Micromachines

23 pages, 1201 KiB

Open AccessArticle

Surface Tension Flows inside Surfactant-Added Poly(dimethylsiloxane) Microstructures with Velocity-Dependent Contact Angles

by Jyh Jian Chen^1,*

, Shih Chuan Liao¹, Mao Hsun Liu², Jenn Der Lin³, Tsung Sheng Sheu⁴ and Ming Miao, Jr.¹

¹ Department of Biomechatronics Engineering, National Pingtung University of Science and Technology, 1, Shuefu Road, Neipu, Pingtung 91201, Taiwan

² Department of Mechanical Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan

³ Department of Power Mechanical Engineering, National Formosa University, 64, Wunhua Road, Huwei, Yunlin 63201, Taiwan

⁴ Department of Mechanical Engineering, Chinese Military Academy, 1, Weiwu Road, Fengshan, Kaohsiung 83059, Taiwan

Micromachines 2014, 5(2), 116-138; https://doi.org/10.3390/mi5020116 - 25 Mar 2014

Cited by 4 | Viewed by 8645

Abstract

Filling of liquid samples is realized in a microfluidic device with applications including analytical systems, biomedical devices, and systems for fundamental research. The filling of a disk-shaped polydimethylsiloxane (PDMS) microchamber by liquid is analyzed with reference to microstructures with inlets and outlets. The [...] Read more.

Filling of liquid samples is realized in a microfluidic device with applications including analytical systems, biomedical devices, and systems for fundamental research. The filling of a disk-shaped polydimethylsiloxane (PDMS) microchamber by liquid is analyzed with reference to microstructures with inlets and outlets. The microstructures are fabricated using a PDMS molding process with an SU-8 mold. During the filling, the motion of the gas-liquid interface is determined by the competition among inertia, adhesion, and surface tension. A single ramp model with velocity-dependent contact angles is implemented for the accurate calculation of surface tension forces in a three-dimensional volume-of-fluid based model. The effects of the parameters of this functional form are investigated. The influences of non-dimensional parameters, such as the Reynolds number and the Weber number, both determined by the inlet velocity, on the flow characteristics are also examined. An oxygen-plasma-treated PDMS substrate is utilized, and the microstructure is modified to be hydrophilic. Flow experiments are conducted into both hydrophilic and hydrophobic PDMS microstructures. Under a hydrophobic wall condition, numerical simulations with imposed boundary conditions of static and dynamic contact angles can successfully predict the moving of the meniscus compared with experimental measurements. However, for a hydrophilic wall, accurate agreement between numerical and experimental results is obvious as the dynamic contact angles were implemented. Full article

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15 pages, 725 KiB

Open AccessArticle

Gravitational Field-Flow Fractionation Devices Fabricated via a Hot Embossing/Thermal Bonding Method

by Kaijun Yang

School of Mechanical & Electronical Engineering, Lanzhou University of Technology, Lanzhou 730050, China

Micromachines 2014, 5(2), 139-153; https://doi.org/10.3390/mi5020139 - 3 Apr 2014

Cited by 1 | Viewed by 6581

Abstract

A novel hot embossing/low temperature ethanol solvent bonding method for the fabrication of polymethylmethacrylate (PMMA) field flow fractionation devices has been developed. The separation channel on a PMMA substrate was generated by a hot embossing process without vacuum. Special temperature-pressure profiles were used [...] Read more.

A novel hot embossing/low temperature ethanol solvent bonding method for the fabrication of polymethylmethacrylate (PMMA) field flow fractionation devices has been developed. The separation channel on a PMMA substrate was generated by a hot embossing process without vacuum. Special temperature-pressure profiles were used to analyze the influence of the hot embossing parameters. After the hot embossing process, ethanol solvent bonding was used to seal the separation channel on the PMMA substrate. The experimental results show that the bonding strength with ethanol solvent bonding at 35 °C (aspect ratio (depth/width): 0.043) is 3.05 MPa, and the deformation percentage is very low (0.54%). A burst pressure test indicated that the as-prepared PMMA gravitational field flow fractionation device has a very high burst pressure. Furthermore, the higher resolution of the as-prepared PMMA gravitational field flow fractionation device in the separation of wheat and starch particles shows that the hot embossing/low temperature ethanol solvent bonding technique will have potential commercial value. Full article

