Editorial

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Open AccessEditorial

Special Issue: 15 Years of SU8 as MEMS Material

by Arnaud Bertsch and Philippe Renaud

Micromachines 2015, 6(6), 790-792; https://doi.org/10.3390/mi6060790 - 19 Jun 2015

Cited by 20 | Viewed by 4995

In 1997, the first paper using SU-8 as a material for microfabrication was published [1], demonstrating the interest of this negative photoresist for the near-UV structuration of thick layers and the manufacturing of high aspect-ratio components.[...] Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

Research

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5224 KiB

Open AccessArticle

Novel SU-8/Ionic Liquid Composite for Tribological Coatings and MEMS

by Leili Batooli, Sandra Guadalupe Maldonado, Moshe Judelewicz and Stefano Mischler

Micromachines 2015, 6(5), 611-621; https://doi.org/10.3390/mi6050611 - 19 May 2015

Cited by 10 | Viewed by 6131

Abstract

Tribology of SU-8 polymer is increasingly relevant due to bursting use of this material in a variety of applications. This study is directed towards introduction and investigation of a novel self-lubricating composite of an ionic liquid (IL) in SU-8. The new material can [...] Read more.

Tribology of SU-8 polymer is increasingly relevant due to bursting use of this material in a variety of applications. This study is directed towards introduction and investigation of a novel self-lubricating composite of an ionic liquid (IL) in SU-8. The new material can be utilized for fabrication of lubricating polymer coating with tunable surface properties or SU8-made elements for microelectromechanical systems (MEMS) with enhanced tribological performance. It is shown that addition of IL drastically alters water affinity of the composite while UV patternability remains unmodified. A lower coefficient of friction and wear has been obtained for two investigated compositions with 4 and 10 wt % ionic liquid. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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4319 KiB

Open AccessArticle

Transferable Integrated Optical SU8 Devices: From Micronic Waveguides to 1D-Nanostructures

by Nolwenn Huby, John Bigeon, Gwennaël Danion, Jean-Luc Duvail, Françis Gouttefangeas, Loïc Joanny and Bruno Bêche

Micromachines 2015, 6(5), 544-553; https://doi.org/10.3390/mi6050544 - 23 Apr 2015

Cited by 5 | Viewed by 5921

Abstract

We report on optical components for integrated optics applications at the micro- and nanoscale. Versatile shapes and dimensions are achievable due to the liquid phase processability of SU8 resist. On the one hand, by adjusting the UV-lithography process, waveguiding structures are patterned and [...] Read more.

We report on optical components for integrated optics applications at the micro- and nanoscale. Versatile shapes and dimensions are achievable due to the liquid phase processability of SU8 resist. On the one hand, by adjusting the UV-lithography process, waveguiding structures are patterned and released from their original substrate. They can be replaced on any other substrate and also immerged in liquid wherein they still show off efficient light confinement. On the other hand, filled and hollow 1D-nanostructures are achievable by the wetting template method. By exploiting the large range of available SU8 viscosities, nanowires of diameter ranging between 50 nm and 240 nm, as well as nanotubes of controllable wall thickness are presented. Optical injection, propagation, and coupling in such nanostructures are relevant for highly integrated devices. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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3745 KiB

Open AccessArticle

Performance of SU-8 Membrane Suitable for Deep X-Ray Grayscale Lithography

by Harutaka Mekaru

Micromachines 2015, 6(2), 252-265; https://doi.org/10.3390/mi6020252 - 09 Feb 2015

Cited by 13 | Viewed by 13150

Abstract

In combination with tapered-trench-etching of Si and SU-8 photoresist, a grayscale mask for deep X-ray lithography was fabricated and passed a 10-times-exposure test. The performance of the X-ray grayscale mask was evaluated using the TERAS synchrotron radiation facility at the National Institute of [...] Read more.

In combination with tapered-trench-etching of Si and SU-8 photoresist, a grayscale mask for deep X-ray lithography was fabricated and passed a 10-times-exposure test. The performance of the X-ray grayscale mask was evaluated using the TERAS synchrotron radiation facility at the National Institute of Advanced Industrial Science and Technology (AIST). Although the SU-8 before photo-curing has been evaluated as a negative-tone photoresist for ultraviolet (UV) and X-ray lithographies, the characteristic of the SU-8 after photo-curing has not been investigated. A polymethyl methacrylate (PMMA) sheet was irradiated by a synchrotron radiation through an X-ray mask, and relationships between the dose energy and exposure depth, and between the dose energy and dimensional transition, were investigated. Using such a technique, the shape of a 26-μm-high Si absorber was transformed into the shape of a PMMA microneedle with a height of 76 μm, and done with a high contrast. Although during the fabrication process of the X-ray mask a 100-μm-pattern-pitch (by design) was enlarged to 120 μm. However, with an increase in an integrated dose energy this number decreased to 99 μm. These results show that the X-ray grayscale mask has many practical applications. In this paper, the author reports on the evaluation results of SU-8 when used as a membrane material for an X-ray mask. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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2053 KiB

