Special Issue "Polymer Based MEMS and Microfabrication"

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "D:Materials and Processing".

Deadline for manuscript submissions: closed (15 August 2018).

Special Issue Editor

Prof. Dan Sameoto
E-Mail Website
Guest Editor
Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada
Interests: microfabrication; polymers; lab-on-a-chip; MEMS; biomimetic adhesives; composites; additive manufacturing
Special Issues and Collections in MDPI journals

Special Issue Information

Dear colleagues,

The use of polymers in microfabrication has become increasingly important, with applications ranging from microfluidic systems, neural probes, microrobotics and biomimetic materials all benefiting from the unique manufacturing options and material properties available with polymers in comparison to traditional silicon based microfabrication. In this Special Issue, we aim to highlight some of the recent application of polymers in MEMS, microfluidics and smart materials applications, as well as unique fabrication methods that integrate electrical and mechanical functionality with flexible, stretchable, biocompatible, or disposable devices. Challenges in fabrication reliability, scalable production, and integration with other microfabrication technologies are still being addressed by researchers and companies around the world and solutions to these challenges are expected to permit polymers to be used in a much wider variety of microfabricated products in the future. We invite research papers, reviews and shorter communications that focus on the use of polymers in microfabricated products that combine either sensing or actuation features common to MEMS. Topics of particular interest include, but are not limited to, micromanufacturing of polymer based sensors and actuators, microrobotic systems, novel fabrication processes and polymer materials, stretchable electronics, microinjection molded products, biocompatibility of polymer MEMS, polymer microfluidic systems, and additive manufacturing of MEMS.

Prof. Dan Sameoto
Guest Editor

Manuscript Submission Information

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. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short 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.

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Polymers

  • Microfabrication

  • MEMS

  • Microfluidics

  • Biomimetics

  • Composites

  • Microrobotics

Published Papers (12 papers)

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Editorial

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Open AccessEditorial
Editorial for the Special Issue on Polymer Based MEMS and Microfabrication
Micromachines 2019, 10(1), 49; https://doi.org/10.3390/mi10010049 - 11 Jan 2019
Abstract
Polymers are becoming increasingly important in MEMS and microfabricated products [...] Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)

