Polycarbonate Masters for Soft Lithography

Fabrication of microfluidic devices by soft lithography is by far the most popular approach due to its simplicity and low cost. The approach relies on casting of elastomers, such as polydimethylsiloxane (PDMS), on masters fabricated from photoresists on silicon substrates. These masters, however, can be expensive, complicated to fabricate, and fragile. Here we describe an optimized replica molding approach to preserve the original masters by heat molding of polycarbonate (PC) sheets on PDMS molds. The process is faster and simpler than previously reported methods and does not result in a loss of resolution or aspect ratio for the features. The generated PC masters were used to successfully replicate a wide range of microfluidic devices, including rectangular channels with aspect ratios from 0.025 to 7.3, large area spiral channels, and micropost arrays with 5 µm spacing. Moreover, fabrication of rounded features, such as semi-spherical microwells, was possible and easy. Quantitative analysis of the replicated features showed variability of <2%. The approach is low cost, does not require cleanroom setting or hazardous chemicals, and is rapid and simple. The fabricated masters are rigid and survive numerous replication cycles. Moreover, damaged or missing masters can be easily replaced by reproduction from previously cast PDMS replicas. All of these advantages make the PC masters highly desirable for long-term preservation of soft lithography masters for microfluidic devices.

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High quality diffractive optical elements (DOEs) using SMILE imprint technique

Advanced Optical Technologies ◽

10.1515/aot-2020-0053 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Simon Drieschner ◽

Fabian Kloiber ◽

Marc Hennemeyer ◽

Jan J. Klein ◽

Manuel W. Thesen

Keyword(s):

Soft Lithography ◽

High Efficiency ◽

Low Cost ◽

Industrial Applications ◽

Diffractive Optical Elements ◽

Large Area ◽

High Quality ◽

Optical Elements ◽

Uv Curable ◽

Aspect Ratios

Abstract Augmented reality (AR) enhancing the existing natural environment by overlaying a virtual world is an emerging and growing market and attracts huge commercial interest into optical devices which can be implemented into head-mounted AR equipment. Diffractive optical elements (DOEs) are considered as the most promising candidate to meet the market’s requirements such as compactness, low-cost, and reliability. Hence, they allow building alternatives to large display headsets for virtual reality (VR) by lightweight glasses. Soft lithography replication offers a pathway to the fabrication of large area DOEs with high aspect ratios, multilevel features, and critical dimensions below the diffractive optical limit down to 50 nm also in the scope of mass manufacturing. In combination with tailored UV-curable photopolymers, the fabrication time can be drastically reduced making it very appealing to industrial applications. Here, we illustrate the key features of high efficiency DOEs and how the SMILE (SUSS MicroTec Imprint Lithography Equipment) technique can be used with advanced imprint photopolymers to obtain high quality binary DOEs meeting the market’s requirements providing a very versatile tool to imprint both nano- and microstructures.

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A Very Low-Cost, Labor-Efficient, and Simple Method to Block Scattered Ultraviolet Light in PDMS Microfluidic Devices by Inserting Aluminum Foil Strips

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4041436 ◽

2018 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Shuo Wang ◽

Peter Shankles ◽

Scott Retterer ◽

Yong Tae Kang ◽

Chang Kyoung Choi

Keyword(s):

Soft Lithography ◽

Uv Light ◽

Low Cost ◽

Microfluidic Devices ◽

Aluminum Foil ◽

Material Synthesis ◽

Simple Method ◽

Micro Particles ◽

Complex Shapes ◽

The Cost

Abstract Opto-microfluidic methods have advantages for manufacturing complex shapes or structures of micro particles/hydrogels. Most of these microfluidic devices are made of polydimethylsiloxane (PDMS) by soft lithography because of its flexibility of designing and manufacturing. However, PDMS scatters ultraviolet (UV) light, which polymerizes the photocrosslinkable materials at undesirable locations and clogs the microfluidic devices. A fluorescent dye has previously been employed to absorb the scattered UV light and shift its wavelength to effectively solve this issue. However, this method is limited due to the cost of the materials (tens of dollars per microchip), the time consumed on synthesizing the fluorescent material and verifying its quality (two to three days). More importantly, significant expertise on material synthesis and characterization is required for users of the opto-microfluidic technique. The cost of preliminary testing on multiple iterations of different microfluidic chip designs would also be excessive. Alternatively, with a delicate microchannel design, we simply inserted aluminum foil strips (AFS) inside the PDMS device to block the scattered UV light. By using this method, the UV light was limited to the exposure region so that the opto-microfluidic device could consistently generate microgels longer than 6 h. This is a nearly cost- and labor-free method to solve this issue.

