal actuators and the actuator stability for long-term operation. The fabrication of SU-8 was optimized for mechanical and thermal stability. Samples with different softbake duration, exposure dose and
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In this paper we examine the suitability of SU-8 2000 as a construction material for electrothermal actuators and the actuator stability for long-term operation. The fabrication of SU-8 was optimized for mechanical and thermal stability. Samples with different softbake duration, exposure dose and postbake temperature were evaluated using Fourier-Transform IR-spectroscopy and dynamic-mechanical analysis. The exposure dose and postbake temperature proved to have a strong influence on the cross-linking and the glass transition temperature. A final hardbake levels the effects of the process history. A high degree of crosslinking, a low drop of the dynamic modulus over temperature (30%) up to the glass transition temperature 100–140 °C were achieved for SU-8 with an exposure dose of 1500 mJ/cm², a postbake temperature of 95 °C and hardbake of 240 °C. Electrothermal actuators proved to be stable until the end of the experiment after 2400 duty cycles. Actuator deflections up to 55 μm were measured (actuator length: 4 mm) for input powers up to 160 mW and a maximum operating temperature of 120 °C. Higher temperatures led to permanent deformations and failure. An offset drift of up to 20% occurs during actuation, but converges after a burn-in phase of about two hours. Full article
(This article belongs to the Special Issue Microactuators)
Figures

Open AccessArticle Motility Control of Bacteria-Actuated Biodegradable Polymeric Microstructures by Selective Adhesion Methods
Micromachines 2014, 5(4), 1287-1295; doi:10.3390/mi5041287
Received: 21 August 2014 / Revised: 14 November 2014 / Accepted: 21 November 2014 / Published: 28 November 2014
Cited by 3 | PDF Full-text (2693 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Certain bacteria have motility and can be made non-toxic, and using them for drug delivery has been proposed. For example, using bacteria with flagella motion in multiple spin actuators in drug delivery microrobots has been suggested. This paper investigates various adhesion enhancement methods
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Certain bacteria have motility and can be made non-toxic, and using them for drug delivery has been proposed. For example, using bacteria with flagella motion in multiple spin actuators in drug delivery microrobots has been suggested. This paper investigates various adhesion enhancement methods for attaching bacteria on preferred surfaces of cubic polymeric microstructures to achieve the directional control of motion. Serratia marcescens which has an excellent swimming behavior and 50-μm sized cubic structures made of biodegradable poly-capro-lactone (PCL) are used. Three treatment methods are investigated and compared to the untreated control case. The first method is retarding bacterial attachments by coating certain surfaces with bovine serum albumin (BSA) which makes those surfaces anti-adherent to bacteria. The second and third methods are roughening the surfaces with X-ray irradiation and plasma respectively to purposely increase bacterial attachments on the roughened surfaces. The measured motilities of bacteria-tethered PCL microactuators are 1.40 μm/s for the BSA coating method, 0.82 μm/s for the X-ray irradiation, and 3.89 μm/s for the plasma treatment method. Therefore, among the methods investigated in the paper the plasma treatment method achieves the highest directionality control of bacteria motility. Full article
(This article belongs to the Special Issue Microactuators)
Open AccessArticle Structural Design and Experimental Analysis of a Piezoelectric Vibration Feeder with a Magnetic Spring
Micromachines 2014, 5(3), 547-557; doi:10.3390/mi5030547
Received: 25 June 2014 / Revised: 2 August 2014 / Accepted: 5 August 2014 / Published: 19 August 2014
Cited by 1 | PDF Full-text (2461 KB) | HTML Full-text | XML Full-text
Abstract
A piezoelectric vibration feeder with a magnetic spring is discussed in this paper. The feeder can keep resonance frequency relatively stable under changing loading. Through the analysis on the working principle and magnetic spring stiffness characteristic of this feeder, the dynamic model was
[...] Read more.
A piezoelectric vibration feeder with a magnetic spring is discussed in this paper. The feeder can keep resonance frequency relatively stable under changing loading. Through the analysis on the working principle and magnetic spring stiffness characteristic of this feeder, the dynamic model was established and the relationship among system resonance frequency, loading and magnetic spring stiffness was obtained. The analysis showed that, as the loading changed, the magnetic spring stiffness changed accordingly, which maintained a trend of stability in the system resonance frequency. A prototype was made for the experiment, and the relationship among the loading, magnetic spring axial clearance and system resonance frequency was obtained. The result showed that, when the loading changes, the resonance frequency and feeding speed tended to be stable, which matched the theoretical analysis. Through comparison with a traditional vibration feeder, within nominal loading, this new feeder has more stable resonance frequency and feeding speed. Full article
(This article belongs to the Special Issue Microactuators)

Review

Jump to: Research

Open AccessReview Magnetic Shape Memory Microactuators
Micromachines 2014, 5(4), 1135-1160; doi:10.3390/mi5041135
Received: 29 September 2014 / Revised: 1 November 2014 / Accepted: 1 November 2014 / Published: 18 November 2014
Cited by 7 | PDF Full-text (5288 KB) | HTML Full-text | XML Full-text
Abstract
By introducing smart materials in micro systems technologies, novel smart microactuators and sensors are currently being developed, e.g., for mobile, wearable, and implantable MEMS (Micro-electro-mechanical-system) devices. Magnetic shape memory alloys (MSMAs) are a promising material system as they show multiple coupling effects as
[...] Read more.
By introducing smart materials in micro systems technologies, novel smart microactuators and sensors are currently being developed, e.g., for mobile, wearable, and implantable MEMS (Micro-electro-mechanical-system) devices. Magnetic shape memory alloys (MSMAs) are a promising material system as they show multiple coupling effects as well as large, abrupt changes in their physical properties, e.g., of strain and magnetization, due to a first order phase transformation. For the development of MSMA microactuators, considerable efforts are undertaken to fabricate MSMA foils and films showing similar and just as strong effects compared to their bulk counterparts. Novel MEMS-compatible technologies are being developed to enable their micromachining and integration. This review gives an overview of material properties, engineering issues and fabrication technologies. Selected demonstrators are presented illustrating the wide application potential. Full article
(This article belongs to the Special Issue Microactuators)
Open AccessReview Electromagnetic Micromotors—Design, Fabrication and Applications
Micromachines 2014, 5(4), 929-942; doi:10.3390/mi5040929
Received: 24 September 2014 / Accepted: 20 October 2014 / Published: 24 October 2014
PDF Full-text (3664 KB) | HTML Full-text | XML Full-text
Abstract
Microactuators have become essential elements of microelectromechanical systems, for example, for positioning purposes and for fluid-handling tasks in microfluidic systems. UV depth lithography and other new micromachining technologies, which have been developed since the 1990s, have initiated extensive investigations of electromagnetic microactuators, which
[...] Read more.
Microactuators have become essential elements of microelectromechanical systems, for example, for positioning purposes and for fluid-handling tasks in microfluidic systems. UV depth lithography and other new micromachining technologies, which have been developed since the 1990s, have initiated extensive investigations of electromagnetic microactuators, which are characterized by high forces, large deflections, low driving voltages resulting from low input impedances and robustness under harsh environments. This paper reviews the comprehensive research on the design, fabrication and application of electromagnetic micromotors performed in our laboratory over the past years. Full article
(This article belongs to the Special Issue Microactuators)

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