Special Issue "Polymeric Microsystems"

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

Deadline for manuscript submissions: closed (25 May 2016)

Special Issue Editor

Guest Editor
Prof. Dr. Andreas Richter

Polymeric Microsystems, Technische Universität Dresden, Dresden 01062, Germany
Website | E-Mail
Phone: +49-351-463-36336
Fax: +49-351-463-37021
Interests: microsystems; system integration; microfluidics; chemical sensors and sensor systems; imaging systems; energy harvesting; actuator systems; intrinsically active polymers; chemical information processing

Special Issue Information

Dear Colleagues,

Polymeric microsystems are much more than a cheap alternative to common silicon-based microsystems. In the fields of optics, display technologies, multifunctional electronics, sensors, actuators, energy harvesting, and microfluidics, they offer features which significantly exceed the possibilities of silicon-based systems.

This Special Issue highlights the potential of polymeric microsystems in various fields of applications. It includes:

(i) fabrication technologies for polymeric microsystems,
(ii) concepts of active polymeric components, modules and complete systems,
(iii) modelling and simulation of polymeric material behaviors in components and chips, as well as
(iv) exemplary applications.

Of particular interest are, on the one hand, intrinsically active polymers, such as piezo polymers, shape memory polymers, stimuli-responsive hydrogels and conductive polymers, and, on the other hand, electroactive polymers, such as dielectric elastomers.

Prof. Dr. Andreas Richter
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.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind 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). 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

  • technologies for polymeric microsystems
  • intrinsically active polymers
  • stimuli responsive hydrogels
  • shape memory polymers
  • piezo polymers
  • conductive polymers
  • electroactive polymers
  • sensors, actuators
  • optical modulators
  • multi modal modulators

Published Papers (6 papers)