Research

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Open AccessFeature PaperArticle
Fluorosilicone as an Omnimold for Microreplication
Micromachines 2018, 9(8), 406; https://doi.org/10.3390/mi9080406 - 16 Aug 2018
Cited by 1
Abstract
Soft lithography and replica molding have been an integral part of polymer basic microfabrication for over 20 years. The use of silicone rubber materials as either molds or directly molded parts are well described in the literature and have provided researchers with an [...] Read more.
Soft lithography and replica molding have been an integral part of polymer basic microfabrication for over 20 years. The use of silicone rubber materials as either molds or directly molded parts are well described in the literature and have provided researchers with an easily accessible technique to reproduce complex micro and nanostructures with minimal costs and technical challenges. Yet, for many applications, the use of standard silicones may not necessarily be the best choice, either as a mold material or as a replicated surface. For those instances where a mold is required that is high temperature tolerant, flexible, durable and capable of being used as a mold for multiple materials including silicone rubber, the most commonly used silicone rubber, Sylgard-184, has substantial deficiencies. In this work, we introduce a new material, Fluorosilicone that has not been described in the microfabrication field in detail and determine it is capable of reproducing micro structures via soft lithography techniques and being used as a mold for thermoplastic and thermosetting polymers, including silicone rubbers. Material compatibility, appropriate processing conditions for quality replicas and demonstration of extremely fast production of silicone microstructures are reported. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessFeature PaperArticle
Micro-Dumbbells—A Versatile Tool for Optical Tweezers
Micromachines 2018, 9(6), 277; https://doi.org/10.3390/mi9060277 - 01 Jun 2018
Cited by 3
Abstract
Manipulation of micro- and nano-sized objects with optical tweezers is a well-established, albeit still evolving technique. While many objects can be trapped directly with focused laser beam(s), for some applications indirect manipulation with tweezers-operated tools is preferred. We introduce a simple, versatile micro-tool [...] Read more.
Manipulation of micro- and nano-sized objects with optical tweezers is a well-established, albeit still evolving technique. While many objects can be trapped directly with focused laser beam(s), for some applications indirect manipulation with tweezers-operated tools is preferred. We introduce a simple, versatile micro-tool operated with holographic optical tweezers. The 40 µm long dumbbell-shaped tool, fabricated with two-photon laser 3D photolithography has two beads for efficient optical trapping and a probing spike on one end. We demonstrate fluids viscosity measurements and vibration detection as examples of possible applications. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle
CO2 Laser-Based Rapid Prototyping of Micropumps
Micromachines 2018, 9(5), 215; https://doi.org/10.3390/mi9050215 - 03 May 2018
Cited by 3
Abstract
The fabrication of microdevices for fluidic control often requires the use of flexible diaphragms in a way that requires cleanroom equipment and compromises performance. We use a CO 2 laser to perform the standard ablative techniques of cutting and engraving materials, but we [...] Read more.
The fabrication of microdevices for fluidic control often requires the use of flexible diaphragms in a way that requires cleanroom equipment and compromises performance. We use a CO 2 laser to perform the standard ablative techniques of cutting and engraving materials, but we also apply a method that we call laser placement. This allows us to fabricate precisely-positioned and precisely-sized, isolated diaphragms. This in turn enables the rapid prototyping of integrated multilayer microfluidic devices to form complex structures without the need for manual positioning or cleanroom equipment. The fabrication process is also remarkably rapid and capable of being scaled to manufacturing levels of production. We explore the use of these devices to construct a compact system of peristaltic pumps that can form water in oil droplets without the use of the non-pulsatile pumping systems typically required. Many devices can be fabricated at a time on a sheet by sheet basis with a fabrication process that, to our knowledge, is the fastest reported to date for devices of this type (requiring only 3 h). Moreover, this system is unusually compact and self-contained. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle
Study of the Carrier-Aided Thin Film Electrode Array Design for Cochlear Insertion
Micromachines 2018, 9(5), 206; https://doi.org/10.3390/mi9050206 - 27 Apr 2018
Cited by 2
Abstract
The micro-fabricated thin film electrode array (TFEA) has been a promising design for cochlear implants (CIs) because of its cost-effectiveness and fabrication precision. The latest polymer-based cochlear TFEAs have faced difficulties for cochlear insertion due to the lack of structural stiffness. To stiffen [...] Read more.
The micro-fabricated thin film electrode array (TFEA) has been a promising design for cochlear implants (CIs) because of its cost-effectiveness and fabrication precision. The latest polymer-based cochlear TFEAs have faced difficulties for cochlear insertion due to the lack of structural stiffness. To stiffen the TFEA, dissolvable stiffening materials, TFEAs with different structures, and TFEAs with commercial CIs as carriers have been invested. In this work, the concept of enhancing a Parylene TFEA with Kapton tape as a simpler carrier for cochlear insertion has been proved to be feasible. The bending stiffness of the Kapton-aided TFEA was characterized with an analytical model, a finite element model, and a cantilever bending experiment, respectively. While the Kapton tape increased the bending stiffness of the Parylene TFEA by 103 times, the 6-μm-thick TFEA with a similar Young’s modulus, as a polyimide, in turn significantly increased the bending stiffness of the 170-μm-thick Kapton carrier by 60%. This result indicated that even the TFEA is ultra-flexible and that its bending stiffness should not be neglected in the design or selection of its carrier. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle
Flexible Tactile Sensor Array Based on Aligned MWNTs-PU Composited Sub-Microfibers
Micromachines 2018, 9(5), 201; https://doi.org/10.3390/mi9050201 - 24 Apr 2018
Cited by 1
Abstract
This present paper describes a novel method to fabricate tactile sensor arrays by producing aligned multi-walled carbon nanotubes (MWNTs)-polyurethane (PU) composite sub-microfiber (SMF) arrays with the electrospinning technique. The proposed sensor was designed to be used as the artificial skin for a tactile [...] Read more.