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Micropipette-Based Microfluidic Device for Monodisperse Microbubbles Generation

Micromachines ◽

10.3390/mi9080387 ◽

2018 ◽

Vol 9 (8) ◽

pp. 387

Author(s):

Carlos Toshiyuki Matsumi ◽

Wilson José da Silva ◽

Fábio Kurt Schneider ◽

Joaquim Miguel Maia ◽

Rigoberto E. M. Morales ◽

...

Keyword(s):

Electric Fields ◽

Microfluidic Device ◽

Soft Lithography ◽

Low Cost ◽

Characteristic Curve ◽

Microfluidic Devices ◽

Average Diameter ◽

Internal Diameter ◽

Medical Diagnostic ◽

Average Size

Microbubbles have various applications including their use as carrier agents for localized delivery of genes and drugs and in medical diagnostic imagery. Various techniques are used for the production of monodisperse microbubbles including the Gyratory, the coaxial electro-hydrodynamic atomization (CEHDA), the sonication methods, and the use of microfluidic devices. Some of these techniques require safety procedures during the application of intense electric fields (e.g., CEHDA) or soft lithography equipment for the production of microfluidic devices. This study presents a hybrid manufacturing process using micropipettes and 3D printing for the construction of a T-Junction microfluidic device resulting in simple and low cost generation of monodisperse microbubbles. In this work, microbubbles with an average size of 16.6 to 57.7 μm and a polydispersity index (PDI) between 0.47% and 1.06% were generated. When the device is used at higher bubble production rate, the average diameter was 42.8 μm with increased PDI of 3.13%. In addition, a second-order polynomial characteristic curve useful to estimate micropipette internal diameter necessary to generate a desired microbubble size is presented and a linear relationship between the ratio of gaseous and liquid phases flows and the ratio of microbubble and micropipette diameters (i.e., Qg/Ql and Db/Dp) was found.

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Reshaping Hybrid Perovskites Emission with Flexible Polymer Microcavities

EPJ Web of Conferences ◽

10.1051/epjconf/202023000006 ◽

2020 ◽

Vol 230 ◽

pp. 00006

Author(s):

Paola Lova ◽

Paolo Giusto ◽

Francesco Di Stasio ◽

Giovanni Manfredi ◽

Giuseppe M. Paternò ◽

...

Keyword(s):

Thin Films ◽

Photonic Crystals ◽

Low Cost ◽

Scale Production ◽

Large Area ◽

Light Emitting Devices ◽

Flexible Polymer ◽

Hybrid Perovskite ◽

Wide Range ◽

Solution Processable

Thanks to versatile optoelectronic properties solution processable perovskites have attracted increasing interest as active materials in photovoltaic and light emitting devices. However, the deposition of perovskite thin films necessitates wide range solvents that are incompatible with many other solution-processable media, including polymers that are usually dissolved by the perovskite solvents. In this work, we demonstrate that hybrid perovskite thin films can be coupled with all polymer planar photonic crystals with different approaches to achieve emission intensity enhancement and reshaping using different approaches. The possibility to control and modify the emission spectrum of a solution processable perovskite via a simple spun-cast polymer structure is indeed of great interest in optoelectronic applications requiring high color purity or emission directionality. Furthermore, thanks to the ease of fabrication and scalability of solution-processed photonic crystals, this approach could enable industrial scale production of low-cost, large area, lightweight and flexible polymer-perovskite lighting devices, which may be tuned without resorting to compositional engineering.