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Research

Open AccessArticle Microfluidic 3D Helix Mixers
Micromachines 2016, 7(10), 189; doi:10.3390/mi7100189
Received: 12 July 2016 / Revised: 30 August 2016 / Accepted: 6 October 2016 / Published: 17 October 2016
Cited by 4 | PDF Full-text (6960 KB) | HTML Full-text | XML Full-text
Abstract
Polymeric microfluidic systems are well suited for miniaturized devices with complex functionality, and rapid prototyping methods for 3D microfluidic structures are increasingly used. Mixing at the microscale and performing chemical reactions at the microscale are important applications of such systems and we therefore
[...] Read more.
Polymeric microfluidic systems are well suited for miniaturized devices with complex functionality, and rapid prototyping methods for 3D microfluidic structures are increasingly used. Mixing at the microscale and performing chemical reactions at the microscale are important applications of such systems and we therefore explored feasibility, mixing characteristics and the ability to control a chemical reaction in helical 3D channels produced by the emerging thread template method. Mixing at the microscale is challenging because channel size reduction for improving solute diffusion comes at the price of a reduced Reynolds number that induces a strictly laminar flow regime and abolishes turbulence that would be desired for improved mixing. Microfluidic 3D helix mixers were rapidly prototyped in polydimethylsiloxane (PDMS) using low-surface energy polymeric threads, twisted to form 2-channel and 3-channel helices. Structure and flow characteristics were assessed experimentally by microscopy, hydraulic measurements and chromogenic reaction, and were modeled by computational fluid dynamics. We found that helical 3D microfluidic systems produced by thread templating allow rapid prototyping, can be used for mixing and for controlled chemical reaction with two or three reaction partners at the microscale. Compared to the conventional T-shaped microfluidic system used as a control device, enhanced mixing and faster chemical reaction was found to occur due to the combination of diffusive mixing in small channels and flow folding due to the 3D helix shape. Thus, microfluidic 3D helix mixers can be rapidly prototyped using the thread template method and are an attractive and competitive method for fluid mixing and chemical reactions at the microscale. Full article
(This article belongs to the Special Issue Polymeric Microsystems)
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Open AccessArticle Full Polymer Dielectric Elastomeric Actuators (DEA) Functionalised with Carbon Nanotubes and High-K Ceramics
Micromachines 2016, 7(10), 172; doi:10.3390/mi7100172
Received: 6 July 2016 / Revised: 11 August 2016 / Accepted: 5 September 2016 / Published: 23 September 2016
Cited by 2 | PDF Full-text (6112 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Dielectric elastomer actuators (DEA) are special devices which have a simple working and construction principle and outstanding actuation properties. The DEAs consist of a combination of different materials for the dielectric and electrode layers. The combination of these layers causes incompatibilities in their
[...] Read more.
Dielectric elastomer actuators (DEA) are special devices which have a simple working and construction principle and outstanding actuation properties. The DEAs consist of a combination of different materials for the dielectric and electrode layers. The combination of these layers causes incompatibilities in their interconnections. Dramatic differences in the mechanical properties and bad adhesion of the layers are the principal causes for the reduction of the actuation displacement and strong reduction of lifetime. Common DEAs achieve actuation displacements of 2% and a durability of some million cycles. The following investigations represent a new approach to solving the problems of common systems. The investigated DEA consists of only one basic raw polymer, which was modified according to the required demands of each layer. The basic raw polymer was modified with single-walled carbon nanotubes or high-k ceramics, for example, lead magnesium niobate-lead titanate. The development of the full polymer DEA comprised the development of materials and technologies to realise a reproducible layer composition. It was proven that the full polymer actuator worked according to the theoretical rules. The investigated system achieved actuation displacements above 20% regarding thickness, outstanding interconnections at each layer without any failures, and durability above 3 million cycles without any indication of an impending malfunction. Full article
(This article belongs to the Special Issue Polymeric Microsystems)
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Open AccessFeature PaperArticle Ionoprinted Multi-Responsive Hydrogel Actuators
Micromachines 2016, 7(6), 98; doi:10.3390/mi7060098
Received: 27 April 2016 / Revised: 16 May 2016 / Accepted: 17 May 2016 / Published: 26 May 2016
Cited by 7 | PDF Full-text (12817 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
We report multi-responsive and double-folding bilayer hydrogel sheet actuators, whose directional bending response is tuned by modulating the solvent quality and temperature and where locally crosslinked regions, induced by ionoprinting, enable the actuators to invert their bending axis. The sheets are made multi-responsive
[...] Read more.