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4 pages, 90 KiB

Open AccessEditorial

Micro/Nanofluidic Devices for Single Cell Analysis

by Tuhin Subhra Santra¹

and Fan Gang Tseng^1,2,3,*

¹ Institute of Nano Engineering and Microsystems, National Tsing Hua University, Kuang Fu Road, No. 101, Section 2, Hsinchu 30013, Taiwan

² Department of Engineering and System Science, National Tsing Hua University, Kuang Fu Road, No. 101, Section 2, Hsinchu 30013, Taiwan

³ Division of Mechanics, Research Center for Applied Sciences, Academia Sinica, Nankang, 11574, Taipei, Taiwan

Micromachines 2014, 5(2), 154-157; https://doi.org/10.3390/mi5020154 - 3 Apr 2014

Cited by 24 | Viewed by 6635

Abstract

The Special Issue of Micromachines entitled “Micro/Nanofluidic Devices for Single Cell Analysis” covers recent advancements regarding the analysis of single cells by different microfluidic approaches. To understand cell to cell behavior with their organelles and their intracellular biochemical effect, single cell analysis (SCA) [...] Read more.

The Special Issue of Micromachines entitled “Micro/Nanofluidic Devices for Single Cell Analysis” covers recent advancements regarding the analysis of single cells by different microfluidic approaches. To understand cell to cell behavior with their organelles and their intracellular biochemical effect, single cell analysis (SCA) can provide much more detailed information from small groups of cells or even single cells, compared to conventional approaches, which only provide ensemble-average information of millions of cells together. Earlier reviews provided single cell analysis using different approaches [1–3]. The author demonstrates invasive and noninvasive with time and non-time resolved SCA [1]; whereas some other literature provided destructive (with dyes, DNA, RNA, proteins and amino acids) and nondestructive (electroporation, impedance measurement and fluorescence based methods) cellular content analysis using microfluidic devices [3]. Further literature also suggest that single cell analysis is possible with capillary electrophoresis (CE) combined with a detection method such as electrochemical detection (ED), laser induced fluorescence (LIF) detection and mass spectrometry (MS) [4,5]. [...] Full article

(This article belongs to the Special Issue Micro/Nanofluidic Devices for Single Cell Analysis)

13 pages, 4645 KiB

Open AccessArticle

A Semi-Closed Device for Chromosome Spreading for Cytogenetic Analysis

by Dorota Kwasny¹, Olga Mednova¹, Indumathi Vedarethinam², Maria Dimaki¹, Asli Silahtaroglu³, Zeynep Tümer⁴

, Kristoffer Almdal¹ and Winnie E. Svendsen^1,*

¹ Department of Micro- and Nanotechnology, Technical University of Denmark, Orsteds Plads, 2800 Kgs. Lyngby 2800, Denmark

² Center for Molecular Biology 'Severo Ochoa', UAM campus Cantoblano, Madrid 28049, Spain

³ Faculty of Health Sciences, Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen 2200, Denmark

⁴ Applied Human Molecular Genetics, Kennedy Center, Copenhagen University Hospital, Rigshospitalet, Glostrup 2600, Denmark

Micromachines 2014, 5(2), 158-170; https://doi.org/10.3390/mi5020158 - 3 Apr 2014

Cited by 4 | Viewed by 7066

Abstract

Metaphase chromosome spreading is the most crucial step required for successful karyotyping and FISH analysis. These two techniques are routinely used in cytogenetics to assess the chromosome abnormalities. The spreading process has been studied for years but it is still considered an art [...] Read more.

Metaphase chromosome spreading is the most crucial step required for successful karyotyping and FISH analysis. These two techniques are routinely used in cytogenetics to assess the chromosome abnormalities. The spreading process has been studied for years but it is still considered an art more than a science. The chromosome spreading greatly depends on the environmental conditions such as humidity and temperature, which govern the evaporation of fixative, in which the cells are suspended. The spreading is normally performed manually in ambient conditions on glass slides, which are hydrophilic, and thus allow for better quality spreads. Further cytogenetic analysis depends on the quality of the spreads, which is dependent on the skills of the personnel and is thus limited to laboratory settings. Here, we present a semi-closed microfluidic chip for preparation of the metaphase spreads on a glass and a Topasr substrate rendered more hydrophilic by oxygen plasma treatment coupled with photografting. The device consists of a microfluidic chamber with perfusion holes that facilitate the evaporation of fixative and reliable formation of the spreads. The usability of the chromosome spreads formed on the glass and the Topasr slide is tested by performing FISH analysis. Full article