Open AccessArticle

SU-8 Photolithography as a Toolbox for Carbon MEMS

by Rodrigo Martinez-Duarte

Micromachines 2014, 5(3), 766-782; https://doi.org/10.3390/mi5030766 - 22 Sep 2014

Cited by 63 | Viewed by 13513

Abstract

The use of SU-8 as precursor for glass-like carbon, or glassy carbon, is presented here. SU-8 carbonizes when subject to high temperature under inert atmosphere. Although epoxy-based precursors can be patterned in a variety of ways, photolithography is chosen due to its resolution [...] Read more.

The use of SU-8 as precursor for glass-like carbon, or glassy carbon, is presented here. SU-8 carbonizes when subject to high temperature under inert atmosphere. Although epoxy-based precursors can be patterned in a variety of ways, photolithography is chosen due to its resolution and reproducibility. Here, a number of improvements to traditional photolithography are introduced to increase the versatility of the process. The shrinkage of SU-8 during carbonization is then detailed as one of the guidelines necessary to design carbon patterns. A couple of applications—(1) carbon-electrode dielectrophoresis for bioparticle manipulation; and (2) the use of carbon structures as micro-molds are also presented. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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Optimized SU-8 Processing for Low-Cost Microstructures Fabrication without Cleanroom Facilities

by Vânia C. Pinto, Paulo J. Sousa, Vanessa F. Cardoso and Graça Minas

Micromachines 2014, 5(3), 738-755; https://doi.org/10.3390/mi5030738 - 22 Sep 2014

Cited by 96 | Viewed by 10107

Abstract

The study and optimization of epoxy-based negative photoresist (SU-8) microstructures through a low-cost process and without the need for cleanroom facility is presented in this paper. It is demonstrated that the Ultraviolet Rays (UV) exposure equipment, commonly used in the Printed Circuit Board [...] Read more.

The study and optimization of epoxy-based negative photoresist (SU-8) microstructures through a low-cost process and without the need for cleanroom facility is presented in this paper. It is demonstrated that the Ultraviolet Rays (UV) exposure equipment, commonly used in the Printed Circuit Board (PCB) industry, can replace the more expensive and less available equipment, as the Mask Aligner that has been used in the last 15 years for SU-8 patterning. Moreover, high transparency masks, printed in a photomask, are used, instead of expensive chromium masks. The fabrication of well-defined SU-8 microstructures with aspect ratios more than 20 is successfully demonstrated with those facilities. The viability of using the gray-scale technology in the photomasks for the fabrication of 3D microstructures is also reported. Moreover, SU-8 microstructures for different applications are shown throughout the paper. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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3832 KiB

Open AccessArticle

Inkjet Printing of High Aspect Ratio Superparamagnetic SU-8 Microstructures with Preferential Magnetic Directions

by Loïc Jacot-Descombes, Maurizio R. Gullo, Victor J. Cadarso, Massimo Mastrangeli, Olgaç Ergeneman, Christian Peters, Philipe Fatio, Mouhamad A. Freidy, Christofer Hierold, Bradley J. Nelson and Jürgen Brugger

Micromachines 2014, 5(3), 583-593; https://doi.org/10.3390/mi5030583 - 25 Aug 2014

Cited by 16 | Viewed by 8358

Abstract

Structuring SU-8 based superparamagnetic polymer composite (SPMPC) containing Fe₃O₄ nanoparticles by photolithography is limited in thickness due to light absorption by the nanoparticles. Hence, obtaining thicker structures requires alternative processing techniques. This paper presents a method based on inkjet printing [...] Read more.

Structuring SU-8 based superparamagnetic polymer composite (SPMPC) containing Fe₃O₄ nanoparticles by photolithography is limited in thickness due to light absorption by the nanoparticles. Hence, obtaining thicker structures requires alternative processing techniques. This paper presents a method based on inkjet printing and thermal curing for the fabrication of much thicker hemispherical microstructures of SPMPC. The microstructures are fabricated by inkjet printing the nanoparticle-doped SU-8 onto flat substrates functionalized to reduce the surface energy and thus the wetting. The thickness and the aspect ratio of the printed structures are further increased by printing the composite onto substrates with confinement pedestals. Fully crosslinked microstructures with a thickness up to 88.8 μm and edge angle of 112° ± 4° are obtained. Manipulation of the microstructures by an external field is enabled by creating lines of densely aggregated nanoparticles inside the composite. To this end, the printed microstructures are placed within an external magnetic field directly before crosslinking inducing the aggregation of dense Fe₃O₄ nanoparticle lines with in-plane and out-of-plane directions. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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Implementation of Synchronous Micromotor in Developing Integrated Microfluidic Systems

by Ala'aldeen Al-Halhouli, Stefanie Demming, Andreas Waldschik and Stephanus Büttgenbach