We report multi-responsive and double-folding bilayer hydrogel sheet actuators, whose directional bending response is tuned by modulating the solvent quality and temperature and where locally crosslinked regions, induced by ionoprinting, enable the actuators to invert their bending axis. The sheets are made multi-responsive by combining two stimuli responsive gels that incur opposing and complementary swelling and shrinking responses to the same stimulus. The lower critical solution temperature (LCST) can be tuned to specific temperatures depending on the EtOH concentration, enabling the actuators to change direction isothermally. Higher EtOH concentrations cause upper critical solution temperature (UCST) behavior in the poly(N-isopropylacrylamide) (pNIPAAm) gel networks, which can induce an amplifying effect during bilayer bending. External ionoprints reliably and repeatedly invert the gel bilayer bending axis between water and EtOH. Placing the ionoprint at the gel/gel interface can lead to opposite shape conformations, but with no clear trend in the bending behavior. We hypothesize that this is due to the ionoprint passing through the neutral axis of the bilayer during shrinking in hot water. Finally, we demonstrate the ability of the actuators to achieve shapes unique to the specific external conditions towards developing more responsive and adaptive soft actuator devices. Full article
(This article belongs to the Special Issue Polymeric Microsystems)
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Open AccessArticle Characterizing the Deformation of the Polydimethylsiloxane (PDMS) Membrane for Microfluidic System through Image Processing
Micromachines 2016, 7(5), 92; doi:10.3390/mi7050092
Received: 1 March 2016 / Revised: 11 April 2016 / Accepted: 3 May 2016 / Published: 16 May 2016
Cited by 1 | PDF Full-text (13471 KB) | HTML Full-text | XML Full-text
Abstract
Polydimethylsiloxane (PDMS) membranes have been widely used in the microfluidic community to achieve various functions such as control, sensing, filter, etc. In this paper, an experimental process was proposed to directly characterize the deformation of the on-chip PDMS membrane at large deformation based
[...] Read more.
Polydimethylsiloxane (PDMS) membranes have been widely used in the microfluidic community to achieve various functions such as control, sensing, filter, etc. In this paper, an experimental process was proposed to directly characterize the deformation of the on-chip PDMS membrane at large deformation based on the image processing method. High precision pressures were applied on the surface of the PDMS membrane with fixed edges and a series deformation of the PDMS membrane were captured by the imaging system. The Chan and Vese (CV) level set method was applied to segment the images of the deformed membrane. The volumes wrapped by the deformed membranes were obtained, and pressure-volumes relationships of the PDMS membranes with different geometry parameters were also calculated. Then the membrane capacitance can be derived by differentiating the curve of pressure-volumes. In addition, the theoretical estimation of the capacitance of the PDMS membrane at large deformation was also obtained through finite element simulation (FEM), which was in good agreement with the experimental results. These results are expected to be significant for designing and on-chip measuring of such PDMS membrane based microfluidic components in our future work. Full article
(This article belongs to the Special Issue Polymeric Microsystems)
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Open AccessArticle Micro-Shaping of Nanopatterned Surfaces by Electron Beam Irradiation
Micromachines 2016, 7(4), 66; doi:10.3390/mi7040066
Received: 21 February 2016 / Revised: 30 March 2016 / Accepted: 8 April 2016 / Published: 13 April 2016
Cited by 1 | PDF Full-text (3491 KB) | HTML Full-text | XML Full-text
Abstract
We show that planar nanopatterned thin films on standard polycarbonate (PC) compact discs (CD) can be micro-shaped in a non-contact manner via direct e-beam exposure. The shape of the film can be controlled by proper selection of the e-beam parameters. As an example
[...] Read more.
We show that planar nanopatterned thin films on standard polycarbonate (PC) compact discs (CD) can be micro-shaped in a non-contact manner via direct e-beam exposure. The shape of the film can be controlled by proper selection of the e-beam parameters. As an example of application, we demonstrate a two-dimensional (2D) array of micro-lenses/reservoirs conformally covered by an Al 2D nanohole array (NHA) film on a PC CD substrate. It is also shown that such a curvilinear Al NHA layer can be easily transferred onto a flexible polymeric support. The presented technique provides a new tool for creating lab-on-CD architectures and developing multifunctional (flexible) non-planar nanostructured films and surfaces. Full article
(This article belongs to the Special Issue Polymeric Microsystems)
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Open AccessArticle A Simple and Reliable PDMS and SU-8 Irreversible Bonding Method and Its Application on a Microfluidic-MEA Device for Neuroscience Research
Micromachines 2015, 6(12), 1923-1934; doi:10.3390/mi6121465
Received: 27 October 2015 / Revised: 18 November 2015 / Accepted: 1 December 2015 / Published: 7 December 2015
Cited by 6 | PDF Full-text (2622 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Polydimethylsiloxane (PDMS) and SU-8 are currently two very commonly used polymeric materials in the microfluidics field for biological applications. However; there is a pressing need to find a simple, reliable, irreversible bonding method between these two materials for their combined use in innovative
[...] Read more.