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Fabrication of Rough Polymer Surfaces Exhibiting Anti-reflective Properties

MRS Proceedings ◽

10.1557/opl.2015.190 ◽

2015 ◽

Vol 1728 ◽

Author(s):

Srinadh Mattaparthi ◽

Chandra S. Sharma

Keyword(s):

Solar Cells ◽

Soft Lithography ◽

Electrospun Nanofibers ◽

Polymer Surfaces ◽

Large Area ◽

Engineering Applications ◽

Pdms Surface ◽

Hierarchical Roughness ◽

Vis Spectroscopy ◽

Wide Range

ABSTRACTWe have demonstrated some facile ways to fabricate the large area polymer surfaces with varying roughness followed by studying their anti-reflective properties. One of the approaches is based on electrospun nanofibers deposited on a substrate in an uneven non-woven matrix. This electrospun fabric was used as a master template to fabricate the negative replica of the fibers by soft lithography generating the roughness in polydimethylsiloxane (PDMS) surfaces. The second approach is based on biomimicking of flower petals. Petals are used as a master template to transfer surface features with hierarchical roughness over PDMS surface using replica moulding. As fabricated polymer surfaces with varied roughness have then tested for their anti-reflective properties using UV-VIS spectroscopy over a wide range of wavelengths and angles of incidence of light. These measurements show near zero reflection of patterned PDMS surfaces as compared to planar PDMS. This omnidirectional broadband anti-reflection behaviour of polymer surfaces can be used in wide variety of engineering applications including in solar cells.

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Cryopreservation and transplantation of common carp spermatogonia

10.1101/429449 ◽

2018 ◽

Cited By ~ 1

Author(s):

Roman Franěk ◽

Zoran Marinović ◽

Jelena Lujić ◽

Béla Urbányi ◽

Michaela Fučíková ◽

...

Keyword(s):

Common Carp ◽

Sperm Cryopreservation ◽

Post Transplantation ◽

Wide Range ◽

Cultured Fish ◽

The World ◽

Exogenous Origin ◽

Long Term Preservation ◽

Surrogate Production

AbstractCommon carp (Cyprinus carpio) is one of the most cultured fish species over the world with many different breeds and plenty of published protocols for sperm cryopreservation, however, data regarding preservation of gonadal tissue and surrogate production is still missing. A protocol for freezing common carp spermatogonia was developed through varying different factors along a set of serial subsequent experiments. Among the six cryoprotectants tested, the best survival was achieved with dimethyl sulfoxide (Me2SO). In the next experiment, a wide range of cooling rates (0.5–10 °C/min) and different concentrations of Me2SO were tested resulting in the highest survival using 2 M Me2SO and cooling rate of –1 Q59 A When testing different tissue sizes and incubation times in the cryomedium, the highest viability was observed when incubating 100 mg tissue fragments for 30 min. Finally, sugar supplementation did not yield significant differences. When testing different equilibration (ES) and vitrification solutions (VS) used for needle-immersed vitrification, no significant differences were observed between the tested groups. Additionally, varied exposure time to VS did not improve the vitrification outcome where the viability was 4-fold lower than that of freezing. The functionality of cryopreserved cells was tested by interspecific transplantation into sterilized goldfish recipients. The exogenous origin of the gonads in goldfish recipients was confirmed by molecular markers and incorporation rate was over 40% in both groups at 3 months post transplantation. Results of this study can serve as an alternative way for long-term preservation of germplasm in carp which can be recovered in a surrogate recipient.

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Enhanced Surface Properties of Light-Trapping Si Nanowires Using Synergetic Effects of Metal-Assisted and Anisotropic Chemical Etchings

Scientific Reports ◽

10.1038/s41598-019-52382-4 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Youngsoon Jeong ◽

Chanwoo Hong ◽

Yeong Hun Jung ◽

Rashida Akter ◽

Hana Yoon ◽

...