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33 pages, 1366 KiB

Open AccessReview

3-D Micro and Nano Technologies for Improvements in Electrochemical Power Devices

by Sunshine Holmberg^1,*, Alexandra Perebikovsky^2,*, Lawrence Kulinsky¹ and Marc Madou^1,3

¹ Department of Mechanical and Aerospace Engineering, University of California, Irvine, 5200 Engineering Hall, Irvine, CA 92697, USA

² Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697, USA

³ Department of Biomedical Engineering, University of California, Irvine, 5200 Engineering Hall, Irvine, CA 92697, USA

Micromachines 2014, 5(2), 171-203; https://doi.org/10.3390/mi5020171 - 8 Apr 2014

Cited by 40 | Viewed by 17727

Abstract

This review focuses on recent advances in micro- and nano-fabrication techniques and their applications to electrochemical power devices, specifically microfabricated Lithium-ion batteries, enzymatic and microbial fuel cells (biofuel cells), and dye-sensitized solar cells (DSSCs). Although the maturity of these three technologies ranges from [...] Read more.

This review focuses on recent advances in micro- and nano-fabrication techniques and their applications to electrochemical power devices, specifically microfabricated Lithium-ion batteries, enzymatic and microbial fuel cells (biofuel cells), and dye-sensitized solar cells (DSSCs). Although the maturity of these three technologies ranges from market ready (batteries) to fundamental research (biofuel cells) to applied research (DSSCs), advances in MEMS (Micro-Electro-Mechanical Systems) and NEMS (Nano-Electro-Mechanical Systems) techniques, particularly modifications in surface area and surface chemistry, and novel genetic and molecular engineering techniques, significantly improve the electrochemical activity of these technologies across the board. For each of these three categories of power-MEMS devices the review covers: (1) The technical challenges facing the performance and fabrication of electrochemical power devices; (2) Current MEMS and NEMS techniques used to improve efficiency; and (3) Future outlook and suggested improvements of MEMS and NEMS for implementation in electrochemical power devices. Full article

(This article belongs to the Special Issue Power MEMS)

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12 pages, 405 KiB

Open AccessArticle

Raman-Spectroscopy Based Cell Identification on a Microhole Array Chip

by Ute Neugebauer^1,2, Christian Kurz³, Thomas Bocklitz⁴

, Tina Berger⁵, Thomas Velten³, Joachim H. Clement⁵, Christoph Krafft¹ and Jürgen Popp^1,2,4,*

¹ Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, D-07745 Jena, Germany

² Center for Sepsis Control and Care (CSCC), Jena University Hospital, Erlanger Allee 101, D-07747 Jena, Germany

³ Fraunhofer Institute for Biomedical Engineering (IBMT), Ensheimer Straße 48, D-66386 St. Ingbert, Germany

⁴ Institute of Physical Chemistry and Abbe Center of Photonic, Friedrich-Schiller-University Jena, Helmholtzweg 4, D-07743 Jena, Germany

⁵ Department of Internal Medicine II, Haematology and Medical Oncology, Jena University Hospital, Erlanger Allee 101, D-07747 Jena, Germany

Micromachines 2014, 5(2), 204-215; https://doi.org/10.3390/mi5020204 - 22 Apr 2014

Cited by 16 | Viewed by 10231

Abstract

Circulating tumor cells (CTCs) from blood of cancer patients are valuable prognostic markers and enable monitoring responses to therapy. The extremely low number of CTCs makes their isolation and characterization a major technological challenge. For label-free cell identification a novel combination of Raman [...] Read more.