Polydimethylsiloxane (PDMS) and SU-8 are currently two very commonly used polymeric materials in the microfluidics field for biological applications. However; there is a pressing need to find a simple, reliable, irreversible bonding method between these two materials for their combined use in innovative integrated microsystems. In this paper, we attempt to investigate the aminosilane-mediated irreversible bonding method for PDMS and SU-8 with X-Ray Photoelectron Spectroscopy (XPS) surface analysis and bonding strength tests. Additionally, the selected bonding method was applied in fabricating a microelectrode array (MEA) device, including microfluidic features, which allows electrophysiological observations on compartmentalized neuronal cultures. As there is a growing trend towards microfluidic devices for neuroscience research, this type of integrated microdevice, which can observe functional alterations on compartmentalized neuronal culture, can potentially be used for neurodegenerative disease research and pharmaceutical development. Full article
(This article belongs to the Special Issue Polymeric Microsystems)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Ionoprinted Multi-Responsive Hydrogel Bilayers
Authors: Daniel Morales, Igor Podolsky, Russell Mailen, Michael D. Dickey,* Orlin D. Velev*
Abstract: There has been increasing interest and progress in engineering soft, shape-transforming materials which can mimic the sensing and response mechanisms found in nature. Hydrogels have become a model material for exploring stimuli-responsive behaviors in solvents. This is due to their ability to incur large volume changes in response to a multitude of external stimuli. The mechanical properties of hydrogels can be modulated by functionalizing the gel with gradient structures to achieve controlled actuation in response to the external environment. These gradient structures most often are introduced by designing bilayer gel systems, particle or interpenetrating polymer hydrogel composites and regions of varying crosslink density both through the gel depth or in-plane. The differential swelling along or across the gel systems leads to a buildup of internal stresses resulting in reversible, 3D shape transformations. Such biocompatible, adaptive materials are being applied to a broad range of applications including biomaterials, soft robotics, drug delivery, microfluidics and sensing. Several challenges need to be addressed to enable their ubiquitous use as functional, soft devices such as improving their slow response times and weak mechanical properties. Furthermore, previously explored actuation mechanisms generally result in an “on” or “off” state, determined by the magnitude of the applied stimulus. Our desire is to begin to develop synthetic systems which reconfigure into 3D structures that are uniquely and proportionally responsive to a specific set of external conditions, towards developing “intelligent” soft materials. Previous groups developed multi-responsive gels by incorporating separate networks sensitive to different stimuli into one gel composite, incorporating bi-axial stresses with crosslinking gradients or by incorporating modular gel building blocks into 3D geometries. These gel systems have large response times (~ hrs) and require photolithographic processing techniques. Here, we have developed multi-responsive gel bilayer sheets by combining thermoresponsive poly (N-isopropylacrylamide) (pNIPAAm) with superabsorbent sodium poly(sodium acrylate) (pNaAc) gels. The actuators can be created rapidly and are functionalized with reversible, locally crosslinked regions. The bending can be tuned to reverse direction isothermally by changing the solvent quality or by changing the temperature at a fixed concentration. We achieve this by making use of the LCST (lower critical solution temperature) and UCST (upper critical solution temperature) transitions that pNIPAAm can incur in the presence of the appropriate cononsolvent. The bilayers can be programmed to invert their bending axis by utilizing an ionic crosslinking technique, ionoprinting, developed previously in our group. Ionoprinting renders the bilayer sheets reprogrammable due to the ability to erase the ionic crosslinks. We demonstrate the use of these simple fabrication techniques to produce gel actuators which can transform into unique shapes with a fast response time.

Title: 3D Printed Microfluidic E-Tongue in Soil Sample Analysis
Author: Toni Riul
Abstract: 3D printing is transforming ideas in numerous applications, driving new directions in microfluidics. It is an emerging technology offering a fast, cost-effective way to produce complex structures with high resolution to assembly integrated devices. The development of devices with improved features can be accelerated by combining forefront tools for rapid prototyping and simplification of the fabrication process. Here, the layer-by-layer technique was combined with a 3D printed microfluidic platform as a new strategy to form an electronic tongue system. Transparent microchannels made with polylactic acid (PLA), a cheap alternative material to overcome the PDMS realms, were built in a home-made fused deposition modeling (FDM) 3D printer. Interdigitated electrodes could be easily inserted and sealed in one-step process using the FDM technology to form individual sensing units. As a proof-of-concept, Principal Component Analysis was used to correlate soil samples analysed by a 3D-printed e-tongue device, paving the way for future developments in the agro-food sector.

Title: Microfluidic Circular Channel Helices
Author: Georgette Salieb-Beugelaar

Title: Flexible Production Systems for Diagnostic Cartridges
Authors: Dominique Kosse, Daniel Baumann and Felix von Stetten

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