This present paper describes a novel method to fabricate tactile sensor arrays by producing aligned multi-walled carbon nanotubes (MWNTs)-polyurethane (PU) composite sub-microfiber (SMF) arrays with the electrospinning technique. The proposed sensor was designed to be used as the artificial skin for a tactile sensation system. Although thin fibers in micro- and nanoscale have many good mechanical characteristics and could enhance the alignment of MWNTs inside, the high impedance as a consequence of a small section handicaps its application. In this paper, unidirectional composite SMFs were fabricated orthogonally to the parallel electrodes through a low-cost method to serve as sensitive elements (SEs), and the impedances of SEs were measured to investigate the changes with deformation caused by applied force. The particular piezoresistive mechanism of MWNTs disturbed in SMF was analyzed. The static and dynamic test results of the fabricated tactile sensor were also presented to validate the performance of the proposed design. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle
SF6 Optimized O2 Plasma Etching of Parylene C
Micromachines 2018, 9(4), 162; https://doi.org/10.3390/mi9040162 - 02 Apr 2018
Cited by 2
Abstract
Parylene C is a widely used polymer material in microfabrication because of its excellent properties such as chemical inertness, biocompatibility and flexibility. It has been commonly adopted as a structural material for a variety of microfluidics and bio-MEMS (micro-electro-mechanical system) applications. However, it [...] Read more.
Parylene C is a widely used polymer material in microfabrication because of its excellent properties such as chemical inertness, biocompatibility and flexibility. It has been commonly adopted as a structural material for a variety of microfluidics and bio-MEMS (micro-electro-mechanical system) applications. However, it is still difficult to achieve a controllable Parylene C pattern, especially on film thicker than a couple of micrometers. Here, we proposed an SF6 optimized O2 plasma etching (SOOE) of Parylene C, with titanium as the etching mask. Without the SF6, noticeable nanoforest residuals were found on the O2 plasma etched Parylene C film, which was supposed to arise from the micro-masking effect of the sputtered titanium metal mask. By introducing a 5-sccm SF6 flow, the residuals were effectively removed during the O2 plasma etching. This optimized etching strategy achieved a 10 μm-thick Parylene C etching with the feature size down to 2 μm. The advanced SOOE recipes will further facilitate the controllable fabrication of Parylene C microstructures for broader applications. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle
3D Printing, Ink Casting and Micromachined Lamination (3D PICLμM): A Makerspace Approach to the Fabrication of Biological Microdevices
Micromachines 2018, 9(2), 85; https://doi.org/10.3390/mi9020085 - 15 Feb 2018
Cited by 10
Abstract
We present a novel benchtop-based microfabrication technology: 3D printing, ink casting, micromachined lamination (3D PICLμM) for rapid prototyping of lab-on-a-chip (LOC) and biological devices. The technology uses cost-effective, makerspace-type microfabrication processes, all of which are ideally suited for low resource settings, and utilizing [...] Read more.
We present a novel benchtop-based microfabrication technology: 3D printing, ink casting, micromachined lamination (3D PICLμM) for rapid prototyping of lab-on-a-chip (LOC) and biological devices. The technology uses cost-effective, makerspace-type microfabrication processes, all of which are ideally suited for low resource settings, and utilizing a combination of these processes, we have demonstrated the following devices: (i) 2D microelectrode array (MEA) targeted at in vitro neural and cardiac electrophysiology, (ii) microneedle array targeted at drug delivery through a transdermal route and (iii) multi-layer microfluidic chip targeted at multiplexed assays for in vitro applications. The 3D printing process has been optimized for printing angle, temperature of the curing process and solvent polishing to address various biofunctional considerations of the three demonstrated devices. We have depicted that the 3D PICLμM process has the capability to fabricate 30 μm sized MEAs (average 1 kHz impedance of 140 kΩ with a double layer capacitance of 3 μF), robust and reliable microneedles having 30 μm radius of curvature and ~40 N mechanical fracture strength and microfluidic devices having 150 μm wide channels and 400 μm fluidic vias capable of fluid mixing and transmitted light microparticle visualization. We believe our 3D PICLμM is ideally suited for applications in areas such as electrophysiology, drug delivery, disease in a dish, organ on a chip, environmental monitoring, agricultural therapeutic delivery and genomic testing. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle
Milling Positive Master for Polydimethylsiloxane Microfluidic Devices: The Microfabrication and Roughness Issues
Micromachines 2017, 8(10), 287; https://doi.org/10.3390/mi8100287 - 21 Sep 2017
Cited by 5
Abstract
We provide a facile and low-cost method (F-L) to fabricate a two-dimensional positive master using a milling technique for polydimethylsiloxane (PDMS)-based microchannel molding. This method comprises the following steps: (1) a positive microscale master of the geometry is milled on to an acrylic [...] Read more.
We provide a facile and low-cost method (F-L) to fabricate a two-dimensional positive master using a milling technique for polydimethylsiloxane (PDMS)-based microchannel molding. This method comprises the following steps: (1) a positive microscale master of the geometry is milled on to an acrylic block; (2) pre-cured PDMS is used to mold the microscale positive master; (3) the PDMS plate is peeled off from the master and punctured with a blunt needle; and (4) the PDMS plate is O2 plasma bonded to a glass slide. Using this technique, we can fabricate microchannels with very simple protocols quickly and inexpensively. This method also avoids breakage of the end mill (ϕ = 0.4 mm) of the computerized numerical control (CNC) system when fabricating the narrow channels (width < 50 µm). The prominent surface roughness of the milled bottom-layer could be overcomed by pre-cured PDMS with size trade-off in design. Finally, emulsion formation successfully demonstrates the validity of the proposed fabrication protocol. This work represents an important step toward the use of a milling technique for PDMS-based microfabrication. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessArticle
PMMA Solution Assisted Room Temperature Bonding for PMMA–PC Hybrid Devices
Micromachines 2017, 8(9), 284; https://doi.org/10.3390/mi8090284 - 20 Sep 2017
Cited by 3
Abstract
Recently, thermoplastic polymers have become popular materials for microfluidic chips due to their easy fabrication and low cost. A polymer based microfluidic device can be formed in various fabrication techniques such as laser machining, injection molding, and hot embossing. A new bonding process [...] Read more.
Recently, thermoplastic polymers have become popular materials for microfluidic chips due to their easy fabrication and low cost. A polymer based microfluidic device can be formed in various fabrication techniques such as laser machining, injection molding, and hot embossing. A new bonding process presented in this paper uses a 2.5% (w/w) polymethyl methacrylate (PMMA) solution as an adhesive layer to bond dissimilar polymers—PMMA to polycarbonate (PC)—to enclose the PMMA microfluidic channels with PC. This technique has been successfully demonstrated to bond PMMA microchip to PC film. This paper presents bonding strength using a shear strength test and a crack opening method in addition to the fluidic leakage inspection. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Review