Circulating tumor cells (CTCs) from blood of cancer patients are valuable prognostic markers and enable monitoring responses to therapy. The extremely low number of CTCs makes their isolation and characterization a major technological challenge. For label-free cell identification a novel combination of Raman spectroscopy with a microhole array platform is described that is expected to support high-throughput and multiplex analyses. Raman spectra were registered from regularly arranged cells on the chip with low background noise from the silicon nitride chip membrane. A classification model was trained to distinguish leukocytes from myeloblasts (OCI-AML3) and breast cancer cells (MCF-7 and BT-20). The model was validated by Raman spectra of a mixed cell population. The high spectral quality, low destructivity and high classification accuracy suggests that this approach is promising for Raman activated cell sorting. Full article

(This article belongs to the Collection Lab-on-a-Chip)

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12 pages, 803 KiB

Open AccessArticle

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

by David Bonzon^1,*, Rodrigo Martinez-Duarte²

, Philippe Renaud¹ and Marc Madou³

¹ Laboratoire de Microsystèmes LMIS4, Ecole Polytechnique Fédérale de Lausanne, Station 17, CH-1015 Lausanne, Switzerland

² Mechanical Engineering Department, Clemson University, 250 Fluor Daniel, Clemson, SC 29634, USA

³ Mechanical and Aerospace Engineering Department, University of California Irvine, 4200 Engineering Gateway, Irvine, CA 92617, USA

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

Cited by 3 | Viewed by 7905

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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11 pages, 3105 KiB

Open AccessArticle

One-Step Combined-Nanolithography-and-Photolithography for a 2D Photonic Crystal TM Polarizer

by Kyung-Hak Choi^1,2,*,†, Jinwoo Huh^3,†, Yonghao Cui¹, Krutarth Trivedi¹, Walter Hu¹, Byeong-Kwon Ju³ and Jeong-Bong Lee¹

¹ Department of Electrical Engineering, The University of Texas at Dallas, Richardson, TX 75080, USA

² Siliconfile Technologies, Inc., Seongnam-si, Gyeonggi-do 463-050, Korea

³ Department of Electrical Engineering, Korea University, Seoul 136-701, Korea

^† These authors contributed equally to this work.

Micromachines 2014, 5(2), 228-238; https://doi.org/10.3390/mi5020228 - 29 Apr 2014

Cited by 8 | Viewed by 9638

Abstract

Photonic crystals have been widely investigated since they have great potential to manipulate the flow of light in an ultra-compact-scale and enable numerous innovative applications. 2D slab photonic crystals for the telecommunication C band at around 1550 nm have multi-scale structures that are [...] Read more.

Photonic crystals have been widely investigated since they have great potential to manipulate the flow of light in an ultra-compact-scale and enable numerous innovative applications. 2D slab photonic crystals for the telecommunication C band at around 1550 nm have multi-scale structures that are typically micron-scale waveguides and deep sub-micron-scale air hole arrays. Several steps of nanolithography and photolithography are usually used for the fabrication of multi-scale photonic crystals. In this work, we report a one-step lithography process to pattern both micron and deep sub-micron features simultaneously for the 2D slab photonic crystal using combined-nanoimprint-and-photolithography. As a demonstrator, a 2D silicon photonic crystal transverse magnetic (TM) polarizer was fabricated, and the operation was successfully demonstrated. Full article

(This article belongs to the Special Issue Micro/Nano Fabrication)

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24 pages, 5856 KiB

Open AccessReview

The Five Ws (and one H) of Super-Hydrophobic Surfaces in Medicine

by Francesco Gentile^1,2,*, Maria Laura Coluccio², Tania Limongi³, Gerardo Perozziello², Patrizio Candeloro²

and Enzo Di Fabrizio^2,3

¹ Istituto Italiano di Tecnologia, 16163 Genova, Italy

² Department of Experimental and Clinical Medicine, University Magna Graecia of Catanzaro, 88100 Catanzaro, Italy

³ Department of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia

Micromachines 2014, 5(2), 239-262; https://doi.org/10.3390/mi5020239 - 5 May 2014

Cited by 12 | Viewed by 10087

Abstract

Super-hydrophobic surfaces (SHSs) are bio-inspired, artificial microfabricated interfaces, in which a pattern of cylindrical micropillars is modified to incorporate details at the nanoscale. For those systems, the integration of different scales translates into superior properties, including the ability of manipulating biological solutions. The [...] Read more.