Micromachines 2014, 5(3), 442-456; https://doi.org/10.3390/mi5030442 - 18 Jul 2014

Cited by 19 | Viewed by 8249

Abstract

This paper introduces the synchronous micromotor concept and presents new investigations on its application as an integrated driving mechanism in microfluidic systems. A spiral channel viscous micropump and a microstirrer are considered and tested as examples to verify the concept. The fabrication technology [...] Read more.

This paper introduces the synchronous micromotor concept and presents new investigations on its application as an integrated driving mechanism in microfluidic systems. A spiral channel viscous micropump and a microstirrer are considered and tested as examples to verify the concept. The fabrication technology of such integrated systems is based on UV depth lithography, electroplating and soft lithography. The synchronous micromotor consists of a stator including double layer coils, and a rotor disk containing alternate permanent magnets. The coils are distributed evenly around the stator and arranged in three phases. The phases are excited by sinusoidal currents with a corresponding phase shift resulting in a rotating magnetic field. Regarding the spiral channel viscous micropump, a spiral disk was fixed onto the rotor disk and run at different rotational speeds. Tests showed very promising results, with a flow rate up to 1023 µL·min⁻¹ at a motor rotational speed of 4500 rpm. Furthermore, for the application of a microstirred-tank bioreactor, the rotor disk design was modified to work as a stirrer. The performance of the developed microbioreactor was tested over a time period of approximately 10 h under constant stirring. Tests demonstrated the successful cultivation of S. cerevisiae through the integration of the microstirrer in a microbioreactor system. These systems prove that synchronous micromotors are well suited to serve as integrated driving mechanisms of active microfluidic components. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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Open AccessArticle

SU-8 Composite Based “Lube-tape” for a Wide Range of Tribological Applications

by Prabakaran Saravanan, Nalam Satyanarayana and Sujeet K. Sinha

Micromachines 2014, 5(2), 263-274; https://doi.org/10.3390/mi5020263 - 19 May 2014

Cited by 1 | Viewed by 6540

Abstract

In a previous work, we have developed a perflouropolyether (PFPE) lubricant droplet-filled SU-8 composite which promotes bonding between the molecules of SU-8 and PFPE and provides excellent boundary lubrication. The SU-8 + PFPE composite has enhanced the wear durability of SU-8 by more [...] Read more.

In a previous work, we have developed a perflouropolyether (PFPE) lubricant droplet-filled SU-8 composite which promotes bonding between the molecules of SU-8 and PFPE and provides excellent boundary lubrication. The SU-8 + PFPE composite has enhanced the wear durability of SU-8 by more than four orders of magnitude. In this work, the same SU-8 + PFPE composite was used to fabricate a stand-alone laminate film called “Lube-tape”. It has integrated two layers of approximately 90 microns thickness each; the top layer is made of SU-8 + PFPE composite and the bottom layer of pristine SU-8. Thus, a single tape can have drastically contrasting high friction and low friction properties on its two surfaces. The composite side has the initial coefficient of friction ~7 times lower and the wear life more than four orders of magnitude than those of the pristine SU-8 side. This lube tape can be used on any load bearing surface to improve the tribological performance by simply pasting the pristine SU-8 side onto the substrate. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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Open AccessArticle

Biomimetic Pieris rapae’s Nanostructure and Its Use as a Simple Sucrose Sensor

by David Bonzon, Rodrigo Martinez-Duarte, Philippe Renaud and Marc Madou

Micromachines 2014, 5(2), 216-227; https://doi.org/10.3390/mi5020216 - 23 Apr 2014

Cited by 2 | Viewed by 7214

Abstract

Biomimetics often provides efficient ways to create a product incorporating novel properties. Here we present the replication of the Pieris rapae butterfly optical structure. This butterfly has white wings with black spots. The white coloration is produced by light scattering on pterin beads [...] Read more.