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Open AccessFeature PaperReview
Techniques and Considerations in the Microfabrication of Parylene C Microelectromechanical Systems
Micromachines 2018, 9(9), 422; https://doi.org/10.3390/mi9090422 - 22 Aug 2018
Cited by 6
Abstract
Parylene C is a promising material for constructing flexible, biocompatible and corrosion-resistant microelectromechanical systems (MEMS) devices. Historically, Parylene C has been employed as an encapsulation material for medical implants, such as stents and pacemakers, due to its strong barrier properties and biocompatibility. In [...] Read more.
Parylene C is a promising material for constructing flexible, biocompatible and corrosion-resistant microelectromechanical systems (MEMS) devices. Historically, Parylene C has been employed as an encapsulation material for medical implants, such as stents and pacemakers, due to its strong barrier properties and biocompatibility. In the past few decades, the adaptation of planar microfabrication processes to thin film Parylene C has encouraged its use as an insulator, structural and substrate material for MEMS and other microelectronic devices. However, Parylene C presents unique challenges during microfabrication and during use with liquids, especially for flexible, thin film electronic devices. In particular, the flexibility and low thermal budget of Parylene C require modification of the fabrication techniques inherited from silicon MEMS, and poor adhesion at Parylene-Parylene and Parylene-metal interfaces causes device failure under prolonged use in wet environments. Here, we discuss in detail the promises and challenges inherent to Parylene C and present our experience in developing thin-film Parylene MEMS devices. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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Open AccessReview
Integrated Electromechanical Transduction Schemes for Polymer MEMS Sensors
Micromachines 2018, 9(5), 197; https://doi.org/10.3390/mi9050197 - 24 Apr 2018
Cited by 2
Abstract
Polymer Micro ElectroMechanical Systems (MEMS) have the potential to constitute a powerful alternative to silicon-based MEMS devices for sensing applications. Although the use of commercial photoresists as structural material in polymer MEMS has been widely reported, the integration of functional polymer materials as [...] Read more.
Polymer Micro ElectroMechanical Systems (MEMS) have the potential to constitute a powerful alternative to silicon-based MEMS devices for sensing applications. Although the use of commercial photoresists as structural material in polymer MEMS has been widely reported, the integration of functional polymer materials as electromechanical transducers has not yet received the same amount of interest. In this context, we report on the design and fabrication of different electromechanical schemes based on polymeric materials ensuring different transduction functions. Piezoresistive transduction made of carbon nanotube-based nanocomposites with a gauge factor of 200 was embedded within U-shaped polymeric cantilevers operating either in static or dynamic modes. Flexible resonators with integrated piezoelectric transduction were also realized and used as efficient viscosity sensors. Finally, piezoelectric-based organic field effect transistor (OFET) electromechanical transduction exhibiting a record sensitivity of over 600 was integrated into polymer cantilevers and used as highly sensitive strain and humidity sensors. Such advances in integrated electromechanical transduction schemes should favor the development of novel all-polymer MEMS devices for flexible and wearable applications in the future. Full article
(This article belongs to the Special Issue Polymer Based MEMS and Microfabrication)
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