Super-hydrophobic surfaces (SHSs) are bio-inspired, artificial microfabricated interfaces, in which a pattern of cylindrical micropillars is modified to incorporate details at the nanoscale. For those systems, the integration of different scales translates into superior properties, including the ability of manipulating biological solutions. The five Ws, five Ws and one H or the six Ws (6W), are questions, whose answers are considered basic in information-gathering. They constitute a formula for getting the complete story on a subject. According to the principle of the six Ws, a report can only be considered complete if it answers these questions starting with an interrogative word: who, why, what, where, when, how. Each question should have a factual answer. In what follows, SHSs and some of the most promising applications thereof are reviewed following the scheme of the 6W. We will show how these surfaces can be integrated into bio-photonic devices for the identification and detection of a single molecule. We will describe how SHSs and nanoporous silicon matrices can be combined to yield devices with the capability of harvesting small molecules, where the cut-off size can be adequately controlled. We will describe how this concept is utilized for obtaining a direct TEM image of a DNA molecule. Full article

(This article belongs to the Special Issue Microlenses)

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12 pages, 610 KiB

Open AccessArticle

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

by Prabakaran Saravanan^1,*, Nalam Satyanarayana¹ and Sujeet K. Sinha²

¹ Department of Mechanical Engineering, National University of Singapore, 117576 Singapore

² Department of Mechanical Engineering, Indian Institute of Technology, Kanpur 208016, U.P, India

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

Cited by 2 | Viewed by 7249

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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14 pages, 359 KiB

Open AccessArticle

Fabrication of Polydimethylsiloxane Microlenses Utilizing Hydrogel Shrinkage and a Single Molding Step

by Bader Aldalali^1,2,*, Aditi Kanhere¹, Jayer Fernandes¹, Chi-Chieh Huang¹ and Hongrui Jiang^1,3,4,5,*

¹ Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53707, USA

² Department of Electrical Engineering, Kuwait University, Khaldiya 13060, Kuwait

³ Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53707, USA

⁴ Materials Science Program, University of Wisconsin-Madison, Madison, WI 53707, USA

⁵ McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI 53707, USA

Micromachines 2014, 5(2), 275-288; https://doi.org/10.3390/mi5020275 - 21 May 2014

Cited by 15 | Viewed by 10511

Abstract

We report on polydimethlysiloxane (PDMS) microlenses and microlens arrays on flat and curved substrates fabricated via a relatively simple process combining liquid-phase photopolymerization and a single molding step. The mold for the formation of the PDMS lenses is fabricated by photopolymerizing a polyacrylamide [...] Read more.

We report on polydimethlysiloxane (PDMS) microlenses and microlens arrays on flat and curved substrates fabricated via a relatively simple process combining liquid-phase photopolymerization and a single molding step. The mold for the formation of the PDMS lenses is fabricated by photopolymerizing a polyacrylamide (PAAm) pre-hydrogel. The shrinkage of PAAm after its polymerization forms concave lenses. The lenses are then transferred to PDMS by a single step molding to form PDMS microlens array on a flat substrate. The PAAm concave lenses are also transferred to PDMS and another flexible polymer, Solaris, to realize artificial compound eyes. The resultant microlenses and microlens arrays possess good uniformity and optical properties. The focal length of the lenses is inversely proportional to the shrinkage time. The microlens mold can also be rehydrated to change the focal length of the ultimate PDMS microlenses. The spherical aberration is 2.85 μm and the surface roughness is on the order of 204 nm. The microlenses can resolve 10.10 line pairs per mm (lp/mm) and have an f-number range between f/2.9 and f/56.5. For the compound eye, the field of view is 113°. Full article

(This article belongs to the Special Issue Microlenses)

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11 pages, 741 KiB

Open AccessArticle

A Peristaltic Pump Integrated on a 100% Glass Microchip Using Computer Controlled Piezoelectric Actuators

by Yo Tanaka

Quantitative Biology Center (QBiC), RIKEN, 2-2-3 Minatojima-minamimachi, Chuo, Kobe, Hyogo 650-0047, Japan

Micromachines 2014, 5(2), 289-299; https://doi.org/10.3390/mi5020289 - 23 May 2014

Cited by 43 | Viewed by 10206

Abstract

Lab-on-a-chip technology is promising for the miniaturization of chemistry, biochemistry, and/or biology researchers looking to exploit the advantages of a microspace. To manipulate fluid on a microchip, on-chip pumps are indispensable. To date, there have been several types of on-chip pumps including pneumatic, [...] Read more.