Keyword(s):

Interfacial Energy ◽

Chemical Etching ◽

Low Cost ◽

Light Trapping ◽

Si Nanowires ◽

Si Substrate ◽

Large Area ◽

Aspect Ratios ◽

Energy States ◽

Si Nanostructures

Abstract Metal-assisted chemical etching (MACE) has been widely explored for developing silicon (Si)-based energy and optical devices with its benefits for low-cost and large-area fabrication of Si nanostructures of high aspect ratios. Surface structures and properties of Si nanostructures fabricated through MACE are significantly affected by experimental and environmental conditions of etchings. Herein, we showed that surfaces and interfacial energy states of fabricated Si nanowires can be critically affected by oxidants of MACE etching solutions. Surfaces of fabricated Si nanowires are porous and their tips are fully covered with lots of Si nano-sized grains. Strongly increased photoluminescence (PL) intensities, compared to that of the crystalline Si substrate, are observed for MACE-fabricated Si nanowires due to interfacial energy states of Si and SiOx of Si nano-sized grains. These Si grains can be completely removed from the nanowires by an additional etching process of the anisotropic chemical etching (ACE) of Si to taper the nanowires and enhance light trapping of the nanowires. Compared with the MACE-fabricated Si nanowires, ACE-fabricated tapered Si nanowires have similar Raman and PL spectra to those of the crystalline Si substrate, indicating the successful removal of Si grains from the nanowire surfaces by the ACE process.

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3D-printable cell crowding device enables imaging of live cells in compression

BioTechniques ◽

10.2144/btn-2019-0160 ◽

2020 ◽

Vol 68 (5) ◽

pp. 275-278

Author(s):

Liam P Dow ◽

Aimal H Khankhel ◽

John Abram ◽

Megan T Valentine

Keyword(s):

Low Cost ◽

Optical Microscope ◽

Live Cells ◽

Epithelial Monolayers ◽

Low Profile ◽

Wide Range ◽

Multiple Devices ◽

Microscopy Techniques ◽

High Resolution Microscopy

We designed and fabricated, using low-cost 3D printing technologies, a device that enables direct control of cell density in epithelial monolayers. The device operates by varying the tension of a silicone substrate upon which the cells are adhered. Multiple devices can be manufactured easily and placed in any standard incubator. This allows long-term culturing of cells on pretensioned substrates until the user decreases the tension, thereby inducing compressive forces in plane and subsequent instantaneous cell crowding. Moreover, the low-profile device is completely portable and can be mounted directly onto an inverted optical microscope. This enables visualization of the morphology and dynamics of living cells in stretched or compressed conditions using a wide range of high-resolution microscopy techniques.

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A new low-cost method for long-term preservation of filamentous fungi

Biocatalysis and Agricultural Biotechnology ◽

10.1016/j.bcab.2019.101417 ◽

2019 ◽

Vol 22 ◽

pp. 101417 ◽

Cited By ~ 1

Author(s):

Osama A. Al-Bedak ◽

Rania M. Sayed ◽

Sedky H.A. Hassan

Keyword(s):

Filamentous Fungi ◽

Low Cost ◽

Long Term Preservation

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The Effect of Heater Size, Location, Aspect Ratio, and Boundary Conditions on Two-Dimensional, Laminar, Natural Convection in Rectangular Channels

Journal of Heat Transfer ◽

10.1115/1.3450518 ◽

1976 ◽

Vol 98 (2) ◽

pp. 194-201 ◽

Cited By ~ 114

Author(s):

H. H.-S. Chu ◽

S. W. Churchill ◽

C. V. S. Patterson

Keyword(s):

Vertical Wall ◽

Alternating Direction Implicit ◽

Aspect Ratios ◽

Alternating Direction ◽

Rectangular Channels ◽

Wide Range ◽

Localized Heating ◽

Laminar Natural Convection ◽

Lower Temperature ◽

Limiting Case

The effect of localized heating in rectangular channels was studied by solving the partial differential equations for the conservation of mass, momentum, and energy numerically using an unsteady state formulation and the alternating-direction-implicit method. The heating element was a long, horizontal, isothermal strip located in one, otherwise-insulated vertical wall. The opposing wall was maintained at a lower uniform temperature and the upper and lower surfaces were insulated or maintained at the lower temperature. Computations were carried out for Pr = 0.7, 0 ≤ Ra ≤ 105, a complete range of heater widths and locations and a wide range of aspect ratios. Flow visualization studies and comparison with prior computed results for a limiting case confirm the validity of the computed values. The computed rates of heat transfer and circulation provide guidance for locating heaters or coolers.

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