Biomimetics often provides efficient ways to create a product incorporating novel properties. Here we present the replication of the Pieris rapae butterfly optical structure. This butterfly has white wings with black spots. The white coloration is produced by light scattering on pterin beads ranging from 100 to 500 nm whereas black spots correspond to areas without pterin beads, thus revealing a highly pigmented layer underneath. In order to mimic the butterfly wing structure, we deposited SU-8 beads produced by electrospraying on a black absorbing layer made of black SU-8. We thereby replicated the optical effect observed on Pieris rapae. Additional experiments showed that the white coloration replication is a structural color. Finally, we further demonstrate that these optical engineered surfaces can be used for sucrose sensing in the range of 1 g/L to 250 g/L. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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Review

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Innovative SU-8 Lithography Techniques and Their Applications

by Jeong Bong Lee, Kyung-Hak Choi and Koangki Yoo

Micromachines 2015, 6(1), 1-18; https://doi.org/10.3390/mi6010001 - 23 Dec 2014

Cited by 61 | Viewed by 19407

Abstract

SU-8 has been widely used in a variety of applications for creating structures in micro-scale as well as sub-micron scales for more than 15 years. One of the most common structures made of SU-8 is tall (up to millimeters) high-aspect-ratio (up to 100:1) [...] Read more.

SU-8 has been widely used in a variety of applications for creating structures in micro-scale as well as sub-micron scales for more than 15 years. One of the most common structures made of SU-8 is tall (up to millimeters) high-aspect-ratio (up to 100:1) 3D microstructure, which is far better than that made of any other photoresists. There has been a great deal of efforts in developing innovative unconventional lithography techniques to fully utilize the thick high aspect ratio nature of the SU-8 photoresist. Those unconventional lithography techniques include inclined ultraviolet (UV) exposure, back-side UV exposure, drawing lithography, and moving-mask UV lithography. In addition, since SU-8 is a negative-tone photoresist, it has been a popular choice of material for multiple-photon interference lithography for the periodic structure in scales down to deep sub-microns such as photonic crystals. These innovative lithography techniques for SU-8 have led to a lot of unprecedented capabilities for creating unique micro- and nano-structures. This paper reviews such innovative lithography techniques developed in the past 15 years or so. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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Open AccessReview

SU-8 as a Material for Microfabricated Particle Physics Detectors

by Pietro Maoddi, Alessandro Mapelli, Sebastien Jiguet and Philippe Renaud

Micromachines 2014, 5(3), 594-606; https://doi.org/10.3390/mi5030594 - 26 Aug 2014

Cited by 4 | Viewed by 7014

Abstract

Several recent detector technologies developed for particle physics applications are based on microfabricated structures. Detectors built with this approach generally exhibit the overall best performance in terms of spatial and time resolution. Many properties of the SU-8 photoepoxy make it suitable for the [...] Read more.

Several recent detector technologies developed for particle physics applications are based on microfabricated structures. Detectors built with this approach generally exhibit the overall best performance in terms of spatial and time resolution. Many properties of the SU-8 photoepoxy make it suitable for the manufacturing of microstructured particle detectors. This article aims to review some emerging detector technologies making use of SU-8 microstructuring, namely micropattern gaseous detectors and microfluidic scintillation detectors. The general working principle and main process steps for the fabrication of each device are reported, with a focus on the advantages brought to the device functionality by the use of SU-8. A novel process based on multiple bonding steps for the fabrication of thin multilayer microfluidic scintillation detectors developed by the authors is presented. Finally, a brief overview of the applications for the discussed devices is given. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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UV-LIGA: From Development to Commercialization

by Grégoire Genolet and Hubert Lorenz

Micromachines 2014, 5(3), 486-495; https://doi.org/10.3390/mi5030486 - 23 Jul 2014

Cited by 25 | Viewed by 9860

Abstract

A major breakthrough in UV-LIGA (Lithographie, Galvanoformung and Abformung) started with the use of epoxy-based EPON^® SU-8 photoresist in the mid-1990s. Using this photoresist has enabled the fabrication of tall and high aspect ratio structures without the use of a very expensive [...] Read more.

A major breakthrough in UV-LIGA (Lithographie, Galvanoformung and Abformung) started with the use of epoxy-based EPON^® SU-8 photoresist in the mid-1990s. Using this photoresist has enabled the fabrication of tall and high aspect ratio structures without the use of a very expensive synchrotron source needed to expose the photoresist layer in X-ray LIGA. SU-8 photoresist appeared to be well-suited for LIGA templates, but also as a permanent material. Based on UV-LIGA and SU-8, Mimotec SA has developed processes to manufacture mold inserts and metallic components for various market fields. From one to three-level parts, from Ni to other materials, from simple to complicated parts with integrated functionalities, UV-LIGA has established itself as a manufacturing technology of importance for prototyping, as well as for mass-fabrication. This paper reviews some of the developments that led to commercial success in this field. Full article

(This article belongs to the Special Issue 15 Years of SU8 as MEMS Material)

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