Lab-on-a-chip technology is promising for the miniaturization of chemistry, biochemistry, and/or biology researchers looking to exploit the advantages of a microspace. To manipulate fluid on a microchip, on-chip pumps are indispensable. To date, there have been several types of on-chip pumps including pneumatic, electroactive, and magnetically driven. However these pumps introduce polymers, metals, and/or silicon to the microchip, and these materials have several disadvantages, including chemical or physical instability, or an inherent optical detection limit. To overcome/avoid these issues, glass has been one of the most commonly utilized materials for the production of multi-purpose integrated chemical systems. However, glass is very rigid, and it is difficult to incorporate pumps onto glass microchips. This paper reports the use of a very flexible, ultra-thin glass sheet (minimum thickness of a few micrometers) to realize a pump installed on an entirely glass-based microchip. The pump is a peristaltic-type, composed of four serial valves sealing a cavity with two penetrate holes using ultra-thin glass sheet. By this pump, an on-chip circulating flow was demonstrated by directly observing fluid flow, visualized via polystyrene tracking particles. The flow rate was proportional to the pumping frequency, with a maximum flow rate of approximately 0.80 μL/min. This on-chip pump could likely be utilized in a wide range of applications which require the stability of a glass microchip. Full article

(This article belongs to the Special Issue Micropumps: Design, Fabrication and Applications)

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25 pages, 2242 KiB

Open AccessReview

Fast-Response Liquid Crystal Microlens

by Su Xu¹, Yan Li², Yifan Liu¹, Jie Sun¹, Hongwen Ren³ and Shin-Tson Wu^1,*

¹ CREOL, The College of Optics and Photonics, University of Central Florida, 4000 Central Florida Blvd, Orlando, FL 32816, USA

² National Engineering Lab for TFT-LCD Materials and Technologies, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

³ Department of Polymer-Nano Science and Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756, Korea

Micromachines 2014, 5(2), 300-324; https://doi.org/10.3390/mi5020300 - 3 Jun 2014

Cited by 80 | Viewed by 16807 | Correction

Abstract

Electrically tunable liquid crystal microlenses have attracted strong research attention due to their advantages of tunable focusing, voltage actuation, low power consumption, simple fabrication, compact structure, and good stability. They are expected to be essential optical devices with widespread applications. However, the slow [...] Read more.

Electrically tunable liquid crystal microlenses have attracted strong research attention due to their advantages of tunable focusing, voltage actuation, low power consumption, simple fabrication, compact structure, and good stability. They are expected to be essential optical devices with widespread applications. However, the slow response time of nematic liquid crystal (LC) microlenses has been a significant technical barrier to practical applications and commercialization. LC/polymer composites, consisting of LC and monomer, are an important extension of pure LC systems, which offer more flexibility and much richer functionality than LC alone. Due to the anchoring effect of a polymer network, microlenses, based on LC/polymer composites, have relatively fast response time in comparison with pure nematic LC microlenses. In addition, polymer-stabilized blue phase liquid crystal (PS-BPLC) based on Kerr effect is emerging as a promising candidate for new photonics application. The major attractions of PS-BPLC are submillisecond response time and no need for surface alignment layer. In this paper, we review two types of fast-response microlenses based on LC/polymer composites: polymer dispersed/stabilized nematic LC and polymer-stabilized blue phase LC. Their basic operating principles are introduced and recent progress is reviewed by examples from recent literature. Finally, the major challenges and future perspectives are discussed. Full article

(This article belongs to the Special Issue Microlenses)

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16 pages, 1048 KiB

Open AccessArticle

Wafer-Level Hybrid Integration of Complex Micro-Optical Modules

by Peter Dannberg^*, Frank Wippermann, Andreas Brückner, Andre Matthes, Peter Schreiber and Andreas Bräuer

Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Str. 7, D-07745 Jena, Germany

Micromachines 2014, 5(2), 325-340; https://doi.org/10.3390/mi5020325 - 5 Jun 2014

Cited by 40 | Viewed by 12930

Abstract

A series of technological steps concentrating around photolithography and UV polymer on glass replication in a mask-aligner that allow for the cost-effective generation of rather complex micro-optical systems on the wafer level are discussed. In this approach, optical functional surfaces are aligned to [...] Read more.

A series of technological steps concentrating around photolithography and UV polymer on glass replication in a mask-aligner that allow for the cost-effective generation of rather complex micro-optical systems on the wafer level are discussed. In this approach, optical functional surfaces are aligned to each other and stacked on top of each other at a desired axial distance. They can consist of lenses, achromatic doublets, regular or chirped lens arrays, diffractive elements, apertures, filter structures, reflecting layers, polarizers, etc. The suitability of the separated modules in certain imaging and non-imaging applications will be shown. Full article

(This article belongs to the Special Issue Microlenses)

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18 pages, 2194 KiB

Open AccessArticle

Optimization of Femtosecond Laser Polymerized Structural Niches to Control Mesenchymal Stromal Cell Fate in Culture

by Manuela T. Raimondi¹

, Michele M. Nava¹

, Shane M. Eaton^2,*, Arianna Bernasconi², Krishna C. Vishnubhatla³, Giulio Cerullo² and Roberto Osellame⁴

¹ LaBS, Department of Chemistry, Materials and Chemical Engineering "G. Natta", Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano 20133, Italy

² Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, Milano 20133, Italy

³ Center for Nano Science and Technology of IIT@POLIMI, Via Pascoli 70/3, Milano 20133, Italy, Milano 20133, Italy

⁴ Istituto di Fotonica e Nanotecnologie-Consiglio Nazionale delle Ricerche (IFN-CNR), Piazza Leonardo da Vinci 32, Milano 20133, Italy

Micromachines 2014, 5(2), 341-358; https://doi.org/10.3390/mi5020341 - 11 Jun 2014

Cited by 46 | Viewed by 8499

Abstract

We applied two-photon polymerization to fabricate 3D synthetic niches arranged in complex patterns to study the effect of mechano-topological parameters on morphology, renewal and differentiation of rat mesenchymal stromal cells. Niches were formed in a photoresist with low auto-fluorescence, which enabled the clear [...] Read more.

We applied two-photon polymerization to fabricate 3D synthetic niches arranged in complex patterns to study the effect of mechano-topological parameters on morphology, renewal and differentiation of rat mesenchymal stromal cells. Niches were formed in a photoresist with low auto-fluorescence, which enabled the clear visualization of the fluorescence emission of the markers used for biological diagnostics within the internal niche structure. The niches were structurally stable in culture up to three weeks. At three weeks of expansion in the niches, cell density increased by almost 10-fold and was 67% greater than in monolayer culture. Evidence of lineage commitment was observed in monolayer culture surrounding the structural niches, and within cell aggregates, but not inside the niches. Thus, structural niches were able not only to direct stem cell homing and colony formation, but also to guide aggregate formation, providing increased surface-to-volume ratios and space for stem cells to adhere and renew, respectively. Full article

(This article belongs to the Special Issue Laser Micro- and Nano- Processing)

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14 pages, 661 KiB

Open AccessArticle

Laser Micro Bending Process of Ti6Al4V Square Bar

by Gang Chen and Peng Zhang^*

School of Materials Science and Engineering, Harbin Institute of Technology at Weihai, Weihai 264209, China

Micromachines 2014, 5(2), 359-372; https://doi.org/10.3390/mi5020359 - 11 Jun 2014

Cited by 2 | Viewed by 6674

Abstract

Laser micro bending process of Ti6Al4V square bar are carried out using a 3D thermo-mechanical finite element analytical model (FEM). The transient temperature fields, displacement fields, stress fields and strain fields are obtained and analyzed. The results show that the bending angel during [...] Read more.

Laser micro bending process of Ti6Al4V square bar are carried out using a 3D thermo-mechanical finite element analytical model (FEM). The transient temperature fields, displacement fields, stress fields and strain fields are obtained and analyzed. The results show that the bending angel during laser micro bending process is in good agreement with experimental measurements. The effects of process parameters on temperature and deformation are also investigated here. During the bending process the temperature increases with the increase of the laser power and the irradiation time. Radiation of the laser beam yields to a rapid temperature increase at the irradiated surface, which leads to the high temperature gradients between the irradiated surface and the unirradiated surface, which suggest that the mechanism of laser micro bending is the temperature gradient mechanism. The z displacement of forward direction and reverse direction increase when the laser power and irradiation time increase. Laser micro bending process can obtain the larger bending angles reverse to laser beam using higher laser power and shorter irradiation time. Full article

(This article belongs to the Special Issue Laser Micro- and Nano- Processing)

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12 pages, 2047 KiB

Open AccessArticle

Bio-Inspired Wide-Angle Broad-Spectrum Cylindrical Lens Based on Reflections from Micro-Mirror Array on a Cylindrical Elastomeric Membrane

by Chi-Chieh Huang¹ and Hongrui Jiang^1,2,3,4,*

¹ Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA

² McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, WI 53706 USA

³ Materials Science Program, University of Wisconsin-Madison, Madison, WI 53706, USA

⁴ Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA

Micromachines 2014, 5(2), 373-384; https://doi.org/10.3390/mi5020373 - 20 Jun 2014

Cited by 5 | Viewed by 9588

Abstract

We present a wide-angle, broad-spectrum cylindrical lens based on reflections from an array of three-dimensional, high-aspect-ratio micro-mirrors fabricated on a cylindrical elastomeric substrate, functionally inspired by natural reflecting superposition compound eyes. Our device can perform one-dimensional focusing and beam-shaping comparable to conventional refraction-based [...] Read more.

We present a wide-angle, broad-spectrum cylindrical lens based on reflections from an array of three-dimensional, high-aspect-ratio micro-mirrors fabricated on a cylindrical elastomeric substrate, functionally inspired by natural reflecting superposition compound eyes. Our device can perform one-dimensional focusing and beam-shaping comparable to conventional refraction-based cylindrical lenses, while avoiding chromatic aberration. The focal length of our cylindrical lens is 1.035 mm, suitable for micro-optical systems. Moreover, it demonstrates a wide field of view of 152° without distortion, as well as modest spherical aberrations. Our work could be applied to diverse applications including laser diode collimation, barcode scanning, holography, digital projection display, microlens arrays, and optical microscopy. Full article

(This article belongs to the Special Issue Microlenses)

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11 pages, 1243 KiB

Open AccessArticle

An Experimental Investigation of Micro Pulsating Heat Pipes

by Kai-Shing Yang¹, Yu-Chi Cheng², Ming-Shan Jeng¹, Kuo-Hsiang Chien¹ and Jin-Cherng Shyu^2,*

¹ Green Energy and Environment Research Lab., Industrial Technology Research Institute, Hsinchu 31040, Taiwan

² Department of Mechanical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 80778, Taiwan

Micromachines 2014, 5(2), 385-395; https://doi.org/10.3390/mi5020385 - 20 Jun 2014

Cited by 29 | Viewed by 7243

Abstract

Two Si-based micro pulsating heat pipes (µPHPs) charged using HFE-7100 were either horizontally or vertically oriented and were tested using several heating powers. The width of each channel was 0.8 mm in one µPHP containing uniform channels, and the channel width was 1.0 [...] Read more.

Two Si-based micro pulsating heat pipes (µPHPs) charged using HFE-7100 were either horizontally or vertically oriented and were tested using several heating powers. The width of each channel was 0.8 mm in one µPHP containing uniform channels, and the channel width was 1.0 mm or 0.6 mm in the other µPHP, which did not contain uniform channels. The depth of each channel was 0.25 mm. The overall size of each µPHP was 60 × 10 × 1.25 mm. Visual observation and temperature measurement of the µPHPs under various conditions were performed and the results were analyzed. The results indicated that when the µPHPs were operated horizontally at a heating power ranging from 1 to 7 W, the pulsating two-phase flow in the channels of the µPHPs could not begin, except when the µPHP containing nonuniform channels was tested at a heating power of 7 W. With a heating power less than 5 W, the frequency of the sine-like oscillating displacement of the vapor slug increased and the displacement of the vapor slug reduced in either vertically oriented μPHP, as the heating power increased With a heating power higher than 5 W, periodic “start-stop” behaviors were observed in the vertical μPHP containing nonuniform channels. Full article

(This article belongs to the Special Issue Micro/Nano Fabrication)

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Micromachines, Volume 5, Issue 2 (June 2014) – 19 articles , Pages 116-407

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